w 1 OrcaFlex Manual Version 9.6a Orcina Ltd. Daltongate Ulverston Cumbria LA12 7AJ UK Telephone:+44 (0) 1229 584742 Fax:+44 (0) 1229 587191 E-mail:orcina@orcina.com Web Site:www.orcina.comw Contents 3 CONTENTS 1INTRODUCTION11 1.1Installing OrcaFlex11 1.2Running OrcaFlex13 1.3Parallel Processing14 1.4Distributed OrcaFlex15 1.5Orcina Licence Monitor15 1.6Demonstration Version15 1.7OrcaFlex Examples15 1.8Validation and QA15 1.9Orcina15 1.10References and Links16 2TUTORIAL21 2.1Getting Started21 2.2Building a Simple System21 2.3Adding a Line21 2.4Adjusting the View22 2.5Static Analysis22 2.6Dynamic Analysis23 2.7Multiple Views23 2.8Looking at Results24 2.9Getting Output24 2.10Input Data24 3USER INTERFACE25 3.1Introduction25 3.1.1Program Windows25 3.1.2The Model25 3.1.3Model States26 3.1.4Toolbar27 3.1.5Status Bar28 3.1.6Mouse and Keyboard Actions28 3.2OrcaFlex Model Files31 3.2.1Data Files31 3.2.2Text Data Files32 3.2.3Simulation Files36 3.3Model Browser37 3.3.1Model Browser Views39 3.3.2Move Selected Objects Wizard39 Contents w 4 3.4Libraries40 3.4.1Using Libraries41 3.4.2Building a Library44 3.5Menus44 3.5.1File Menu45 3.5.2Edit Menu46 3.5.3Model Menu46 3.5.4Calculation Menu48 3.5.5View Menu49 3.5.6Replay Menu49 3.5.7Graph Menu50 3.5.8Results Menu50 3.5.9Tools Menu50 3.5.10Workspace Menu51 3.5.11Window Menu51 3.5.12Help Menu52 3.63D Views52 3.6.1View Parameters53 3.6.2View Control54 3.6.3Navigating in 3D Views54 3.6.4Shaded Graphics55 3.6.5How Objects are Drawn57 3.6.6Selecting Objects59 3.6.7Creating and Destroying Objects59 3.6.8Dragging Objects59 3.6.9Connecting Objects59 3.6.10Printing, Copying and Exporting Views60 3.7Replays60 3.7.1Replay Parameters60 3.7.2Replay Control61 3.7.3Custom Replays62 3.7.4Custom Replay Wizard62 3.8Data Forms63 3.8.1Data Fields64 3.8.2Data Form Editing65 3.9Results66 3.9.1Producing Results66 3.9.2Selecting Variables68 3.9.3Summary and Full Results68 3.9.4Statistics69 3.9.5Linked Statistics69 3.9.6Offset Tables69 3.9.7Line Clashing Report70 3.9.8Time History and XY Graphs71 3.9.9Range Graphs72 3.9.10Offset Graphs73 3.9.11Spectral Response Graphs73 3.9.12Extreme Value Statistics Results73 w Contents 5 3.9.13Presenting OrcaFlex Results76 3.10Graphs77 3.10.1Modifying Graphs78 3.11Spreadsheets79 3.12Text Windows79 3.13Workspaces79 3.14Comparing Data80 3.15Preferences81 3.16Printing and Exporting83 4AUTOMATION85 4.1Introduction85 4.2Batch Processing85 4.2.1Introduction85 4.2.2Script Files87 4.2.3Script Syntax87 4.2.4Script Commands87 4.2.5Examples of setting data91 4.2.6Handling Script Errors96 4.2.7Obtaining Variable Names97 4.2.8Automating Script Generation97 4.3Text Data Files99 4.3.1Examples of setting data99 4.3.2Automating Generation106 4.4Post-processing107 4.4.1Introduction107 4.4.2OrcaFlex Spreadsheet107 4.4.3Instruction Format111 4.4.4Pre-defined commands112 4.4.5Basic commands113 4.4.6Time History and related commands114 4.4.7Range Graph commands115 4.4.8Data commands115 4.4.9Instructions Wizard116 4.4.10Duplicate Instructions119 5THEORY123 5.1Coordinate Systems123 5.2Direction Conventions124 5.3Object Connections125 5.4Interpolation Methods125 5.5Static Analysis127 5.5.1Line Statics127 5.5.2Buoy and Vessel Statics131 5.5.3Vessel Multiple Statics131 Contents w 6 5.6Dynamic Analysis132 5.6.1Calculation Method133 5.6.2Ramping135 5.7Friction Theory135 5.8Spectral Response Analysis138 5.9Extreme Value Statistics Theory139 5.10Environment Theory141 5.10.1Buoyancy Variation with Depth141 5.10.2Current Theory141 5.10.3Seabed Theory142 5.10.4Seabed Non-Linear Soil Model Theory143 5.10.5Morison's Equation149 5.10.6Waves150 5.11Vessel Theory157 5.11.1Vessel Rotations157 5.11.2RAOs and Phases158 5.11.3RAO Quality Checks160 5.11.4Current and Wind Loads161 5.11.5Stiffness, Added Mass and Damping164 5.11.6Impulse Response and Convolution165 5.11.7Wave Drift and Sum Frequency Loads166 5.11.8Manoeuvring Load171 5.11.9Other Damping171 5.12Line Theory172 5.12.1Overview172 5.12.2Structural Model Details174 5.12.3Calculation Stages175 5.12.4Calculation Stage 1 Tension Forces175 5.12.5Calculation Stage 2 Bend Moments176 5.12.6Calculation Stage 3 Shear Forces179 5.12.7Calculation Stage 4 Torsion Moments179 5.12.8Calculation Stage 5 Total Load180 5.12.9Line End Orientation180 5.12.10Line Local Orientation181 5.12.11Treatment of Compression181 5.12.12Contents Flow Effects182 5.12.13Line Pressure Effects183 5.12.14Pipe Stress Calculation184 5.12.15Pipe Stress Matrix185 5.12.16Hydrodynamic and Aerodynamic Loads187 5.12.17Drag Chains189 5.12.18Line End Conditions191 5.12.19Interaction with the Sea Surface191 5.12.20Interaction with Seabed and Shapes192 5.12.21Clashing192 5.136D Buoy Theory195 5.13.1Overview195 5.13.2Lumped Buoy Added Mass, Damping and Drag197 w Contents 7 5.13.3Spar Buoy and Towed Fish Added Mass and Damping198 5.13.4Spar Buoy and Towed Fish Drag201 5.13.5Slam Force203 5.13.6Contact Forces205 5.143D Buoy Theory205 5.15Winch Theory206 5.16Shape Theory208 6SYSTEM MODELLING: DATA AND RESULTS211 6.1Modelling Introduction211 6.2Data in Time History Files212 6.3Variable Data214 6.3.1External Functions215 6.4General Data217 6.4.1Statics217 6.4.2Dynamics219 6.4.3Integration & Time Steps220 6.4.4Explicit Integration220 6.4.5Implicit Integration222 6.4.6Numerical Damping223 6.4.7Response Calculation223 6.4.8Results223 6.4.9Drawing224 6.4.10Properties Report224 6.5Environment225 6.5.1Sea Data225 6.5.2Sea Density Data226 6.5.3Seabed Data227 6.5.4Wave Data230 6.5.5Data for Regular Waves232 6.5.6Data for Random Waves232 6.5.7Data for JONSWAP and ISSC Spectra233 6.5.8Data for Ochi-Hubble Spectrum234 6.5.9Data for Torsethaugen Spectrum235 6.5.10Data for Gaussian Swell Spectrum235 6.5.11Data for User Defined Spectrum235 6.5.12Data for Time History Waves236 6.5.13Data for User Specified Components237 6.5.14Data for Response Calculation237 6.5.15Waves Preview237 6.5.16Modelling Design Waves238 6.5.17Setting up a Random Sea240 6.5.18Current Data242 6.5.19Wind Data244 6.5.20Drawing Data245 6.5.21External Functions246 6.5.22Results246 Contents w 8 6.5.23Wave Scatter Conversion247 6.6Solid Friction Coefficients Data251 6.7Vessels252 6.7.1Vessel Modelling Overview254 6.7.2Vessel Data255 6.7.3Vessel Types264 6.7.4Modelling Vessel Slow Drift292 6.7.5Vessel Response Reports294 6.7.6Vessel Results296 6.8Lines300 6.8.1Line Data302 6.8.2Line Types318 6.8.3Attachments330 6.8.4Line Contact334 6.8.5Rayleigh Damping340 6.8.6P-y Models343 6.8.7Line Results346 6.8.8Drag Chain Results358 6.8.9Flex Joint Results359 6.8.10Line Setup Wizard359 6.8.11Line Type Wizard360 6.8.12Chain361 6.8.13Rope/Wire366 6.8.14Line with Floats369 6.8.15Homogeneous Pipe373 6.8.16Hoses and Umbilicals375 6.8.17Modelling Stress Joints377 6.8.18Modelling Bend Restrictors379 6.8.19Modelling non-linear homogeneous pipes381 6.8.20Line Ends383 6.8.21Modelling Compression in Flexibles386 6.96D Buoys387 6.9.1Wings388 6.9.2Common Data389 6.9.3Applied Loads391 6.9.4Wing Data391 6.9.5Wing Type Data392 6.9.6Lumped Buoy Properties394 6.9.7Lumped Buoy Drawing Data395 6.9.8Spar Buoy and Towed Fish Properties396 6.9.9Spar Buoy and Towed Fish Drag & Slam398 6.9.10Spar Buoy and Towed Fish Added Mass and Damping399 6.9.11Spar Buoy and Towed Fish Drawing400 6.9.12Shaded Drawing401 6.9.13Other uses403 6.9.14External Functions403 6.9.15Properties Report403 6.9.16Results404 6.9.17Buoy Hydrodynamics407 w Contents 9 6.9.18Hydrodynamic Properties of a Rectangular Box407 6.9.19Modelling a Surface-Piercing Buoy410 6.103D Buoys412 6.10.1Data413 6.10.2Properties Report414 6.10.3Results414 6.11Winches415 6.11.1Data416 6.11.2Wire Properties416 6.11.3Control417 6.11.4Control by Stage417 6.11.5Control by Whole Simulation419 6.11.6Drive Unit419 6.11.7External Functions419 6.11.8Results419 6.12Links420 6.12.1Data421 6.12.2Results422 6.13Shapes423 6.13.1Data424 6.13.2Blocks425 6.13.3Cylinders426 6.13.4Curved Plates426 6.13.5Planes427 6.13.6Drawing428 6.13.7Results429 6.14All Objects Data Form429 7MODAL ANALYSIS431 7.1Data and Results431 7.2Theory432 8FATIGUE ANALYSIS435 8.1Introduction435 8.2Commands436 8.3Data437 8.4Load Cases Data for Regular Analysis438 8.5Load Cases Data for Rainflow Analysis439 8.6Load Cases Data for Spectral Analysis439 8.7Load Cases Data for SHEAR7441 8.8Components Data441 8.9Analysis Data442 8.10S-N and T-N Curves443 8.11Integration Parameters444 Contents w 10 8.12Results444 8.13Automation445 8.14Fatigue Points446 8.15How Damage is Calculated446 9VIV TOOLBOX449 9.1Frequency Domain Models449 9.1.1VIVA449 9.1.2SHEAR7453 9.2Time Domain Models460 9.2.1Wake Oscillator Models463 9.2.2Vortex Tracking Models466 9.2.3VIV Drawing472 w Introduction, Installing OrcaFlex 11 1INTRODUCTION WelcometoOrcaFlex(version9.6a),amarinedynamicsprogramdevelopedbyOrcinaforstaticanddynamic analysis of a wide range of offshore systems, including all types of marine risers (rigid and flexible), global analysis, moorings, installation and towed systems. OrcaFlexprovidesfastandaccurateanalysisof catenarysystemssuchasflexiblerisersandumbilicalcablesunder waveandcurrentloadsandexternallyimposedmotions.OrcaFlexmakesextensiveuseofgraphicstoassist understanding.Theprogramcanbeoperatedinbatchmodeforroutineanalysisworkandtherearealsospecial facilities for post-processing your results including fully integrated fatigue analysis capabilities. OrcaFlexisafully3Dnon-lineartimedomainfiniteelementprogramcapableofdealingwitharbitrarilylarge deflections of the flexible from the initial configuration. A lumped mass element is used which greatly simplifies the mathematicalformulationandallowsquickandefficientdevelopmentoftheprogramtoincludeadditionalforce terms and constraints on the system in response to new engineering requirements. Inadditiontothetimedomainfeatures,modalanalysiscanbeperformedforeitherthewholesystemorfor individual lines. RAOs can be calculated for any results variable using the Spectral Response Analysis feature. OrcaFlex is also used for applications in the Defence, Oceanography and Renewable energy sectors. OrcaFlex is fully 3Dandcanhandlemulti-linesystems,floatinglines,linedynamicsafterrelease,etc.Inputsincludeshipmotions, regular and random waves. Results output includes animated replay plus full graphical and numerical presentation. If you are new to OrcaFlex then please see the tutorial and examples. For further details of OrcaFlex and our other software, please contact Orcina or your Orcina agent. Copyright notice Copyright Orcina Ltd. 1987-2012. All rights reserved. 