Atwo-dimensionalsteadyReynolds-averagedNavier–Stokes(RANS)equationwassolvedtoinvestigatetheeffectsofaGurneyflaponSFYT15thickairfoilaerodynamicperformance.Thisairfoilwasdesignedforflightvehicleoperatingat20kmaltitudewithfreestreamvelocityof25m/s.Thechordlength(C)is5mandtheReynoldsnumberbasedonchordlengthisRe=7.76×105.Gurneyflapswiththeheightsrangingfrom0.25%Cto3%Cwereinvestigated.Theshearstresstransport(SST)k-ωturbulencemodelwasusedtosimulatetheflowstructurearoundtheairfoil.ItisshowedthatGurneyflapcanenhancenotonlytheprestallliftbutalsolift-to-dragratioinacertainrangeofanglesofattack.Specially,atcruiseangleofattack(α=3°),Gurneyflapwith0.5%Cheightcanincreaselift-to-dragratioby2.7%,andliftcoefficientby12.9%,respectively.Furthermore,thesurfacepressuredistribution,streamlinesandtrailing-edgeflowstructurearoundtheairfoilareillustrated,whicharehelpfultounderstandthemechanismsofGurneyflaponairfoilaerodynamicperformance.Moreover,itisfoundthattheincreaseofairfoildragwithGurneyflapcanbeattributedtotheincreaseofpressuredragbetweenthewindwardandtheleewardsidesofGurneyflapitself.
