2018/3/11 Aerodynamic Effect of Airfoil Parameters 园上声克大婆 Airfoil Stall Characteristics 国上清大学 ,LE Radius(缘辛径)-lift coefficient,wave drag,transition Different stall characteristics for airfoils with different leading edge radius.thickness Thickness-to-chord ratio(t/c,相对厚度)-wave drag,stall Different airfoil sections can be used at the wing root and tip characteristics,lift coefficient,and structural weight Stall characteristics(失速特性) (round LE,14%t/c),separation start from TE,and loss of lift Fat airfoils Thinner airfoils Very thin airfoils Thinner airfoil (6-14%t/c),stall from the LE SEPARATION BUBBLE 螺 AE 宽RTD o r nd 0171 Soor an0 Structural Effect of Airfoil Parameters 圆上清文大些 Transonic Airfoils 国上清支大峰 Smaller weight for higher t/c value For high speed airfoils,the flow accelerates to supersonic over the More volume for higher t/c value,often imposed as constraints upper surface,forming shock wave,leading to high wave drag onstraints at certain chord locations to accommodate One solution is to use supercritical airfoils Where the shock wave is minimized or even eliminated Smaller range for C.G.Range,better for structural design eagaea2-w58 8oa6o0e四k-a88 Supercritical airfoil(超临界翼型) 国上洋大坐 Flow over conventional and supercritical airfoils 图上活大坐 Intuitive reasoning Pressure Strong shock distributions wave Extending the drag divergence Mach Number SC()designed mainly by contour modification and wind tunnel testing SC(D)designed using transonic,viscous analysis code 52018/3/11 5 © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics, 2017-2018 Aerodynamic Effect of Airfoil Parameters • LE Radius（前缘半径） – lift coefficient, wave drag, transition • Thickness-to-chord ratio (t/c,相对厚度) – wave drag, stall characteristics, lift coefficient, and structural weight • Stall characteristics（失速特性） – Fat airfoil (round LE, 14%t/c), separation start from TE, and loss of lift is gradual – Thinner airfoil (6-14%t/c), stall from the LE © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics, 2017-2018 Airfoil Stall Characteristics • Different stall characteristics for airfoils with different leading edge radius, thickness • Different airfoil sections can be used at the wing root and tip Fat airfoils Thinner airfoils Very thin airfoils © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics, 2017-2018 Structural Effect of Airfoil Parameters • Smaller weight for higher t/c value • More volume for higher t/c value, often imposed as constraints • t/c value constraints at certain chord locations to accommodate spar structure • Smaller range for C.G. Range, better for structural design © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics, 2017-2018 Transonic Airfoils • For high speed airfoils, the flow accelerates to supersonic over the upper surface, forming shock wave, leading to high wave drag • One solution is to use supercritical airfoils – Where the shock wave is minimized or even eliminated © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics, 2017-2018 Supercritical airfoil（超临界翼型） 29 Extending the drag divergence Mach Number SC(I) designed mainly by contour modification and wind tunnel testing SC(II) designed using transonic, viscous analysis code Increased drag divergence angle, but increased friction drag Intuitive reasoning © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics, 2017-2018 Flow over conventional and supercritical airfoils 30 Pressure Strong shock distributions wave