1.1INSTALLING ORCAFLEX Hardware Requirements OrcaFlex can be installed and run on any computer that has: -WindowsXP,WindowsVista,Windows7orWindows8.Both32bitand64bitversionsofWindowsare supported. -If you are using small fonts (96dpi) the screen resolution must be at least 1024768. If you are using large fonts (120dpi) the screen resolution must be at least 12801024. However, OrcaFlex is a powerful package and to get the best results we would recommend: -A 64 bit edition of Windows 7 or later. -A powerful processor with fast floating point and memory performance. This is the most important factor since OrcaFlex is a computation-intensive program and simulation run times can be long for complex models. -Atleast4GBofmemory.ThisislessimportantthanprocessorperformancebutsomeaspectsofOrcaFlexdo performbetterwhenmorememoryisavailable,especiallyonmulti-coresystems.Ifyouhaveamulti-core system with a 64 bit version of Windows then you may benefit from fitting even more memory. -A multi-core system to take advantage of OrcaFlex's multi-threading capabilities. -As much disk space as you require to store simulation files. Simulation files vary in size, but can be hundreds of megabytes each for complex models. -A screen resolution of 12801024 or greater with 32 bit colour. -ADirectX9compatiblegraphicscardwithatleast256MBmemoryforthemosteffectiveuseoftheshaded graphics facility. -MicrosoftExcel(Excel2000,orlater)inordertousetheOrcaFlexautomationfacilities.Both32bitand64bit versions of Excel are supported. Installation To install OrcaFlex: Introduction, Installing OrcaFlex w 12 -You will need to install from an account with administrator privileges. -Ifinstallingfromdisc,inserttheOrcaFlexinstallationdiscandruntheAutorun.exeprogramonthedisc(on many machines this program will run automatically when you insert the disc). Then click on 'Install OrcaFlex'.-IfyouhavereceivedOrcaFlexbye-mailorfromthewebyouwillhaveazipfile,andpossiblyanumberof licence files (.lic). Extract the files from the zip file to some temporary location, and save the licence files to the same folder. Then run the extracted file Setup.exe. -You will also need to install the OrcaFlex dongle supplied by Orcina. See below for details. For further details, including information on network and silent installation, click on Read Me on the Autorun menu or open the file Installation Guide.pdf on the disc. If you have any difficulty installing OrcaFlex please contactOrcina or your Orcina agent. Orcina Shell Extension WhenyouinstallOrcaFlextheOrcinaShellExtensionisalsoinstalled.ThisintegrateswithWindowsExplorer,and associatesthedataandsimulationfiletypes(.datand.sim)withOrcaFlex.YoucanthenopenanOrcaFlexfileby simply double-clicking the filename in Explorer.The shell extension also provides file properties information, such aswhichversionof OrcaFlexwrotethefileandtheCommentstext forthemodelinthefile.Fordetailsseethefile OrcShlEx\ReadMe.htm on the OrcaFlex installation disc. Installing the Dongle OrcaFlex is supplied with a dongle, a small hardware device that must be attached to the machine or to the network to which the machine is attached. Note:Thedongleiseffectivelyyourlicencetorunonecopy(ormore,ifthedongleisenabledformore copies)ofOrcaFlex.Itis,inessence,whatyouhavepurchasedorleased,anditshouldbetreated with appropriate care and security. If you lose your dongle you cannot run OrcaFlex. Warning:Orcina can normally resupply disks or manuals (a charge being made to cover costs) if they are lost or damaged. But we can only supply a newdonglein the case where the olddongleis returned to us. Dongleslabelled'Hxxx'(wherexxxisthedonglenumber)mustbepluggedintothemachineonwhichOrcaFlexis run.Dongleslabelled'Nxxx'canbeusedinthesamewayas'Hxxx'dongles,buttheycanalsobeusedovera network,allowingtheprogramtobesharedbymultipleusers.Inthelattercasethedongleshouldbeinstalledby your network administrator; instructions can be found in the Dongle directory on the OrcaFlex installation disc. Types of Dongle DonglesareavailableforeitherparallelorUSBports,andthesearefunctionallyequivalentsofarasOrcaFlexis concerned. In general, USB dongles are preferred, since they seem to be more reliable. In any case, parallel ports are becoming less common on new machines. By default, 'N' dongles can hold up to 10 OrcaFlex licences for use over a network. We can supply dongles with larger capacities on request. Dongle Troubleshooting Wesupply,withOrcaFlex,adongleutilityprogramcalledOrcaDongle.IfOrcaFlexcannotfindthedonglethenthis programmaybeusedtocheckthatthedongleisworkingcorrectlyandhastheexpectednumberoflicences.For details see the OrcaDongle help file. TheOrcaDongleprogramisincludedontheOrcaFlexinstallationdisc,andyoumaychoosetoinstallitfromthe AutorunmenuinthesamewayasOrcaFlex.Itisalsoavailablefordownloadfrom www.orcina.com/Support/Dongle. Alsoonourwebsite,usersofnetworkdonglesmayfindtheOrcinaLicenceMonitortobeuseful.Thisapplication keeps track of the number of OrcaFlex licences claimed on a network at any time. Diagnostics If OrcaFlex fails to start, with the error that it can't obtain a licence, then please check the following.-Ifyouareusinganetworkdongle,areallthelicencesinuse?TheOrcinaLicenceMonitormaybeofusein determining this. If they are, you will need to wait until a licence becomes free before you can run OrcaFlex.w Introduction, Running OrcaFlex 13 -If you are using a local dongle, is it plugged into yourmachine? If so, is the dongledevice driver installed? You cancheckthisbyrunningOrcaDongle.Ifthedriverisnotpresent,itmayhavebeenuninstalledbyanother program:ifso,youcanfixthisbyRepairingtheOrcaFlexinstallation(fromtheWindowsControlPanel,select 'Add or Remove Programs' (XP) or Programs / Programs and Features (Vista), select the OrcaFlex entry, select Change then Repair). If this still fails, you can install the driver by downloading from ourwebsite, and running, the file Hasp-Setup.msi. -Does the dongle you are using have an OrcaFlex licence on it? Again, you can check this with OrcaDongle. -Do you have a licence file for the dongle you wish to access? This file will be named Nxxx.lic or Hxxx.lic (where xxx is the dongle number) and will be in the OrcaFlex installation folder. If not, then you should be able to copy the required file(s) from the root level of the OrcaFlex installation disc into the installation folder. If none of these help, then please contact us at Orcina with a description of the problem. Ideally, please also email to us the diagnostics file named OrcLog.txt which OrcaFlex will have written on failing to find a licence. This file can be found in the folder "%appdata%/Orcina/OrcaFlex": to open this folder, select Start menu | Run and enter the text between the quotes (including the '%' characters).1.2RUNNING ORCAFLEX AshortcuttorunOrcaFlexissetupontheStartmenuwhenyouinstallOrcaFlex(seeStart\Programs\Orcina Software\). ThisshortcutpassesnoparameterstoOrcaFlexsoitgivesthedefaultstart-upbehaviour;seebelow.Ifthisisnot suitableyoucanconfigurethestart-upbehaviour usingcommand-lineparameters,forexamplebysettingup your own shortcuts with particular parameter settings. Default Start-up OrcaFlexhastwobasicmodules:fullOrcaFlexandstatics-onlyOrcaFlex.AfullOrcaFlexlicenceisneededfor dynamic analysis. WhenyourunOrcaFlexitlooksforanOrcinadonglefromwhichitcanclaimanOrcaFlexlicence(eitherafull licenceorastatics-onlylicence).Bydefault,itfirstlooksforalicenceonalocaldongle(i.e.oneinlocalmodeand connectedtothelocalmachine)andifnoneisfoundthenitlooksforalicenceonanetworkdongle(i.e.onein networkmodeandaccessedviaalicencemanageroverthenetwork).Thisdefaultbehaviourcanbechangedby command-line parameters. If OrcaFlex finds a network dongle and there is a choice of which licences to claim from it, then OrcaFlex displays a Choose Modulesdialogtoaskyouwhichmodulesyouwanttoclaim. Thishelpsyousharethelicenceswithother usersofthatnetworkdongle.Forexampleifthenetworkdonglecontainsbothafulllicenceandastatics-only licence then you can choose to use the statics-only licence, if that is all you need, so that the full licence is left free for others to use when you do not need it yourself. The Choose Modules dialog can be suppressed usingcommand-line parameters. Command Line Parameters OrcaFlex can accept various parameters on the command line to modify the way it starts up. The syntax is: OrcaFlex.exe Filename Option1 Option2 etc. Filename is optional. If present it should be the name of an OrcaFlex data file (.dat or .yml) or simulation file (.sim). After starting up OrcaFlex will automatically open that file. Option1,Option2etc.areoptionalparametersthatallowyouconfigurethestart-up behaviour.Theycanbeanyof thefollowingswitches.Forthefirstcharacterofanoptionswitch,thehyphencharacter'-'canbeusedasan alternative to the '/' character. Dongle Search switches By default the program searches first for a licence on a local dongle and then for a licence on a network dongle. The following switches allow you to modify this default behaviour. -/LocalDongle Only search for licences on a local dongle. No search will be made for network dongles. -/NetworkDongleOnlysearchforlicencesonanetworkdongle.Anylocaldonglewillbeignored.Thiscanbe useful if you have a local dongle but want to use a network dongle that has licences for more modules. Introduction, Parallel Processing w 14 Module Choice switch Thisswitchisonlyrelevantif thedonglefoundisanetworkdongleandthereisachoiceof licencestoclaimfrom that dongle. You can specify your choice using the following command line switch: -/DisableDynamics Choose the statics-only basic licence. This is sometimes useful when using a network dongle since it allows you to leave full licences free for other users when you only need a statics-only licence. If you do not specify all the choices then the program displays theChoose Modules dialog to ask for your remaining choices. You can suppress this dialog using the following switch. -/DisableInteractiveStartupDonotdisplaytheChooseModulesdialog.Theprogrambehavesthesameasif the user clicks OK on that dialog without changing any module choices. Batch Calculation switches TheseswitchesallowyoutoinstructOrcaFlextostartabatchcalculationassoonastheprogramhasloaded.The following switches are available: -/BatchStartabatchcalculationassoonastheprogramhasloaded.Thebatchcalculationwillcontainallthe files specified on the command line (you can have more than one) in the order in which they are specified. You can use relative paths which will be relative to the working directory. -/CloseAfterBatch Instructs the program to close once the batch is complete. -/BatchAnalysisStatics, /BatchAnalysisDynamics specify what type of analysis to perform to the specified files. If these parameters are missing then the program defaults to dynamic analysis. -/FileList instructs the program that any text files specified on the command line contain a list of files to include in thebatch calculation. The command line can containmore than onefile list. Text files within the file listwill be treated as batch script files. Process Priority switches TheseswitchesdeterminetheprocessingpriorityofOrcaFlex.Theavailableswitchesare/RealtimePriority, /HighPriority, /AboveNormalPriority, /NormalPriority, /BelowNormalPriority, /LowPriority. ThickLines switch The /ThickLines switch allows you to specify a minimum thickness for lines drawn on OrcaFlex 3D View windows. For example using the switch /ThickLines=5 forces OrcaFlex to draw all lines at a thickness of at least 5. If no value is specified (i.e. the switch is /ThickLines) then the minimum thickness is taken to be 2. This switch has been added to make OrcaFlex 3D Views clearer when projected onto a large screen.ThreadCount switch The/ThreadCountswitchallowsyoutosetthenumberofexecutionthreadsusedbyOrcaFlexforparallel processing.Forexample/ThreadCount=1forcesOrcaFlextouseasingleexecutionthreadwhichhastheeffectof disabling parallel processing. 