World Applied Sciences Journal 32 (4): 577-581, 2014ISSN 1818-4952 IDOSI Publications, 2014DOI: 10.5829/idosi.wasj.2014.32.04.107Corresponding Author: Gunawan, M. Baqi, Department of Mechanical Engineering, University of Indonesia, Jakarta 16424, Indonesia. 577The Effect of Ribblet Structure on Resistance in Fast Speed Ship ModelGunawan M. Baqi, M.A. Talahatu and YanuarDepartment of Mechanical Engineering, University of Indonesia, Jakarta 16424, IndonesiaAbstract: Energy efficiency is the major interesting topic to be studied for many years. In sea transportation,reductionoffuelconsumptionbecomeimportanttoincreaseprofit.Reductionresistanceofshipisclosedrelated to fuel consumption demand. Reducing resistance to fluid flow can be obtained by providing specialroughness (ribblet), polymer additives, coating, surfactants and fiber on the surface of the ships hull. Fish skinsurfacelikesharkfishisgeneratedbyspecialroughness.Thisphenomenaisonemethodtoreductioninfrictionalresistanceofship.Thepurposeofthisresearchistoidentifytheeffectofcoatingribbletformtoestimationondragreductionintheresistanceofhighspeedshipmodel.Thisresearchcarriedoutexperimentally using towing tank test. The ship model is Indonesian fast patrol boat (FPB-57) with main-hullL = 2.45 m, B = 0.40 m and T = 0.19 m is pulled by an electric motor which speed can be varied and adjusted. Theship model resistance was precisely measured by a load celltransducer.The ribblet form is varried by threeform: blade form, scalloped form and sawtooth. Comparison of ship model resistance with 3 different ribblet formis shown on the graph as a function of the total resistance coefficient and Froude number. It was found out thatthe ship model with coating ribblet could have less resistance compared to mono-hull of similar displacement.The results shows the drag reduction about 10 % at Fr 0.55 for blade ribblet form. Key words: Specialroughness(ribblet) Totalresistancecoefficient FastpatrolboatFPB57 EnergyefficiencyFroudes numberINTRODUCTION biopolymer to be one method to reduce drag phenomenaResearch about drag reduction in many aspects is polysaccharides produced by living organisms cancontinue done for increase of human purposes in the provide effective drag reduction. Polysaccharides ofpresent. Dragreduction of civil transport ship not only several fresh water and marine algae, fish slimes, seawaterdirectly concerns performance, but also indirectly, of slime and other fresh water biological growths have beencourse, cost and environment. Fuel consumption found to be good drag reducers [2]. Hoyt and W. Whiterepresents about 20% of the direct operating cost which [2] have tested the effect of adding hagfish slime andis of utmost importance for the shipping line, for a typical reduced drag reduction until 14.5%. Ripken and Pilch [3]long range transport of ship. Drag reduction directly reported that slime dogfish was able to reduce the flowimpacts on the direct operating cost. Ship resistance resistance. Rosen and Neri [4] also have examined areduction due to fuel consumption tobe concerned study. variety of slime produced by several species of river andThe water animals like fish is naturally secret mucus sea fish. From the study concluded that a reduction in thethat is generated thick layer layer. The mucus secreted by flow resistance. Tests were conducted with a rheometer.fish causes a reduction in drag as they move through Yanuar et al. [5], experimentally the drag reductionwater and also protects the fish fromabrasion, by making effects due to the introduction of slime solution into athe fish slide across objects rather than scrape and catamaran ship model at the basin. The test results showdisease, by making the surface of the fish difficult for that an effective drag reduction of up to 7% at Fr = 0.45microscopic organisms to adhere [1]. Additive solution eg can be achieved. Yanuar et al. [6] also investigated dragin ship. Biopolymers, for example: high molecular weightWorld Appl. Sci. J., 32 (4): 577-581, 2014578Fig. 1: Experimental set-upreduction on Indonesia navy fast patrol boat (FPB) 57 mtype model with the following main dimensions: L=2450mm, B=400 mmand T=190 mmusing micro bubble. It wasshown that micro bubble injection behind the mid-ship isthe best location to achieve the most effective drag Fig. 2: Positioning of Ribbletreduction and the drag reduction caused by the micro-bubbles can reach 6%-9%.The compliant skin of the dolphin has also beenstudiedfordrag-reducingproperties.Byrespondingtothepressurefluctuationsacrossthesurface,acompliantmaterialonthesurfaceofanobjectinafluidflowhasbeen