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超疏水性表面上的流体滑移及其减阻应用(英文).docx

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超疏水性表面上的流体滑移及其减阻应用(英文) SuperhydrophobicSurfaceFluidSlipandItsDragReductionApplications Introduction Inrecentyears,thedevelopmentofsuperhydrophobicsurfaceshasattractedincreasingattentionduetotheiruniqueproperties,suchasexcellentwaterrepellencyandlowfriction.Asuperhydrophobicsurfaceisdefinedasasurfacewithawatercontactanglegreaterthan150degreesandaslidinganglelessthan10degrees.Aliquiddropletonasuperhydrophobicsurfacewillformanearlysphericalshapewithverylittlecontactarea,whichisknownastheCassie-Baxterstate.Theairpocketstrappedintheroughstructuresofthesurfacecanprovidealow-shearinterfacefortheliquiddroplet,resultinginasignificantslipoftheliquid.Thefluidslipeffectonsuperhydrophobicsurfaceshasbeenstudiedextensivelyinrecentyears,andithasshownpromisefordragreductionapplicationsinvariousfields,suchasmicrofluidics,marinetransportation,andenergyconversion. FluidSliponSuperhydrophobicSurfaces Thefluidslipeffectonsuperhydrophobicsurfacesarisesfromtheairpocketstrappedinthesurfaceroughness,whichprovidesalow-shearinterfacefortheliquid.Thesliplength,whichisdefinedasthedistanceoverwhichtheliquidvelocityreachesitsno-slipboundaryconditionatthesolidsurface,canbecalculatedbythefollowingexpression: λ=δ(u-uf)/uf whereλisthesliplength,δistheroughnessheightofthesurface,uistheliquidvelocityatthesurface,andufistheliquidvelocityfarfromthesurface.Thesliplengthcanincreasedramaticallyonsuperhydrophobicsurfaces,whichhasbeenreportedtoreachuptotensofmicrometersorevenmillimetersundercertainconditions.Thefluidslipeffectonsuperhydrophobicsurfaceshasbeenobservedinvariousexperiments,suchasflowvisualization,micro-particleimagevelocimetry,andpressuredropmeasurements.Thefluidslipeffectcanbeenhancedbyincreasingthesurfaceroughness,decreasingtheliquidviscosity,orincreasingtheliquidsurfacetension. DragReductionApplications Thefluidslipeffectonsuperhydrophobicsurfaceshasbeensuggestedtohavepotentialapplicationsindragreduction.Inparticular,thereducedfrictionaldragonsuperhydrophobicsurfacescanleadtoenergysavingsinvar