1.3PARALLEL PROCESSING Machines with multiple processors or processors with multiple cores are becoming increasingly common. OrcaFlex can make good use of the additional processing capacity afforded by such machines. For up to date information on hardware choice for OrcaFlex please refer to www.orcina.com/Support/Benchmark. OrcaFlexperformsthecalculationsofthemodel'sLineobjectsinparallel.Thismeansthat,interactivelyatleast, performance is only improved for models with more than one Line object. However, for models with more than one Line performance is significantly improved. Batchprocessing,fatigueanalysisandOrcaFlexspreadsheetpost-processingtasksprocessjobsandloadcases concurrently, using all available processing resources. Thread count OrcaFlex manages a number ofexecution threads toperform theparallel calculations. Thenumber of these threads (thethreadcount)defaultstothenumberoflogicalprocessorsavailableonyourmachine,asreportedbythe operating system. This default will work well for most cases. Should you wish to change it you can use the Tools | Set Thread Count menu item. The thread count can also be controlled by a command line switch. w Introduction, Distributed OrcaFlex 15 1.4DISTRIBUTED ORCAFLEX DistributedOrcaFlexisasuiteofprogramsthatenablesacollectionof networked,OrcaFlexlicensedcomputersto runOrcaFlexjobs,transparently,usingspareprocessortime.FormoreinformationaboutDistributedOrcaFlex pleaserefertowww.orcina.com/Support/DistributedOrcaFlex.DistributedOrcaFlexcanbedownloadedfromthis address. OrcaFlex can also make use of machines with multiple processors using parallel processing technology. 1.5ORCINA LICENCE MONITOR The Orcina Licence Monitor(OLM) is a service that monitors the currentnumber of OrcaFlex licences claimed on a network in real time. Otherprograms that use theOrcaFlex programming interface (OrcFxAPI) such as Distributed OrcaFlex and the OrcaFlex spreadsheet are also monitored. You can obtain information on each licence claimed that includes: -Network information: the computer name, network address and the user name. -Licence information: the dongle name, the dongle type (network or local) and the time the licence was claimed. -Programinformation:whichmodulesarebeingused,theversion,andthelocationoftheprogramwhichhas claimedthelicence(usuallythisisOrcaFlex.exebutitcanbeExcel.exefortheOrcaFlexspreadsheetfor example). OLM can be downloaded from www.orcina.com/Support/OrcinaLicenceMonitor. 1.6DEMONSTRATION VERSION For an overview of OrcaFlex, see the Introduction topic and the tutorial. The demonstration version of OrcaFlex has some facilities disabled you cannot calculate statics or run simulation, and you cannot save files, print, export or copy to the clipboard. Otherwise the demonstration version is just like the full version, so it allows you to see exactly how the program works. InparticularthedemonstrationversionallowsyoutoopenanypreparedOrcaFlexdataorsimulationfile.Ifyou openasimulationfilethenyoucanthenexaminetheresults,seereplaysofthemotionetc.Therearenumerous examplefilesprovidedonthedemonstrationdisc.Theseexamplefilesarealsoavailablefrom www.orcina.com/SoftwareProducts/OrcaFlex/Examples. IfyouhavethefullversionofOrcaFlexthenyoucanusethedemonstrationversiontoshowyourcustomersyour OrcaFlexmodelsandresultsfortheirsystem.Todothis,givethemthedemonstrationversionandcopiesofyour OrcaFlexsimulationfiles.Thedemonstrationversioncanbedownloadedfrom www.orcina.com/SoftwareProducts/OrcaFlex/Demo. 1.7ORCAFLEX EXAMPLES OrcaFlex is supplied with an examples disc containing a comprehensive collection of examplefiles. These examples can also be found at www.orcina.com/SoftwareProducts/OrcaFlex/Examples. 1.8VALIDATION AND QA The OrcaFlex validation documents are available from www.orcina.com/SoftwareProducts/OrcaFlex/Validation. 1.9ORCINA Orcinaisacreativeengineeringsoftwareandconsultancycompanystaffedbymechanicalengineers,naval architects,mathematiciansandsoftwareengineerswithlongexperienceinsuchdemandingenvironmentsasthe offshore,marineandnuclearindustries.Aswellasdevelopingengineeringsoftware,weofferawiderangeof analysisanddesignserviceswithparticularstrengthindynamics,hydrodynamics,fluidmechanicsand mathematical modelling. Introduction, References and Links w 16 Contact Details Orcina Ltd. Daltongate Ulverston Cumbria LA12 7AJ UK Telephone: +44 (0) 1229 584742 Fax: +44 (0) 1229 587191 E-mail: orcina@orcina.com Web Site: www.orcina.com Orcina Agents We have agents in many parts of the world. For details please refer to www.orcina.com/ContactOrcina. 1.10REFERENCES AND LINKS References API,1993.APIRP2A-WSD,RecommendedPracticeforPlanning,DesigningandConstructingFixedOffshore Platforms Working Stress Design. American Petroleum Institute. API,2000.APIRP2A-WSD,RecommendedPracticeforPlanning,DesigningandConstructingFixedOffshore Platforms Working Stress Design. American Petroleum Institute. API,1998.APIRP2RD,DesignofRisersforFloatingProductionSystemsandTension-LegPlatforms.American Petroleum Institute. API,2005.APIRP 2SK,DesignandAnalysisof StationkeepingSystemsforFloatingStructures.AmericanPetroleum Institute. API. Comparison of Analyses of Marine Drilling Risers. API Bulletin. 2J. Aranha J A P, 1994. A formula for wave drift damping in the drift of a floating body. J. Fluid Mech. 275, 147-155. AubenyC,BiscontinGandZhangJ,2006.Seafloorinteractionwithsteelcatenaryrisers.OffshoreTechnology Research Center (Texas A&M University) Final Project Report (http://www.mms.gov/tarprojects/510.htm). Aubeny C, Gaudin C and Randolph M, 2008. Cyclic Tests of Model Pipe in Kaolin. OTC 19494, 2008. BarltropNDPandAdamsAJ,1991.Dynamicsoffixedmarinestructures.ButterworthHeinemannforMTD.3rd Edition. Batchelor G K, 1967. An introduction to fluid dynamics. Cambridge University Press. Bellanger M, 1989. Digital Processing of Signals. Wiley. Blevins R D, 2005. Forces on and Stability of a Cylinder in a Wake. J. OMAE, 127,39-45. Bridge C, Laver K, Clukey E,Evans T, 2004. Steel Catenary RiserTouchdown PointVertical Interaction Models.OTC 16628, 2004. Carter DJ T, 1982. Prediction of Wave height andPeriod for a Constant Wind Velocity Using the JONSWAP Results, Ocean Engineering, 9,no. 1, 17-33. Casarella M J and Parsons M, 1970. Cable Systems Under Hydrodynamic Loading.Marine Technology Society Journal 4, No. 4, 27-44. Chapman D A, 1984. Towed Cable Behaviour During Ship Turning Manoeuvres. Ocean Engineering. 11, No. 4. ChungJandHulbertGM,1993.Atimeintegrationalgorithmforstructuraldynamicswithimprovednumerical dissipation: The generalized- method. ASME Journal of Applied Mechanics. 60, 371-375. CMPT,1998.Floatingstructures:Aguidefordesignandanalysis.EditedbyBarltropNDP.CentreforMarineand Petroleum Technology publication 101/98, Oilfield Publications Limited. Coles S, 2001. An Introduction to Statistical Modelling of Extreme Values. Springer. Cummins W E, 1962. The impulse response function and ship motions. Schiffstechnik, 9, 101-109. w Introduction, References and Links 17 Dean R G, 1965. Stream function representation of non-linear ocean waves. J. Geophys. Res., 70, 4561-4572. Dirlik T, 1985. Application of computers in Fatigue Analysis. PhD Thesis University of Warwick. DNV-OS-F201, Dynamic Risers. DNV-RP-C205, Environmental Conditions and Environmental Loads. DNV-RP-H103, Modelling and Analysis of Marine Operations, April 2011. ESDU 71016. Fluid forces, pressures and moments on rectangular blocks. ESDU 71016 ESDU International, London. ESDU 80025. Mean forces, pressures and flow field velocities for circular cylindrical structures: Single cylinder with two-dimensional flow. ESDU 80025 ESDU International, London. FalcoM,FossatiFandRestaF,1999.Onthevortexinducedvibrationofsubmarinecables:Designoptimizationof wrapped cables for controlling vibrations. 3rd International Symposium on Cable Dynamics, Trondheim, Norway. Faltinsen O M, 1990. Sea loads on ships and offshore structures. Cambridge University Press. Fenton J D, 1979. A high-order cnoidal wave theory. J. Fluid Mech. 94, 129-161. FentonJD,1985.Afifth-orderStokestheoryforsteadywaves.J.Waterway,Port,Coastal&OceanEng.ASCE.111, 216-234. Fenton J D, 1990. Non-linear wave theories. Chapter in "The Sea Volume 9: Ocean Engineering Science", edited by B. Le MeHaute and D. M. Hanes. Wiley: New York.3-25. Fenton J D, 1995. Personal communication pre-print of chapter in forthcoming book on cnoidal wave theory. GregoryRWandPaidoussisMP,1996.Unstableoscillationoftubularcantileversconveyingfluid:Part1:Theory. Proc. R. Soc. 293 Series A, 512-527. Hartnup G C, Airey R G and Fraser J M, 1987. Model Basin Testing of Flexible Marine Risers. OMAE Houston. Hoerner S F 1965. Fluid Dynamic Drag, Published by the author at Hoerner Fluid Dynamics, NJ 08723, USA. Huse E, 1993. Interaction in Deep-Sea Riser Arrays. OTC 7237, 1993. IsherwoodRM,1987.ARevisedParameterisationoftheJONSWAPSpectrum.AppliedOceanResearch,9,No.1 (January), 47-50. IwanWD,1981.Thevortex-inducedoscillationof non-uniformstructuralsystems.JournalofSoundandVibration, 79, 291-301. Iwan W D and Blevins R D, 1974. A Model for Vortex Induced Oscillation of Structures.Journal of Applied Mechanics, September 1974, 581-586. Kotik J and Mangulis V, 1962. On the Kramers-Kronig relations for ship motions. Int. Shipbuilding Progress, 9, No. 97, 361-368. Lamb H, 1932. Hydrodynamics. 6th Edition.Cambridge University Press. LarsenCM,1991.FlexibleRiserAnalysisComparisonofResultsfromComputerPrograms.MarineStructures, Elsevier Applied Science. Longuet-HigginsMS,1983.Onthejointdistributionofwaveperiodsandamplitudesinarandomwavefield. Proceedings Royal Society London, Series A, Mathematical and Physical Sciences.389, 241-258. Maddox S J, 1998. Fatigue strength of welded structures. Woodhead Publishing Ltd, ISBN 1 85573 013 8. MalenicaSetal,1995.Waveandcurrentforcesonaverticalcylinderfreetosurgeandsway.AppliedOcean Research, 17, 79-90. MolinB,1994.Second-orderhydrodynamicsappliedtomooredstructures.Astate-of-the-artsurvey.Ship Technology Research. 41, 59-84. MorisonJR,O'BrienMD,JohnsonJW,andSchaafSA,1950.Theforceexertedbysurfacewavesonpiles.Petrol Trans AIME. 189. MuellerHF,1968.Hydrodynamicforcesandmomentsofstreamlinedbodiesofrevolutionatlargeincidence. Schiffstechnik. 