Effects of Freestream Turbulence on Wing-Surface Flow and Aerodynamic Performance

The effects of freestream turbulence intensity on the surface-e ow characteristics, including separation, bubble, leading-edge bubble, turbulent separation, and three-dimensional e ow, as well as the corresponding aerodynamic performance, including lift, drag, and stall, of a cantilever NACA 0012 wing model have been studied in a wind tunnel. Different wire-mesh screens were placed between the nozzleand test section to produce various freestream turbulence intensities. The characteristic regimes of surface e ow were identie ed by using the surface-oil e ow technique. The aerodynamic lift and drag were measured with a PC-based force/moment sensing system. The variationsofliftanddragwerefoundtobecloselyrelatedtothebehaviorofsurfacee ow.Thefreestreamturbulence signie cantlyaffectsthesurfacee owandaerodynamicperformance.Thesurfacee owandlift/dragatlowfreestream turbulenceareapparentlydifferentfrom thatatlargefreestreamturbulenceintensity.Theine uenceisdrasticwhen turbulence intensities are smaller than about 0.45%, whereas it becomes insignie cant when turbulence intensities are greater than 0.45%. Details of the ine uences are discussed and illustrated.