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LaminarFountainsWhatarethey?PostedonJune17,2014

Waterwatereverywhere!Therearenotwowaysaboutit,waterfountainsarejustplainfun.Showawaterfountaintoanyfiveyearoldandjustseeiftheydontstartplayingandgiggling.Whichleadsmetothisconclusion:InevergrewupbecauseIstillgetaridiculousgrinonmyfacewhenIgettoplayinawaterfountain.Andthecoolestofallthefountainsin

Myfirstworkinglaminarfountain

ScuttlebotsCircuits,Robotics,andOOooShiny!

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myopinionisthelaminarfountain.Ibuiltalaminarfountainafewyearsbackandamnowworkingondesignsfora3DPrintedlaminarfountainwhichIwillpostonlineonceIgetasemiworkingalphaversion.Inpreparationforallthatletmeexplainalittleaboutwhatlaminarflowandfountainsare.

Whatislaminarflow?Thesimplestwaytoexplainlaminarisprobablytosaythatitistheoppositeofturbulentflow.Turbulentflowisthemostcommontypeofflowyouwillseeinnature.Adrinkingfountainisagoodexampleofturbulentflowwithhowblobbyandwigglythewateriswhenitcomesout.Whitewaterrapidsinariverwouldbeanextremecaseofturbulentflow.Soincontrast,laminarflowissupersmoothflowingliquidorgas.Thefullrealityoflaminarflowisthatitmeansallofthewaterparticlesareflowingexactlyparalleltoeachother,inthesamedirection,andassucharenotbumpingintooneanother.

Laminarflowprofileshowingthevelocityofwaterasitmovesthroughapipe.(Takenfromwikipedia)

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Sowhyitcool?Becauseitsscience!Butalsobecauseithassomereallycoolapplicationpropertieswecanmakeuseof:

1)ItsmovingbutsitdoesntlooklikeitBecausealaminarstreamisperfectlysmooththeflowpathwillstayinexactlythesameplaceatalltimes.Atraditionalfountainwillwobbleandsputterasitpumpswateroutwhichmakesitveryobviousthatthewaterismovingsinceyoucanfollowtheindividualwaterblobsastheypassthroughtheair.Alaminarstreamisperfectlyuniformanddoesnotwaverwhichmeanstherearenowindividualwaterdropletstofollowwithyoureyes.Thewaterisflowingquicklybutitshardtotell.Itliterallylookslikeaperfectglassarchcomingfromthefountaingoingallthewaytowhereithitslands.(Seethepictureabove)

2)NosplashBecausethewaterstreamissosmoothitwillnotbreakapartwhenitencountersanotherbodyofwaterorsmoothobject.Ifitlandsinapoolofwateritwilldisappearwithoutatrace.Ifyouputasmoothballinitswayitwillspreadoutandwraparoundtheballwithoutsplashing.Itsareallycooleffectandalsohasthebenefitofmakingitquiettoo!

Realworldpictureofalaminarwaterstreamafteritexitsmylaminarfountain.Becausethewaterisallflowinginthesamedirectionitstaysperfectlytogetherandcreatesaglassrodeffectwherelightcanpassrightthrough.

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3)ItJumpsBecausetheflowstreamissosmoothithasaniftyvisualeffectwhenyousuddenlyblockthestream.Itlookslikethestreamisjumping.Thewaterthatisnotblockedcontinuestoflythroughtheairontheoriginalpathandstaystogether.Yougetlittlewatersnakesthatthatflythroughtheair.Ifyoustringmultiplefountainstogetheryoucancreatetheillusionthatwaterisjumpingfromonefountaintothenext.

4)IttransmitslightlikeafiberopticcableAfiberopticcableisaperfectlysmoothmediumthattransmitslightfromoneendtotheother.Theperfectlysmoothsidesofthecablereflectthelightinsidebackintothecabletokeepitbouncingdownthelengthuntilitreachestheotherend.Alaminarstreamalsohassupersmoothsidesandthereforewillalsobouncelightbackinsideofitself.Thismeansthatifyoushineabrightenoughlightdirectlyintothelaminarstreamitwilllightupallthewayfromendtoend!Evenaroundthecurve!

HereisacoolvideothatshowsthelaminarfountainforumuserMagicNozzlepostedofhishomemadefountainthatdemonstratesseveraloftheseproperties(feelfreetoskipahead,thenightshotsattheendareespeciallycool).OriginalforumpostHERE

LaminarMaths:Ifyoureintomathandtheequationsthatgovernwhenastreamislaminarthanthisisthesectionforyou.Ifinditsupercoolhowthisworkssoletsdigin!