15, 99-104. NewmanJN.1974.Second-order,slowly-varyingforcesonvesselsinirregularwaves.ProcIntSympDynamicsof Marine Vehicles and Structures in Waves, Ed. Bishop RED and Price WG, Mech Eng Publications Ltd, London. Introduction, References and Links w 18 Newman J N, 1977. Marine Hydrodynamics, MIT Press. NDP,1995.Regulationsrelatingtoloadbearingstructuresinthepetroleumactivities.NorwegianPetroleum Directorate. Ochi M K and Hubble E N, 1976. Six-parameter wave spectra, Proc 15th Coastal Engineering Conference, 301-328. Ochi M K, 1973. On Prediction of Extreme Values, J. Ship Research, 17, No. 1, 29-37. Ochi M K, 1998. Ocean Waves: The Stochastic Approach, Cambridge University Press. OilCompaniesInternationalMarineForum,1994.PredictionofWindandCurrentLoadsonVLCCs,2ndedition, Witherby & Co., London. PaidoussisMP,1970.Dynamicsof tubularcantileversconveyingfluid.J.Mechanical EngineeringScience,12,No2, 85-103. Paidoussis MP and Deksnis E B, 1970. Articulated models of cantilevers conveyingfluid: The study of a paradox.J. Mechanical Engineering Science, 12, No 4, 288-300. PaidoussisMPandLathierBE,1976.DynamicsofTimoshenkobeamsconveyingfluid.J.MechanicalEngineering Science, 18, No 4, 210-220. Palmer A C and Baldry J A S, 1974. Lateral buckling of axially constrained pipes.J. Petroleum Technology, Nov 1974, 1283-1284. PodeL,1951.TablesforComputingtheEquilibriumConfigurationofaFlexibleCableinaUniformStream.DTMB Report.687. PrinciplesofNavalArchitecture.Revisededition,editedbyJPComstock,1967.SocietyofNavalArchitectsand Marine Engineers, New York. Puech A, 1984. The Use of Anchors in Offshore Petroleum Operations. Editions Technique. RandolphMandQuigginP,2009.Non-linearhystereticseabedmodelforcatenarypipelinecontact.OMAEpaper 79259, 2009 (www.orcina.com/Resources/Papers/OMAE2009-79259.pdf). RawsonandTupper,1984.BasicShipTheory3rded,2:ShipDynamicsandDesign,482.LongmanScientific& Technical (Harlow). RieneckerMMandFentonJD,1981.AFourierapproximationmethodforsteadywaterwaves.J.FluidMech.104, 119-137. Roark R J, 1965. Formulas for Stress and Strain. 4th edition McGraw-Hill. Sarpkaya T, Shoaff R L, 1979. Inviscid Model of Two-Dimensional Vortex Shedding by a Circular Cylinder. Article No. 79-0281R, AIAA Journal,17, no. 11, 1193-1200. Sarpkaya T, Shoaff R L, 1979. A discrete-vortex analysis of flow about stationary and transversely oscillating circular cylinders. Report no. NPS-69SL79011, Naval Postgraduate School, Monterey, California. Rychlik I, 1987. A new definition of the rainflow cycle counting method. Int. J. Fatigue 9, No 2, 119-121. Skjelbreia L, Hendrickson J, 1961. Fifth order gravity wave theory. Proc. 7th Conf. Coastal Eng. 184-196. SobeyRJ,GoodwinP,ThiekeRJandWestbergRJ,1987.Wavetheories.J.Waterway,Port,Coastal&OceanEng. ASCE 113, 565-587. SparksCP,1980.Lecomportementmecaniquedesrisersinfluencedesprincipauxparametres.Revuedel'Institut Francais du Petrol, 35, no. 5, 811. SparksCP,1984.Theinfluenceoftension,pressureandweightonpipeandriserdeformationsandstresses.J. Energy Resources Technology, 106, Issue 1, 46-54. StandingRG,BrendlingWJ,WilsonD,1987.RecentDevelopmentsintheAnalysisofWaveDriftForces,Low-Frequency Damping and Response. OTC paper 5456, 1987. TanZ,QuigginP,SheldrakeT,2007.Timedomainsimulationofthe3Dbendinghysteresisbehaviourofan unbonded flexible riser. OMAE paper 29315, 2007 (www.orcina.com/Resources/Papers/OMAE2007-29315.pdf). Taylor R and Valent P, 1984. Design Guide for Drag Embedment Anchors,Naval Civil Engineering Laboratory (USA), TN No N-1688. w Introduction, References and Links 19 Torsethaugen K and Haver S, 2004. Simplified double peak spectral model for ocean waves, Paper No. 2004-JSC-193, ISOPE 2004 Touson, France. Thwaites, 1960. Incompressible Aerodynamics, Oxford, 399-401. Timoshenko S,1955. Vibration Problems in Engineering, van Nostrand. Triantafyllou M S, Yue D K P and Tein D Y S, 1994. Damping of moored floating structures.OTC 7489, Houston, 215-224. Tucker et al, 1984. Applied Ocean Research, 6, No 2. Tucker M J, 1991. Waves in Ocean Engineering. Ellis Horwood Ltd. (Chichester). WichersJEW,1979.Slowlyoscillatingmooringforcesinsinglepointmooringsystems.BOSS79(Second International Conference on Behaviour of Offshore Structures). Wichers J E W, 1988. A Simulation Model for a Single Point Moored Tanker. Delft University Thesis. WuM,Saint-MarcouxJ-F,BlevinsRD,QuigginPP,2008.PaperNo.ISOPE-2008-MWU10.ISOPEConference2008, Vancouver, Canada. (www.orcina.com/Resources/Papers/ISOPE2008-MWU-10.pdf) Young A D, 1989. Boundary Layers. BSP Professional Books, 87-91. Suppliers of frequency domain VIV software SHEAR7 AMOG Consulting Inc. 770 South Post Oak Lane, Suite 505 Houston, TX 77056 USA Attention: Dr. H. Marcollo Tel: +1 713 255 0020 Email: shear7@amogconsulting.com VIVA JD Marine 11777 Katy Freeway, Suite 434 South Houston, TX 77079 USA Tel: +1 281 531 0888 Email: info@jdmarineus.com w Tutorial, Getting Started 21 2TUTORIAL 2.1GETTING STARTED Thisshorttutorialgivesyouaveryquickrunthroughthemodelbuildingandresultspresentationfeaturesof OrcaFlex. On completion of the tutorial we suggest that you also look through the pre-run examples see Example Files. On starting up OrcaFlex, you are presented with a 3D view showing just a blue line representing the sea surface and a brown line representing the seabed. At the top of the screen aremenus, a tool bar and a status bar arranged in the mannercommontomostWindowssoftware.AsusualinWindowssoftware,nearlyallactionscanbedonein several ways: here, to avoid confusion, we will usually only refer to one way of doing the action we want, generally using the mouse. Figure:The OrcaFlex main window 2.2BUILDING A SIMPLE SYSTEM To start with, we will build a simple system consisting of one line and one vessel only. Using the mouse, click on the new vessel button on the toolbar. The cursor changes from the usual pointer to a crosshair cursor to show that you have now selected a new object and OrcaFlex is waiting for you to decide where to placeit.Placethecursoranywhereonthescreenandclickthemousebutton.A"ship"shapeappearsonscreen, positioned at the sea surface, and the cursor reverts to the pointer shape. To select the vessel, move the cursor close tothevesselandclickthemousebuttonthemessagebox(nearthetopofthe3Dview)willconfirmwhenthe vesselhasbeenselected.Nowpressandholddownthemousebuttonandmovethemousearound.Thevessel followsthemousehorizontally,butremainsattheseasurface.(Toaltervesselverticalposition,orotherdetails, select the vessel with the mouse, then double click to open the Vessel data window.) 2.3ADDING A LINE Nowaddaline.Usingthemouse,clickonthenewlinebutton.Thecrosshaircursorreappearsmovethe mouse to a point just to theright of the vessel and click. The line appears as a catenary loop at the mouse position. Movethemousetoapointclosetotheleft handendoftheline,pressandholddownthemousebuttonandmove the mouse around. The end of the line moves around following the mouse, and the line is redrawn at each position. Releasethemousebutton,movetotherighthandend,clickanddrag.Thistimetherighthandendofthelineis draggedaround.Inthisway,youcanputtheendsofthelinesroughlywhereyouwantthem.(Finalpositioningto exactlocationshastobedonebytypingintheappropriatenumbersselectthelinewiththemouseanddouble click to bring up the line data form.) Move the line ends until the left hand end of the line is close to the bow of the ship, the right hand end lies above the water and the line hangs down into the water. Tutorial, Adjusting the View w 22 At this point, the line has a default set of properties and both ends are at fixed positions relative to the Global origin. For the moment we will leave the line properties (length, mass, etc.) at their default values, but we will connect the left hand end to the ship. Do this as follows: 1.Click on the linenear the left hand end, to select thatend of the line;make sure you have selected the line, not the vessel or the sea. The message box at the left hand end of the status bar tells you what is currently selected. If you have selected the wrong thing, try again. (Note that you don't have to click at the end of the line in order to select it anywhere in the left hand half of the line will select the left hand end. As a rule, it is better to choose a point well away from any other object when selecting something with the mouse.) 2.Releasethemouseandmoveittothevessel,holddowntheCTRLkeyandclick.Themessageboxwillconfirm the connection and, to indicate the connection, the triangle at the end of the line will now be the same colour as the vessel. Nowselectthevesselagainanddragitaroundwiththemouse.Thelefthandendofthelinenowmoveswiththe vessel. Leave the vessel positioned roughly as before with the line in a slack catenary. 2.4ADJUSTING THE VIEW ThedefaultviewofthesystemisanelevationoftheglobalX-Zplaneyouarelookinghorizontallyalongthe positiveYaxis.Theviewdirection(thedirectionyouarelooking)isshownintheWindowTitlebarin azimuth/elevation form (azimuth=270; elevation=0). You can move your view point up, down, right or left, and you can zoom in or out, using the view control buttons near the top left corner of the window. Click on each of the top 3 buttons in turn: then click again with the SHIFT key held down. The SHIFT key reverses the action of the button. If you want to move the view centre without rotating, use the scroll bars at the bottom and right edges of the window. By judicious use of the buttons and scroll bars you should be able to find any view you like. Alternatively,youcanaltertheviewwiththemouse.HolddowntheALTkeyandleftmousebuttonanddrag.A rectangleonscreenshowstheareawhichwillbezoomedtofillthewindowwhenthemousebuttonisreleased. SHIFT+ALT+left mouse button zooms out the existing view shrinks to fit in the rectangle. Warning:OrcaFlexwillallowyoutolookupatthemodelfromunderneath,effectivelyfromunderthe seabed!Becausetheviewisisometricandalllinesarevisible,itisnotalwaysapparentthatthis has occurred. When this has happened, the elevation angle is shown as negative in the title bar.There are three shortcut keys which are particularly useful for controlling the view. For example CTRL+P gives a plan viewfromabove;CTRL+Egivesanelevation;CTRL+Qrotatestheviewthrough90abouttheverticalaxis.(CTRL+P and CTRL+E leave the view azimuth unchanged.) Now click the button on the 3D View to bring up the Edit View Parameters form. This gives a more precise way of controlling the view and is particularly useful if you want to arrange exactly the same view of 2 different models say 2 alternative configurations for a particular riser system. Edit the view parameters if you wish by positioning the cursor in the appropriate box and editing as required. Ifyoushouldaccidentallylosethemodelcompletelyfromview(perhapsbyzoomingintooclose,ormovingthe view centre too far) there are a number of ways of retrieving it: -Press CTRL+T or right click in the view window and select Reset to Default View. -Press the Reset button on the Edit View Parameters form. This also resets back to the default view. -Zoom out repeatedly until the model reappears. -Close the 3D View and add a new one (usethe Window|Add 3D View menu item). The new window will have the default view centre and view size. 2.5STATIC ANALYSIS Note:If you are running the demonstration version of OrcaFlex then this facility is not available. To run a static analysis of the system, click on the calculate statics button. The message box reports which line is beinganalysedandhowmanyiterationshaveoccurred.Whentheanalysisisfinished(almostinstantlyforthis simplesystem)theProgramStatemessageinthecentreoftheStatusBarchangestoread"StaticsComplete",and the Static Analysis button changes to light grey to indicate that this command is no longer available. The appearance ofthelinewillhavechangedalittle.Wheneditingthemodel,OrcaFlexusesaquickapproximationtoacatenary w Tutorial, Dynamic Analysis 23 shapeforgeneralguidanceonly,andthisshapeisreplacedwiththetruecatenaryshapewhenstaticanalysishas been carried out. (See Static Analysis for more details). WecannowexaminetheresultsofthestaticanalysisbyclickingontheResultsbutton.ThisopensaResults Selection window. You are offered the following choices: -Results in numerical and graphical form, with various further choices which determine what the table or graph will contain. -Results for all objects or one selected object. Ignorethegraphoptionsforthemoment,selectSummaryResultsandAllObjects,thenclickTable.Asummaryof thestaticanalysisresultsisthendisplayedinspreadsheetform.Resultsfordifferentobjectsarepresentedin differentsheets.Toviewmorestaticanalysisresultsrepeatthisprocess:clickontheResultsbuttonandselectas before. 