showntobebeneficial.Thoughearlystudiesshowed dramaticdragreductionbenefits,laterstudieshave only been able to confirm 7 per cent drag reduction[7]. Brian Dean and Bharat Bhushan [8] have studied morecomplex about shark skin drag reduction. They found thatshark skin is develope more and more ribblet form. Theyalso investigate some mechanism drag reduction of ribbletform. Figure 3. Variation of Ribblet FormThe purpose of this research is to identify the effectof coating ribblet form to estimation on drag reduction in motor and AC voltage regulator. Ship model pulled by anthe resistanceofhighspeedshipmodel.Thisresearch electric motor and the motor rotation can be used to pullcarriedoutexperimentallyusingtowingtanktest.The the ship model with a constant speed. The comparison ofshipmodelisIndonesianfastpatrolboat(FPB-57)with thetotalresistancebetweenshipmodelswithoutribbletmain-hull L = 2.45 m, B = 0.40 m and T = 0.19 m is pulled and with ribblet placed is analyzed. Total resistance wasby anelectricmotorwhichspeedcanbevariedand measuredbyusingaloadcelltransducerforeachrunadjusted.Theshipmodelresistancewasprecisely overthetestrangeofFroudenumbers.Theloadcellmeasuredbyaloadcelltransducer.Theribbletformis transducerwasconnectedtotheshipmodelatapointvarried bythreeform:bladeform,scallopedformand locatedamidshipsandverticallyabovethebaseline,sawtooth.Comparisonofshipmodelresistancewith 3 allowingthemodeltomovefreelyintheverticalplane.different ribblet form is shown on the graph as a function Testingisdonebyrecordingtheresultsofthestringof the total resistance coefficient and Froude number. tensionontheloadcellthroughthedataacquitisionareExperimental Set-Up: Figure 1 shows the experimental Figure2showsthepositionsofribbletonshipsset-up in the basin. The basin dimension of basin is 50 m main-hull. Ribblet is placed on the stem of ship hull. Thereof length, 20 m of width of 20 and 2 m of water depth. This isthree variation of ratio area between ribblet with totalexperimentalset-upconsistsofloadcelltransducer, wetted surface area of ship model. This ratio is 0.07; 0.14camera,shipmodels,datainterface,computer,electric and 0.28 for each ribblet form.read on the computer.20.5RTCTSV=VFrgL=ReVLv=(%) 100%C CT TODRCTO= World Appl. Sci. J., 32 (4): 577-581, 2014579Figure 3 shows the ribblet form. It can be shown thatthere is 3 variation ribblet form. Scalloped form, blade formandsawtoothformareusedinthisexperiment.Forallribblet form, have ratio heigh per length (h/s) is 0.3.Analyzes: The resistance offered by a ship to movementthroughwatermayberesolvedintotwoprincipalcomponents: frictional resistance and residual resistance.The most widely used estimation of mono-hull resistanceis the method proposed by ITTC. Total resistance coefficient can be defined as:C= (1 + k) C+ C (1)T F wCis total resistance coefficient, Cis frictional resistance ScaloopedT Fcoefficient, Cis wave resistance coefficient, (1+k) is formWfactor andcanobtainedbytowingtanktestresultsfor model with scalloped ribblet compared to the ship modelthe models.withoutribblet.TheshipmodelwithscallopedribbletThe totalresistancecoefficientC hasbeen placed will be varied for 3 variations of ratio area with totalTcalculated as: wettedhull.Resultsshowsthatthetotalvalueofthe(3) trend.Thevalueoftotalresistancecoefficient(C )shipWhereiswater density andS is the wetted area of the all ship model with ribblet sticking have positive effects,ship hull. as indicated by the value of total drag coefficient is lowerTheFroudesnumberandReynoldsnumberare than the ship without ribblet. defined as:In the turbulent-flow regime, fluid resistance typically(4) owing totheshearstressesatthesurfaceactingacross(5) interactingwiththetipsonlyandrarelycausinganyWhere Visthespeedoftheship,Listhelengthofthe higher velocity vortices interact only with a small surfaceship, gisaccelerationofgravityand isthekinematic area at the riblet tips, only this localized area experiencesviscosity of water. high-shearstresses.Thelow-velocityfluidflowintheDrag reduction is obtained by: across the majority of the surface of the riblet. Based on(6) ribblet is 7% in Lr/Lk = 0.28. The ratio of drag reductionwhere C isthetotalcoefficientresistanceofship Figure5showstheRelationshipbetweentotalTOwithout ribblet and C is the total coefficient resistance of resistance coefficient (C ) and Froude number (Fr) for shipTship with ribblet form.modelwithbladeribbletcomparedtotheshipmodelRESULTS AND DISCUSSION willbevariedfor3variationsofratioareawithtotalFigure4showstheRelationshipbetweentotal