2018/3/11 How Aspect Ratio Relates to Wing Drag 圈上声文大学 Quick Estimation of Cp 国上洋文大坐 Aerodynamic efficiency of wing-only configuration depicted by the relations between L/D Aspect Ratio Valid in comparisons between the same configuration osdra due to lift (skin friction and pressure Fuselage or configuration is the additional factor to consider ·Or in another form Oswald factor is a better parameter used to calculate the draa Cp K C K2CL Cop where,="K=-2K",and Coo=Comim+K"Cmm (drag at zero lift) r n 7 Soor an0 62018/3/11 6 © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics, 2017-2018 How Aspect Ratio Relates to Wing Drag • Aerodynamic efficiency of wing-only configuration depicted by the relations between • L/D ~ Aspect Ratio • Valid in comparisons between the same configuration • Fuselage or configuration is the additional factor to consider • Oswald factor is a better parameter used to calculate the drag © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics, 2017-2018 Quick Estimation of 𝑪𝑫 • Conventional form of the lift-drag-polar equation can be given as 𝐶஽ = 𝐶஽௠௜௡ + 𝐾ᇱ𝐶௅ଶ + 𝐾ᇱᇱ 𝐶௅ − 𝐶௅௠௜௡ ଶ • where 𝐾 ᇱ is the inviscid drag due to lift and 𝐾 ᇱᇱ is the viscous drag due to lift (skin friction and pressure drag). • Or in another form 𝐶஽ = 𝐾ଵ𝐶௅ଶ + 𝐾ଶ𝐶௅ + 𝐶஽଴ • where, 𝐾ଵ = 𝐾ᇱ + 𝐾ᇱᇱ, 𝐾ଶ = −2𝐾ᇱᇱ𝐶௅௠௜௡, and 𝐶஽଴ = 𝐶஽௠௜௡ + 𝐾ᇱᇱ𝐶௅௠௜௡ ଶ (drag at zero lift)