2.6DYNAMIC ANALYSIS We are now ready to run the simulation. If you are running the demonstration version of OrcaFlex then you cannot do this, but instead you can load up the results of a pre-run simulation see Examples. ClicktheRunDynamicSimulationbutton.Asthesimulationprogresses,thestatusbarreportscurrent simulation time and expected (real) time to finish the analysis, and the 3D view shows the motions of the system as the wave passes through. ClicktheStartReplaybutton.Ananimatedreplayofthesimulationisshowninthe3Dviewwindow.Usethe viewcontrolkeysandmouseasbeforetochangetheview.ThedefaultReplayPeriodisWholeSimulation.This meansthatyouseethesimulationstartfromstillwater,thewavebuildingandwithitthemotionsofthesystem. Simulation time is shown in the Status bar, top left. Negative time means the wave is still building up from still water to full amplitude. At the end of the simulation the replay begins again. The replay consists of a series of "frames" at equal intervals of time. Just as you can "zoom" in and out in space for a closer view, so OrcaFlex lets you "zoom" in and out in time. Click on the Replay Parameters button, edit Interval to 0.5s and click OK. The animated replay is now much jerkier than before because fewer frames are being shown. Now click again on Replay Parameters, set Replay Period to Latest Wave and click on the Continuous box to deselect. The replay period shown is at the end of the simulationand has duration of a single wave period. At the end of the wave period the replay pauses, then begins again. NowclickontheReplayStepbuttontopausethereplay.Clickingrepeatedlyonthisbuttonstepsthroughthe replay one frame at a time a very useful facility forexamining a particular part of the motion in detail. Click with the SHIFT key held down to step backwards. You can then restart the animation by clicking on 'Start Replay' as before. To slow down or speed up the replay, click onReplayParametersandadjustthespeed.AlternativelyusetheshortcutsCTRL+FandSHIFT+CTRL+Ftomakethe replay faster or slower respectively. To exit from replay mode click on the Stop Replay button. 2.7MULTIPLE VIEWS YoucanaddanotherviewofthesystemifyouwishbyclickingontheViewbutton.Clickagaintoaddathird view, etc. Each view can be manipulated independently to give, say, simultaneous plan and elevation views. To make all views replay together, click on Replay Control and check the All Views box. To remove an unwanted view simply closeitsviewwindow.Torearrangethescreenandmakebestuseofthespace,clickWindowandchooseTile Vertical (F4) or Tile Horizontal (SHIFT+F4). Alternatively, you can minimise windows so that they appear as small iconsonthebackground,oryoucanre-sizethemormovethemaroundmanuallywiththemouse.Theseare standardWindowsoperationswhichmaybeusefulifyouwanttotidyupthescreenwithouthavingtoclosea window down completely. Tutorial, Looking at Results w 24 2.8LOOKING AT RESULTS Now click on the Results button. This opens a Results Selection window. You are offered the following choices: -Results as Tables or Graphs, with various further choices which determine what the table or graph will contain. -Results for all objects or one selected object. SelectTimeHistoryforanyline,thenselectEffectiveTensionatEndAandclicktheGraphbutton.Thegraph appearsinanewwindow.Youcancalluptimehistoriesof awiderangeof parametersformostobjects.Forlines, youcanalsocallupRangeGraphsofeffectivetension,curvature,bendmomentandmanyothervariables.These showmaximum,meanandminimumvaluesofthevariableplottedagainstpositionalongtheline.Detailed numerical results are available by selecting Summary Results, Full Results, Statistics and Linked Statistics. Time history andrange graph results are also available in numerical form select the variable you want andpress the Values button. The results can be exported as Excel compatiblespreadsheets for further processing as required. FurthernumericalresultsareavailableintabularformbyselectingSummaryResults,FullResults,Statisticsand Linked Statistics. Results Post-Processing Extra post-processing facilities are available through Excel spreadsheets. 2.9GETTING OUTPUT Youcangetprintedcopiesofdata,resultstables,systemviewsandresultsgraphsbymeansoftheFile | Print menu,orbyclickingPrintonthepop-upmenu.Outputcanalsobetransferredintoawordprocessororother application, either using copy and paste via the clipboard or else export/import via a file. Note:Printing and export facilities are not available in the demonstration version of OrcaFlex. 2.10INPUT DATA Take a look through the input data forms. Start by resetting the program: click on the Reset button. This returns OrcaFlextotheresetstate,inwhichyoucaneditthedatafreely.(Whileasimulationisactiveyoucanonlyedit certain non-critical items, such as the colours used for drawing.) Now click on the Model Browser button. This displays the data structure in tree form in the Model Browser. Selectanitemanddoubleclickwiththemousetobringupthedataform.Manyofthedataitemsareself explanatory.Fordetailsofadataitem,selecttheitemwiththemouseandpresstheF1key.Alternativelyusethe question mark Help icon in the top right corner of the form. Have a look around all the object data forms available to get an idea of the capabilities of OrcaFlex. End of Tutorial We hope you have found this tutorial useful. To familiarise yourself with OrcaFlex, try building and running models of a number of different systems. The manual also includes a range of examples which expand on particular points of interest or difficulty. Finally, please remember that we at Orcina are on call to handle your questions if you are stuck. w User Interface, Introduction 25 3USER INTERFACE 3.1INTRODUCTION 3.1.1Program Windows OrcaFlex is based upon a main window that contains theMenus, a Tool Bar, a Status Bar and usually at least one 3D view. The window caption shows the program version and the file name for the current model. Figure:The OrcaFlex main window Within this main window, any number of child windows can be placed which may be: 3D View Windowsshowing 3D pictorial views of the model Graph Windowsshowing results in graphical form Spreadsheet Windowsshowing results in numerical form Text Windowsreporting status Additional temporary windows are popped up, such as Data Forms for each object in the model (allowing data to be viewed and modified) and dialogue windows (used to specify details for program actions such as loading and saving files). While one of these temporary windows is present you can only work inside that window you must dismiss the temporary window before you can use other windows, the menus or toolbar. The actions that you can perform at any time depend on the current Model State. Arranging Windows 3DView,Graph,SpreadsheetandTextWindowsmaybetiledsothattheysitside-by-side,buttheymustremain within the bounds of the main window. The program rearranges the windows every time a new window is created. 3.1.2The Model OrcaFlexworksbybuildingamathematicalcomputermodelofyoursystem.Thismodelconsistsofanumberof objects that represent the parts of the system e.g. vessels, buoys, lines etc. Eachobjecthasaname,whichcanbeanylength.Objectnamesarenotcase-sensitive,soRiser,riserandRISER would all refer to the same object. This behaviour is the same as for Windows file names. The model always has two standard objects: -General contains general data, such as title, units etc. -Environment represents the sea, seabed, waves, current etc. You can then use the Model Browser or the toolbar to add other objects to represent the parts of your system. There is no limit, other than the capacity of your computer, to the number of objects you can add to the model. At any time, you can save your model to a data file. User Interface, Introduction w 26 3.1.3Model States OrcaFlexbuildsandanalysesamathematicalmodelofthesystembeinganalysed,themodelbeingbuiltupfroma series of interconnected objects, such as Lines, Vessels and Buoys. For more details see Modelling and Analysis. OrcaFlexworksonthemodelbymovingthroughasequenceof states,thecurrentstatebeingshownonthestatus bar. The following diagram shows the sequence of states used and the actions, results etc. available in each state. RESETCalculatingStaticsSimulatingSTATICS COMPLETESIMULATIONCOMPLETECalculateStaticPositionResetResetEdit orResetRunPauseRunSIMULATIONPAUSEDResetExtendSimulationSIMULATIONUNSTABLEReset Figure:Model States The states used are as follows: Reset The state inwhich OrcaFlex starts. In Reset state you can freely change the model andedit the data. Noresultsare available. Calculating Statics OrcaFlex is calculating the statics position of the model. You can abort the calculation by CLICKING the Reset button. Statics Complete The statics calculation is complete and the static position results are available. You are allowed to make changes to the model when in this state but if you make any changes (except for very minor changes like colours used) then the model will be automatically reset and the statics results will be lost. Simulating The dynamic simulation is running. The results of the simulation so far are available and you can examine the model data,butonlymakeminorchanges(e.g.coloursused).Youcannotstorethesimulationtoafilewhilesimulating you must pause the simulation first. w User Interface, Introduction 27 Simulation Paused Thereisasimulationactive,butitispaused.Theresultssofarareavailableandyoucanexaminethemodeldata. You can also store the part-run simulation to a file. Simulation Complete The simulation is complete. The simulation results are available and you can store the results to a simulation file for laterexamination.Youmustresetthemodel,byCLICKINGontheResetbutton,beforesignificantchangestothe model can be made. You can use the Extend Dynamic Simulation facility if you wish to simulate for a further period of time. Simulation Unstable Thesimulationhasbecomeunstable.Thesimulationresultsareavailableandyoucanstoretheresultstoa simulationfileforlaterexamination.Thisallowsyoutotryandunderstandwhythesimulationhasbecome unstable.Youmayalsowanttoexaminetheresultsupuntilthepointatwhichthesimulationbecameunstable. However,pleasetreattheseresultswithcautionbecausethesimulationeventuallywentunstablethisindicates that the dynamic simulation may not have converged at earlier simulation times. You must reset the model, by CLICKING on the Reset button, before significant changes to the model can be made. Typical model state flow To illustrate how model states work, here is an example of a typical working pattern: 1.In Reset state, open a new model from a data file or use the current model as the starting point for a new model. 2.In Reset state, add or remove objects and edit the model data as required for the new model. It is generally best touseaverysimplemodelintheearlystagesofdesignandonlyaddmorefeatureswhenthesimplemodelis satisfactory. 