shipmodelwithribbletisgreaterthanmonohullmodelresistance coefficient (C ) and Froude number (Fr) for ship with the samedisplacementatFr 0.2 forincreasesdramaticallywithanincreaseinsurfaceareathe new,largersurfacearea.However,asvorticesformabove aribletsurface,theyremainabovetheriblets,high-velocity flow in the valleys of the riblets. Since thevalleysoftheribletsproducesverylow-shearstressesfigure4,itobtaineddragreductionratioforscallopeddecreaseswithdecreaseofratioarearibbletperwettedsurface area hull ship. Twithout ribblet. The ship model with blade ribblet placedwetted hull. The value of total resistance coefficient (C )TWorld Appl. Sci. J., 32 (4): 577-581, 2014580Fig. 5: Total Resistance Coefficient of Ship with Ribblet showsthattheshipmodelwithribbletprovidesmallerBlade totalresistancecoefficientthanshipmodelwithoutFig. 6: Total Resistance Coefficient of Ship with RibbletSawtooth This work in sponsored by Directorate of Researchat Fr > 0.2 for all ship model with ribblet sticking have scheme Riset Awal UI 2013.positive effects, as indicated by the value of total dragcoefficient is lower than the ship without ribblet. REFERENCESBlade riblets have been rigorously studied intheir characteristic dimension ratios. Due to their inherent 1. Shephard, K.L., 1994. Functions for fish mucus,weak structure, optimal blade riblet thickness is limited Rev. Fish Biology and Fisheries, 4: 401-429.by strength, not fluid dynamics. Blades that are too 2. Hoyt, J.W., 1975. Hydrodynamic drag reduction duethin will warp in fluid flow and allow vortices to to fish slimes. pp: 653-673 in T.V.T. Wu, C.J. Brokawtranslate as a result. So for blade ribblet has higher and C. Brennon, Eds., Swimming and flying in nature.drag reduction. Effect of ribblet is generated regular Plenum Press, New York.turbulent to the fluid flow so the resistance will be 3. Ripken, J. and M. Pilch, 1964 "non-Newtonian pipedecreases. The value of drag reduction for blade ribblet friction studies with various polymer waterup to 10%. solutions." St. Anthony Falls Hydraulic Laboratory,Figure 6 shows the Relationship between total University of Minnesota. Minneapolis.resistance coefficient (C ) and Froude number (Fr) for ship Minn (Project Report No. 7 1).Tmodel with blade ribblet compared to the ship model 4. Rosen and E. Conford Neri, 1970. Fluid Friction ofwithout ribblet. For the same h/s, blade riblets have the The Slime of Aquatic Animal. Technical Publicationsmallest shift in the effective flow origin due to their small of Naval Undersea Research and Developmentcross sectional area and sawtooth have the largest shift Centre Department of The Navy.in the effective flow origin. When comparing the optimaldragreductiongeometriesforsawtooth,scallopedandblade riblets shown in figure 3, it is clear that blade ribletsprovidethehighestlevelofdragreduction,scallopedribletsprovidethesecondmostandsawtoothribletsprovide the least benefit. The drag reduction of sawtoothribblet is nearly similar with scalloped ribblet. There is 4%drag reduction is occured.CONCLUSIONThis paper experimentally investigates the influenceofspecialroughness(ribblet)onthewallofshipmodelribblet with equal displacement. Fluid drag in the turbulentboundary layer is, in a large part, owing to the effects ofthe streamwise vortices formed in the fluid closest to thesurface.Turbulenceandassociatedmomentumtransferintheouter boundary layers is, in a large part, owing tothetranslation,ejectionandtwistingofthesevortices.Additionally,thevorticesalsocausehighvelocitiesatthe surface that create large shear stresses on the surface.The mechanism of drag reduction with ribblet is generatedregular turbulent in the buffer layer. The maximum dragreductuoninthisresearchis10%forbladeribbletwithLr/Lk = 0.28.ACKNOWLEDGEMENTand Community Services, University of Indonesia withWorld Appl. Sci. J., 32 (4): 577-581, 20145815. Yanuar, Talahatu, Sunaryo, Warjito, 2011. 7. Choi, K.S., G.E. Gadd, H.H. Pearcey, A.M. Savill andDrag Reduction in Ship Model by Biopolymer of S. Svensson, 1989. Tests of dragreducing polymerSlime MonopterusAlbus Solution in Wall. Intl Jurnal coated on a riblet surface, Appl. Sci. Res.,Mekanikal Univ. Teknologi Malaysia, 32: 96-107. 46: 209-216.6. Yanuar, Gunawan, Sunaryo and A. Jamluddin, 2012. 8. BrianDeanandBharatBhushan,2010.Micro-bubbleDragReductiononaHighSpeed Shark-skinsurfacesforfluid-dragreductioninVessel Model.JournalofMarineandScience turbulent flow: a review, Phil. Trans. R. Soc. A 2010Application, 11: 301-304. 368, 4775-4806, doi: 10.1098/rsta.2010.0201.