Inanengineeringfluiddynamicsclass(studyofmovingliquids,areallyfuncourse)youlearnabouttheReynoldsnumberwhichwilltellyouifafluidsflowislaminar,transitional,or

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turbulent.HereistheequationfromWikipedia:

Holdon,wellkickthatscaryequationintheteeth.Letsstartbyfocusingonthefirstvariationoftheequationlisted.

Re=(p*v*D)/u

Twoofthoseareactuallyconstants.pisthedensityofwaterwhichwecangoogle(1000Kg/m^3)anduisthedynamicviscosityofourfluid(wateris0.000404atroomtemperature).Soputtingthosebackinandsimplifyingwegetthis:

Re=(2.47510^6)*v*D

Thatsnotsobad.visthevelocityofourfluidinthepipeinmeterspersecondandDistheinternaldiameterofourpipeinmeterswhichshouldbeprettyeasytocalculate.OncewehaveourReynoldsNumber(Re)wecanseeiftheflowwillbelaminar.AnRevaluebelow2300meansthattheflowisLaminar.AnRevaluebetween2300and4000isTransitionalandanRevalueabove4000isTurbulent.AllthismeansthatweneedtoadjustourwatervelocityandpipediametertogetanRebelow2300forourfountain.Thatsallthemath!

Howthemathworksinreallife:Sonowthatwehavethemath(ortrustmeifyoudidntreadit)wecaninterpretit.Thisiswhatitallboilsdowntoinreallife:

AHHHHHH!!!1!1!!Maths!*DeepBreath*Thisequationisactuallysupersimplesoholdonandkeepreading.

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Thefasterthevelocityofthefluidandthebiggerthepipe,themoreturbulenttheflowwillbe.

Orinversely:

Theslowerthefluidandthesmallerthepipethemorelaminartheflowwillbe.

Sotoputthisintotherealworldletstackleoneproblematatimeandstartwithvelocity.Weneedacertainminimumamountofvolumeflowtoachievethefountainsizewewant.Forinstance,thepumpIusedinthepicturesaboveisratedat500gph(gallonsperhour)whichgavemethenicebigwaterarchyousee.Theproblemshowsupnowinthatthevelocityisfoundbydividingtheflowratebythecrosssectionalareaofthepipewhichisafunctionofpipediameteraswell!SoweneedabiggerdiametertoslowthevelocitydownbutasmallerdiametertogetalowreynoldsnumberCrap.

ButwhatifItoldyouwecouldhaveaseparatediametertouseforvelocityandthediameterintheReynoldsequation?Thetrickistotakealargepipe(8inchPVChere)andpackitfullofsmallpipes(drinkingstraws).ThiswayyougettousethelargediameterofthePVCforthevelocitypartandthesmallindividualdiametersofthedrinkingstrawsfortheReynoldsdiameter.Bingo!Wecannowachievelaminarflow!

Insidemylaminarfountainarenearly2000drinkingstrawstogiveasmalldiametertothewaterflowingthroughwhilekeeptheslowvelocityofabig8inchouterpipe.

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3THOUGHTSONLAMINARFOUNTAINSWHATARETHEY?

Theorycraftingcomplete!Thatsitforthewhatalaminarfountainis.StaytunedforsomemorepoststalkingaboutmyfirstlaminarfountainandhowIamhopingtousemy3DPrintertostartanewcycleofdesigns!

SHARETHIS:

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conneronJuly5,2014at6:39amsaid:

Ilookedaroundtheforumbuticouldntfindasupplylist.

PaulonJanuary7,2015at3:54pmsaid:

Hi

Yourlaminairstreamlooksamizing.

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Howdoyoucreatethecoppercolorednozzle?

ihayes42onJanuary7,2015at4:48pmsaid:

Iactuallypurchasedthatfromaguyontheforumsathttp://laminar.forumotion.com/Itsasmallcopperdiscthatwasturnedonalathe.Hefoundawebsitewhereyoucanputupsmallpartsformachineshopstobidontofilltheirdowntime.IreallywishIknewwhichsitethatwasasIwouldlovetogetmyownrun.Ivebeenmeaningtogobackanddosomeresearchonthat.IllseewhatIcanfindout

PSIvealso3DPrintedsomenozzlesnowandwhiletheydoworkdecentlytheyarentquitethesamecaliberasthemachinedonesIhave.