3.Runastaticanalysis(togettoStaticsCompletestate)andexaminethestaticpositionresults.Makeany correctionstothemodelthatareneededthiswillautomaticallyresetthemodel.Steps(2)and(3)are repeated as required. 4.Run a simulation and monitor the results during the simulation (in Simulating state). 5.IffurtherchangestothemodelareneededthenResetthemodelandeditthemodelaccordingly.Steps(2)to (5) are repeated as required. 6.Finalisethemodel,perhapsimprovingthediscretisation(forexamplebyreducingthetimestepsizesor increasingthenumberofsegmentsusedforLines).Runafinalcompletesimulation(toreach Simulation Complete state) and generate reports using the results. 3.1.4Toolbar Thetoolbarholdsavarietyofbuttonsthatprovidequickaccesstothemostfrequentlyusedmenuitems.The selection of buttons available varies with the current Program State. ButtonActionEquivalent Menu Item OpenFile | Open SaveFile | Save Model BrowserModel | Model Browser New VesselModel | New Vessel New LineModel | New Line New 6D BuoyModel | New 6D Buoy New 3D BuoyModel | New 3D Buoy New WinchModel | New Winch New LinkModel | New Link User Interface, Introduction w 28 ButtonActionEquivalent Menu Item New ShapeModel | New Shape Calculate StaticsCalculation | Single Statics Run SimulationCalculation | Run Dynamic Simulation Pause SimulationCalculation | Pause Dynamic Simulation ResetCalculation | Reset Start ReplayReplay | Start Replay Stop ReplayReplay | Stop Replay Step Replay ForwardsReplay | Step Replay Forwards Edit Replay ParametersReplay | Edit Replay Parameters Add New 3D ViewWindow | Add 3D View Examine ResultsResults | Select Results Help Contents and IndexHelp | OrcaFlex Help 3.1.5Status Bar The Status Bar is divided into three fields: The Message Box Thisisattheleft handend.Itshowsinformationabouttheprogressof thecurrentaction,suchasthenameof the currently selected object, or the current iteration number or simulation time. Error messages are also shown here. When a statics calculation is done messages showing the progress of the calculation are shown in the message box. ToseeallthemessagesfromthestaticscalculationCLICKonthemessageboxtheStatics Progress Windowwill then be opened. The Program State Indicator In the centre and shows which state the program is in (see Model States). The Information Box This is on the right. It shows additional information, including: -The global coordinates of the position of the cursor, in the current view plane. -Distances when using the measuring tape tool. 3.1.6Mouse and Keyboard Actions As well as the standard Windows mouse operations such as selection and dragging OrcaFlex uses some specialised actions.Clickingtherightmousebuttonovera3DView,GraphorTextWindowdisplaysapop-upmenuof frequentlyusedactions,suchasCopy,Paste,Exportetc.Forwireframe3DViewsandGraphWindowsthemouse can be used for zooming. Simply hold the ALT key down and using the left mouse button, drag a box over the region you want to view. All of the menu items can be selected from the keyboard by pressing ALT followed by the underlined letters. Example:To exit from the program (menu: File | Exit) press ALT+F then X, or ALT then F then X Anumberoffrequentlyusedmenuitemsmayalsobeaccessedbyshortcutkeys,suchasCTRL+Rtostartareplay. Seethetablesbelow.TheshortcutkeysarealsodisplayedontheOrcaFlexmenus.Wesuggestthatasyoubecome more familiar with the operation of OrcaFlex that you memorise some of the shortcut keys for actions that you use frequently. w User Interface, Introduction 29 Keys on Main Window New model CTRL+N Open file CTRL+O Save file CTRL+S Open data SHIFT+CTRL+O Save data SHIFT+CTRL+S Help F1 Print F7 Show / hide Model Browser F6 Switch to Model Browser SHIFT+F6 Calculate static position F9 Run dynamic simulation F10 Pause dynamic simulation F11 Reset F12 Open results selection form F5 Go to next window CTRL+F6 Go to previous window SHIFT+CTRL+F6 Tile windows vertically F4 Tile windows horizontally SHIFT+F4 Close selected window CTRL+F4 Close program ALT+F4 Keys on Model Browser View by Groups CTRL+ALT+G Edit data ENTER Move selected objects CTRL+M Rename object F2 Locate F3 Compare F8 Lock / Unlock objects CTRL+L Hide/Show CTRL+H Properties ALT+ENTER Cut CTRL+X Copy CTRL+C Paste CTRL+V Delete DELETE Switch to Main Window SHIFT+F6 Close browser F6 Keys on Data Forms Help F1 Go to next data form F6 Go to previous data form SHIFT+F6 Display batch script names for currently selected data item or table. F7 User Interface, Introduction w 30 Display Properties Report ALT+ENTER Show connections report F8 Copy form F9 Export form F10 Print form CTRL+P Open calculator F12 Data Selection Keys Go to next data item or table TAB Go to previous data item or table SHIFT+TAB Go to data item or table labelled with underlined letter ALT+LETTER Move around within a table Select multiple cells in tableSHIFT + SHIFT+HOME SHIFT+END Go to first or last column in table HOME END Go up or down table several rows at a time PGUP PGDN Data Editing Keys Enter new value for selected cellType new value Edit current value of selected cell F2 Open drop-down listALT + Move around within new data value being entered HOME END Accept edit ENTER Accept edit and go to adjacent cell in table Cancel edit ESC Copy selected cell(s) to clipboard CTRL+C Paste from clipboard CTRL+V Fill selection from top (copy top cell down) CTRL+D Fill selection from left (copy leftmost cell to right) CTRL+R Fill selection from bottom (copy bottom cell up) CTRL+U SHIFT+CTRL+D Fill selection from right (copy rightmost cell to left) CTRL+L SHIFT+CTRL+R Insert new rows in table INSERT Delete selected rows from table DELETE Graph Control Keys Use default ranges CTRL+T ZoomALT+drag, CTRL+wheel PanSHIFT+drag 3D View Control Keys Elevation view CTRL+E Plan view CTRL+P Rotate viewpoint up (increment view elevation angle)CTRL+ALT+ Rotate viewpoint down (decrement view elevation angle)CTRL+ALT+ Rotate viewpoint right (increment view azimuth angle)CTRL+ALT+ w User Interface, OrcaFlex Model Files 31 Rotate viewpoint left (decrement view azimuth angle)CTRL+ALT+ Rotate viewpoint +90 CTRL+Q Rotate viewpoint -90 SHIFT+CTRL+Q Zoom InCTRL+I, CTRL+wheel, ALT+drag Zoom OutSHIFT+CTRL+I, CTRL+wheel, SHIFT+ALT+drag Move view centre mouse panningSHIFT+drag Move view centre fine adjustment Move view centre coarse adjustmentCTRL + Edit view parameters for current 3D view CTRL+W Reset to default view CTRL+T Set as default view SHIFT+CTRL+T Show entire model CTRL+ALT+T 3D View Control Keys (for wire frame graphics only) Show / Hide local axes CTRL+Y Show / Hide node axes CTRL+ALT+Y Undo most recent drag CTRL+Z Lock/Unlock selected object CTRL+L Place new objectSPACE or ENTER Edit selected object CTRL+F2 Cut selected object to clipboard CTRL+X Copy selected object, or view if none selected, to clipboard CTRL+C Paste object from clipboard (followed by mouse click or ENTER to position the new object) CTRL+V Delete selected object DELETE Measuring tape toolSHIFT+CTRL+drag Replay Control Keys Start / Stop replay CTRL+R Replay faster CTRL+F Replay slower SHIFT+CTRL+F Step forwards one frame in the replay and pause CTRL+A Step backwards one frame in the replay and pause CTRL+B Edit replay parameters CTRL+D 3.2ORCAFLEX MODEL FILES 3.2.1Data Files OrcaFlex models are saved to either binary data files (.dat) or text data files (.yml). All versions of OrcaFlex can read binary data files. Text data files were only introduced in version 9.3a and so cannot be read by older versions of the program. Binary data files have strong version compatibility features. For example, when OrcaFlex attempts to open a binary datafilewrittenbyalaterversionoftheprogramitisabletoreportinformativecompatibilitywarnings.The programisnotabletobeashelpfulandinformativewhenworkingwithtextdatafilesacrossprogramversions. Whilst we strive to achieve as much compatibility as possible for text data files across program versions, we cannot achieve the same level of compatibility as that for binary data files. User Interface, OrcaFlex Model Files w 32 Textdatafiles,aswrittenbyOrcaFlex,containonlydatathatisactiveinthemodel.Forexample,ifimplicittime integrationisselectedinthemodelthenalldatarelatingtoexplicittimeintegrationisexcludedfromthetextdata file. On the other hand, binary data files contain all data whether or not it is active. The fact that the binary data file containsinactivedatacanbeveryusefulandso,ingeneral,wewouldrecommendthatmodelbuildingand development is performed using the binary data file. TextdatafilescanbecreatedwithouttheuseofOrcaFlexsimplybyenteringtextintoatexteditor.Ingeneralwe wouldnotadvocatethisapproachtomodelbuilding.Forverysimplesystemsitmaybeapracticalapproachbut morecomplexmodelsareusuallymucheasiertobuildandinspectusingthefullcapabilitiesandvisualisation strengths of OrcaFlex. On the other hand, text data files can be very effective when making minor changes to existing models. Using text data files for such minor variations of existing models makes it much easier to monitor just what has been changed, for example by using standard text differencing programs. Textdatafilesarehighlyreadableandself-documentingwhichmakesthemidealforQAandarchivalpurposes. Another application well suited to the use of text data files is automation. 3.2.2Text Data Files TextdatafilesareusedtodefineandrepresentOrcaFlexmodelsinahumanreadableandeasilyeditableformat. Text data files can be opened and saved by OrcaFlex. A very simple example is shown below: General: StageDuration: - 10.0 - 50.0 Lines: - Name: Line1 Length, TargetSegmentLength: - [60.0, 5.0] - [40.0, 2.0] - [120.0, 10.0] Thisexamplefirstdefinesa10sbuild-upstagefollowedbystage1with50sduration.ThenaLineiscreatedand named"Line1".Finallythesectiondataisspecified:threesectionsarecreatedwithvaryingsectionlengthsand segment lengths. Default values are used for all data which are not specified. Note:Theformatting(colour,bold,italicetc.)intheexamplesherehasbeenaddedtoaidreadability, and is not a feature or requirement of text data files themselves. YAML file format Text data files use a standard file format called YAML and should be saved with the .yml file extension. The YAML file format was chosen because it is extremely easy to read and write. YAML files are plain text files and so can be edited in any text editor. We have found Notepad++ to be a very effective editorforYAMLfiles.Notepad++hasatabbedinterfaceforeasyeditingofmultiplefilesandhascodefoldingand syntax highlighting facilities that work well with YAML files. Note:YAML files must be saved with the UTF-8 character encoding. More details on the YAML format and Notepad++ can be obtained from the following web sites: -http://en.wikipedia.org/wiki/YAML YAML page on Wikipedia. -http://www.yaml.org/ Official YAML homepage. -http://www.yaml.org/spec/ Complete technical specification of YAML. -http://notepad-plus.sourceforge.net/ Notepad++. Elements of a text data file The most basic element of a text data file is the name/value pair: UnitsSystem: SI Thename(UnitsSystem)iswrittenfirst,followedbyacolon(:),thenaSPACE,andthenthevalue(SI).Thenames used in text data files are the same as used to identify data items in batch script files. Names and values in YAML files can contain spaces and other punctuation: w User Interface, OrcaFlex Model Files 33 General: StaticsMethod: Whole System statics Lines: - Name: 12" Riser - Name: Umbilical, upper - Name: "!$%^&*(){}[]=+-_#~'@:;/?.>,0, E(z) is replaced by E(0) + z.E'(0), where E' is the rate of change of E with z. Wave Spectra ISSC spectrum The ISSC spectrum (also known as Bretschneider or modified Pierson-Moskowitz) is defined as: S(f) = 5/16 Hs2 fm4 f -5 exp(-5/4 [f/fm] -4) wheref isfrequency.Theothertwoparameters,thepeakfrequencyfmandthesignificantwaveheightHsaredata items. For more details see Tucker 1991, page 107. JONSWAP spectrum The JONSWAP spectrum is defined as: S(f) = (g2/164) f -5 exp(-5/4 [f/fm] -4) b wheregisthegravitationalconstant,b=exp(--2[f/fm-1]2),=1forffm,=2forf>fmandtheother parameters , , 1 and 2 are data items. For more details see: -Barltrop and Adams, page 277. -Tucker 1991, page 108. -Isherwood 1987. Ochi-Hubble spectrum See the Ochi-Hubble paper for details of the spectral formula. The Ochi-Hubble Spectrum allows two peaked spectra to be set up, enabling you to represent sea states that include both a remotely generated swell and a local wind generated sea. Example of Ochi-Hubble Spectrum01234560 1 2 3 4Relative Frequency rS(r) [m^2] The Ochi-Hubble wave spectrum is the sum of two separate component spectra the example graph shows the two componentsandtheirsum.Thecomponentspectrumwiththelowerfrequencypeakcorrespondstotheremotely generatedswellandtheonewiththehigherfrequencypeakcorrespondstothelocalwindgeneratedsea.Thisis whytheOchi-Hubblespectrumisoftencalledatwo-peakedspectrum;howeverinpractice,theresultingtotal spectrumtypicallyhasonly onepeak(fromtheremotelygeneratedswell)plusashoulderofenergyfromthelocal wind generated sea. Theory, Environment Theory w 154 ThetwocomponentspectraareeachspecifiedbyasetofthreeparametersHs1,fm1,1forthelowerfrequency component and Hs2, fm2, 2 for the higher frequency component. See Data for Ochi-Hubble Spectrum. In OrcaFlex you can either specify all these 6 parameters explicitly, or you can simply specify the overall significant wave height Hs and tell OrcaFlex to automatically select the most probable 6 parameters for that value of Hs. In the latter case, OrcaFlex uses 'most probable' parameters based on formulae given in the Ochi-Hubble paper (table 2b). Torsethaugen spectrum TheTorsethaugenspectrumisanothertwo-peakedspectrum,moresuitedtoNorthSeaapplicationthanOchi-Hubble. See the Torsethaugen and Haver paper for details of the spectral formula. Warning:Thetwo-peakedOchi-HubbleandTorsethaugenspectramakenoallowanceforthedirectionality oftheswellandwindcomponentsoftheseastate.Inrealitytheseparatecomponentsfrequently comefromdifferentdirections.However,anOrcaFlexwavetrainhasasingleprincipaldirection. Because of this it is more appropriate to model a two-peaked sea state using two separate OrcaFlex wave trains, one for the swell component and one for the local wind generated component. Gaussian Swell spectrum The Gaussian Swell spectrum is based on the normal (or Gaussian) probability density function and is defined as: S(f) = (Hs/4)2-1(2)- exp(-[f-fm]2/22) where Hs, fm and are the input data. Non-linear Wave Theories OrcaFlex models two types of waves, periodic regular waves and random waves. Aregular wave is a periodic wave with a single period. A random wave in OrcaFlex is a superposition of a number of regular linear waves of differing heights and periods. We shall not discuss random waves here. Forverysmallwavesindeepwater,Airywavetheory(alsoknowaslinearwavetheory)isvalid.Manywavesin practicalengineeringusedonotfallintothiscategory,hencetheneedfornon-linearwavetheories.Theseinclude Stokes'5thordertheory,Dean'sstreamfunctiontheoryandFenton'scnoidaltheorywhichareallavailablein OrcaFlex. We shall give an outline of these theories here in the form of concise abbreviations of the relevant papers. For an overview of all the theories considered here see Sobey R J, Goodwin P, Thieke R J and Westberg R J, 1987. Tofixnotationweusethefollowingconventionsthroughout.Theseconventionsaredifferentfromthoseusedin OrcaFlexbutweusethemhereinordertoagreewiththeliterature.Weassumethatthewaveislong-crestedand travels in the x direction and we shall work only in the (x,z) plane. The seabed has z = 0 and the mean water level is given by z = d, where d is the water depth (at the seabed origin). The wave is specified by wave height (H) and wave period(T)andthewavelength(L)willbederived.Thehorizontalandverticalparticlevelocitiesaredenotedbyu andvrespectively.Weassumeamovingframeofreferencewithrespecttowhichthemotionissteadyandx = 0 under a crest. See Stokes' 5th, Dean's stream function theory and Fenton's cnoidal theory for a brief overview of each of the non-linearwavetheoriesavailableinOrcaFlexandforguidanceonhowtodecideonwhichwavetheorytousein practice. Dean Stream Function theory Atypicalapproachtowavetheorymakesuseoftheideaof avelocitypotential.Thisisavectorfield(x,z)whose partial derivatives are the particle velocities of the fluid. That is: /x = u and /z = v. Chappeleardevisedawavetheorybasedonfindingthebestfitvelocitypotentialtothedefiningwaveequations. This was quite complicated and Dean's idea was to apply the same idea to a stream function. A stream function is a vector field (x,z) which satisfies /x = -v and /z = u. Dean'soriginalpaperDean(1965)wasintendedtobeusedtofitstreamfunctionstowaveswhoseprofilewas alreadyknown,forexampleawaverecordedinawavetank.ForthepurposeofOrcaFlextheuserprovides information on the wave train in the form of water depth, wave height and wave period and we wish to find a wave theorywhichfitsthisdata.ThusDean'stheoryinitsoriginalformdoesnotapplyandwechoosetofollowthe w Theory, Environment Theory 155 stream function theory of Rienecker and Fenton (1981). This method is also known as Fourier approximation wave theory. The problem is to find a stream function which: 1.satisfies Laplace's equation 2/x2 + 2/z2 = 0, which means that the flow is irrotational, 2.is zero at the seabed, that is (x,0) = 0, 3.is constant at the free surface z = (x), say (x,) = -Q and 4.satisfies Bernoulli's equation [ (/x)2 + (/z)2 ] + = R, where R is a constant. In these equations all variables have been non-dimensionalised with respect to water depth d and gravity g. By standard methods, equations (1) and (2) are satisfied by a stream function of the form (x,z) = B0 z + Bj [sinh (jkz) / cosh (jk)] cos (jkx) where k is the wave number which is as yet undetermined, and the summation is from j = 1 to N. The constant N is said to be the order of the stream function. The problem now is to find coefficients Bj and k which satisfy equations (3) and (4). Implementing stream function theory requires numerical solution of complexnon-linear equations. The number of these equations increases as N increases and there is a short pause in the program while these equations are solved. Formostwavesthedefaultvaluewillsuffice.However,fornearlybreakingwavesthesolutionmethodsometimes has problems converging. If this is the case then it might be worth experimenting with different values. Accuracy of method Because the method is a numerical best fit method it does not suffer from the truncation problems of theStokes' 5th andcnoidaltheories.Forthesemethods,powerseriesexpansionsareobtainedandthentruncatedatanarbitrary point. If the terms which are being ignored are not small then these methods will give inaccurate answers. In theory, Dean'smethodshouldcopewellinsimilarcircumstancesasitisfindingabestfittothegoverningequations.This meansthatstreamfunctionwavetheoryisveryrobust.InveryshallowwaterFentonbelievesthathishighorder cnoidal wave theory is best, although we would recommend stream function theory here. It is possible that, by their verynature,Stokes'5thandthecnoidaltheoriesmaygiveinaccurateresultsifappliedtothewrongwaves.Inall circumstances the stream function method, if it converges, will give sensible results. Hence it can be used as a coarse check on the applicability of other theories. That is if your preferred wave theory gives significantly different results from Dean's, applied to the same wave, then it is probably wrong! Stokes' 5th Theengineeringindustry'sstandardreferenceon5thorderStokes'wavetheoryisSkjelbreiaandHendrickson (1961).Thispaperpresentsa5thorderStokes'theorywithexpansiontermakwhereaistheamplitudeofthe fundamental harmonic and k = 2 / L is the wave number. The length a has no physical meaning and by choosing ak asexpansionparameter,convergenceforverysteepwavescannotbeachieved.Fenton(1985)givesa5thorder Stokes' theory based around an expansion term kH/2 and demonstrates that it is more accurate than Skjelbreia and Hendrickson's theory. Thus it is Fenton's theory which is implemented in OrcaFlex. It is worthnoting that the linear theory of Airy is a 1st order Stokes' theory. Assuming that the user supplies wave train information comprising water depth, wave height and wave period then thewavenumberkmustbecomputedbeforethetheorycanbeapplied.Inordertodothisanon-linearimplicit equation in terms of k is solved using Newton's method. This equation is known as the dispersion relationship. Once k is known, a number of coefficients are calculated and these are used for power series expansions in order to find the surface profile and wave kinematics. Accuracy of method Inherent in the method is a truncation of all terms of order greater than 5. Thus if the terms which are discarded are significantthenthistheorywillgivepoorresults.SeeRangesofapplicabilityforthewavesforwhichStokes'5th theory is valid, but essentially this is a deep water, steep wave theory. Cnoidal theory Thisisasteadyperiodicwaterwavetheorydesignedtobeusedforlongwavesinshallowwater.TheStokes'5th order theory is invalid in such water as the expansion term is large and the abandoned terms due to truncation are significant.Thehigh-ordercnoidaltheoryofFenton(1979)hasbeenregardedasthestandardreferenceformany Theory, Environment Theory w 156 yearsbutitgivesunsatisfactorypredictionsofwaterparticlevelocities.ThisworkhasbeensupersededbyFenton (1990 and 1995). Fenton'soriginalpapergaveformulaeforfluidvelocitiesbasedonaFourierseriesexpansionabouttheterm = H / d.InhislaterworksFentondiscoveredthatmuchbetterresultscouldbeobtainedbyexpandingabouta "shallowness" parameter . We follow this approach. A 5th order stream function representation is used but instead of termsinvolving cos the Jacobianelliptic function cn is used, hence the term cnoidal. The function takes two parameters, x as usual, and also m which determines how cuspedthefunctionis.Infactwhenm = 0,cnisjustcosandtheJacobianellipticfunctionscanberegardedasthe standard trigonometric functions. The solitary wave which has infinite length corresponds to m = 1 and long waves in shallow water have values of m close to 1. Fenton shows that the cnoidal theoryshould onlybe applied for long waves in shallow water and for such waves m is close to 1. The initial step of the solution is to determine m and an implicit equation with m buried deep within must be solved. AsintheStokes'theorythisequationisthedispersionrelationship.Thesolutionisperformedusingthebisection method since the equation shows singular behaviour for m 1 and derivative methods fail. AftermhasbeendeterminedFentongivesformulaetocalculatesurfaceelevationandotherwavekinematics.In practicemiscloseto1andFentontakesadvantageofthistosimplifytheformulae.Hesimplysetsm = 1inall formulaeexceptwheremistheargumentofanellipticorJacobianfunction.ThistechniqueisknownasIwagaki approximation and proves to be very accurate. Ranges of Applicability RegularwavetrainsarespecifiedinOrcaFlexbywaterdepth,waveheightandwaveperiod.Whichwavetheory should one use for any given wave train? For an infinitesimal wave in deep water then Airy wavetheory is accurate. For finite waves a non-linear theory should be used. In order to decide which wave theory to use one must calculate the Ursell number given by U = HL2 / d 3 See Non-linear Wave Theories for notation conventions used. IfU < 40thenthewavesaresaid tobeshortandStokes'5thmaybeused.ForU > 40wehavelongwavesandthe cnoidal wavetheory canbeused. Thestream function theory is applicablefor anywave.Theboundarynumber 40 should not be considered a hard and fast rule. In fact for Ursell number close to 40 both the Stokes' 5th theory and thecnoidaltheoryhaveinaccuraciesandthestreamfunctionmethodisrecommended.Inregionswellawayfrom Ursell number 40 then the relevant analytic theories (Stokes' 5th or cnoidal) perform very well. Our recommendations are: Ursell numberRecommended wave theory 0 -90 if cos()0 -90 if sin()0 -90 if sin()0 +90 if cos()0 0 if sin(2) fm2. For swell dominated sea states, fm2 = fm and fm1 < fm2. Warning:TheTorsethaugenspectrummakesnoallowanceforthedirectionalityoftheswellandwind componentsoftheseastate.Inrealitytheseparatecomponentsfrequentlycomefromdifferent directions.However,anOrcaFlexwavetrainhasasingleprincipaldirection.Becauseofthisitis often more appropriate to model a two-peaked sea state using two separate OrcaFlexwave trains, one for the swell component and one for the local wind generated component. 6.5.10Data for Gaussian Swell Spectrum The Gaussian Swell spectrum is typically used to model long period swell seas. Hs, fm, Tp and The Gaussian Swell spectrum is specified by Hs, fm and . The fm and Tp data items are linked by the relationship fm = 1/Tp. If you enter one the other will be updated according to this equality. 6.5.11Data for User Defined Spectrum A user defined spectrum is specified by giving a table of values of S(f), where S(f) is the spectral energy as a function of frequency f. The values of f specified do not need to be equally spaced. For intermediate values of f (i.e. between those specified inthetable)OrcaFlexuseslinearinterpolationtoobtainthespectralordinateS(f).Andforvaluesoffoutsidethe range specified in the table OrcaFlex assumes that S(f) is zero. Your tableshould therefore include enough points to adequately define the shape you want (important where S(f) is large or has high curvature) and should cover the full range over which the spectrum has significant energy. OrcaFlexreportsonthedataformHsandTzthatcorrespondtothespectrumspecified.Thesearecalculatedusing the standard formulae: Hs = 4m0. Tz = (m0/m2). System Modelling: Data and Results, Environment w 236 where m0 and m2 are the zeroth and second spectral moments. 6.5.12Data for Time History Waves A time history wave train is defined by a separate text file that contains the wave elevation as a function of time. To use this you need to do the following: -Create a suitabletime history text filedefining the wave elevation as a function of time. The time values inthe filemustbeequallyspacedandinseconds.TheelevationvaluesmustbetheelevationatthespecifiedWave Origin,measuredpositiveupwardsfromthestillwaterlevelspecifiedintheOrcaFlexmodel,andusingthe same units as those in the OrcaFlex model. -Setup the time history data as described in Data in Time History Files. -SettheWaveTimeOrigintopositiontherequiredsectionofwavetimehistorywithinthesimulationperiod. You can use the View Profile button (on the Waves Preview page on the environment data form) to see the wave elevation as a function of simulation time. -Set the Minimum Number of Components. This affects the number of Fourier components that will be used to modelthetimehistorywave.Itshouldbesethighenoughtogivedesiredaccuracy,butnotethatusingavery large number of components may significantly slow the simulation. More details are given below. How Wave Time History Data is Used Briefly, OrcaFlex uses a Fast Fourier Transform (FFT) to transform the data into a number of frequency components. Each component is then used to define a single Airy wave and these Airy waves are then combined to give the wave elevation and kinematics at all points. TheView Wave Components and View Spectrum buttons on the data form show (in tabular and power spectral density graph form respectively) the Airy wave components that OrcaFlex will use to model the waves. Note that the FFT requires the number of samples it uses from the time history file, N say, to be a power of 2, and it producesN/2components.Becauseofthis,thetimehistoryfilemustcontainasequenceofNsamplesthatcovers theperiodofthesimulation,whereNisapowerof2thatisatleasttwicethespecifiedminimumnumberof components. Warning:If thetimehistoryfiledoesnotcontainenoughsamplestoachievethis,thenzero-paddingwillbe usedtoextendthetimehistoryuntilitdoes.Thisislikelytointroducespurioushighfrequencies into the waves, so we recommend that this is avoided by providing more actual samples. Here are more details. 1. OrcaFlex first selects the elevation values that cover the simulation period TodothisOrcaFlexsearchesthetimehistoryfileandselectsthetimesamplesthatcoverthesimulationperiod. These will be the time samples from time (T0 - BuildUpDuration) to (T0 + SimulationDuration) where BuildUpDuration is the length of the build-up stage of the simulation, SimulationDuration is the length of the remainingstagesandT0=SimulationTimeOrigin-WaveTimeOrigin.Thesetimeoriginsettingsallowyou,ifyou want, to shift the simulation relative to the time history. 2. OrcaFlex then includes more samples, if necessary Letnbethenumberofsamplesselectedinstep1.Inordertoachievethespecifiedminimumnumberof components, m say, OrcaFlex needs at least 2m samples. So if n is less than 2m then OrcaFlex selects more samples from the file (taken equally from earlier and later in the file, if possible) until it has 2m samples. If OrcaFlex runs out of samples in the file while doing this then an error message is given; you must then either provide more samples in the time history file or else reduce the minimum number of components requested. HoweverOrcaFlexalsoneedsthenumberof samplestobeapowerof 2,sincethatisneededinordertouseafast Fourier transform. So if 2m is not a power of 2 then OrcaFlex again selects more samples from the file (taken equally fromearlierandlaterinthefile,ifpossible)untilthenumberof selectedsamplesisapowerof2.IfOrcaFlexruns outofsamplesinthefilewhiledoingthisthenitzero-pads(i.e.itaddsextrasamplesofvaluezero);youwillbe warned if this happens. w System Modelling: Data and Results, Environment 237 3. OrcaFlex uses a fast Fourier transform to obtain Fourier components Theselectedtimehistorysamples,Nofthemsay,areconvertedintofrequencydomainformusingaFast FourierTransform(FFT).ThisgivesN/2sinusoidalFouriercomponents.TheViewWaveComponentsbutton reports their numerical values and the View Spectrum shows their spectrum. 4. OrcaFlex models the time history wave as the superposition of Airy waves N/2Airywavesarecreated,withperiods,amplitudesandphasesthatmatchtheFouriercomponents.Thetime history wave is then modelled as the superposition of these Airy waves. Warning:ThislaststepeffectivelyusesAirywavetheorytoextrapolatefromtheWaveOrigin,wherethe surfaceelevationhasbeendefined,toderivesurfaceelevationatotherpointsandtoderivefluid kinematicsfromthesurfaceelevationreadings.Thisextrapolationintroduceserrors,which become worse the further you go from the Wave Origin. It is therefore recommended that the Wave Origin (= the point the timehistoryfiledata applies to)is placedclose to themainwave-sensitive parts of the model. 6.5.13Data for User Specified Components TheUserSpecifiedComponentswavetypeallowsyoutospecifythewavetrainasthesumofanumberof sinusoidal components. For each component you specify: Frequency or Period YoumayspecifyeitheroftheseandtheotherisautomaticallyupdatedusingtherelationshipPeriod=1/ Frequency. Amplitude The single amplitude of the component that is half the peak to trough height. Phase lag The phase lag relative to the wave train time origin. 6.5.14Data for Response Calculation Hs ThesignificantwaveheightofthetruncatedwhitenoisespectrumusedfortheSpectralResponseAnalysis.A truncated white noise spectrum has energy spread evenly over the a specified range of frequencies. ThetotalenergyofthespectrumisdeterminedbyHsusingthestandardformulam0=(Hs/4)2wherem0isthe zeroth spectral moment, that is the total spectral energy. OrcaFlex also reports Tz = (m0/m2). A more detailed discussion of the issues involved in choosing Hs is given in Load Cases Data for Spectral Analysis. Target Frequency Range ThesedataitemsdeterminethefrequencyrangeofthetruncatedwhitenoisespectrumusedfortheSpectral Response Analysis. ThewavecomponentsthatOrcaFlexusestorepresentthisspectrumarecarefullychosen.Theyareselectedto matchthefrequenciesproducedbytheFastFourierTransform(FFT)usedtocalculatethespectralresponse.This process is described in more detail in the Spectral Response Analysis theory section. It is possible for the range of FFT frequencies not to cover the Target Frequency Range. If this happens then as much of the target range is used as is possible. You will be warned if the actual frequency range cannot achieve the Target Frequency Range. 6.5.15Waves Preview When using a random wave or a time history wave, OrcaFlex providestwopreview facilities to aid selection of the wave, namely List Events and View Profile. These are provided on the Waves Preview page on the environment data form and are documented below. Notes:Thesecommandsworkintermsofglobaltime,ratherthansimulationtime.Thisenablesyouto search through a period of global time looking for an interesting wave event and then set thetime origins so that the simulation covers that event. System Modelling: Data and Results, Environment w 238 If you are using multiple wave trains then these commands report the combined sea state from all of the wave trains. See also Setting up a Random Sea. Position This is the point towhich theList Events,View Profile and Horizontal Velocity commands apply. Since wave trains varyinspaceaswellastimeyoushouldnormallysetthispointtobeclosetoasystempointofinterest,suchasa riser top end position. View Profile This plots a time history of wave elevation at the specified Position over the specified interval of global time. An example of the use of these commands is to useList Events to scan over a long period of global time (e.g. 10000 seconds or more), look for large waves and then use View Profile to look in more detail at short sections of interest. Havingdecidedwhichpartofthewavetraintouse,thesimulationtimeorigincanthenbesettojustbeforethe period of interest, so that the simulation covers that