Semi-Empirical Prediction of Aircraft Low-Speed Aerodynamic Characteristics

Erik D. Olson
2015 53rd AIAA Aerospace Sciences Meeting   unpublished
This paper lays out a comprehensive methodology for computing a low-speed, high-lift polar, without requiring additional details about the aircraft design beyond what is typically available at the conceptual design stage. Introducing low-order, physics-based aerodynamic analyses allows the methodology to be more applicable to unconventional aircraft concepts than traditional, fully-empirical methods. The methodology uses empirical relationships for flap lift effectiveness, chord extension,
more » ... coefficient increment and maximum lift coefficient of various types of flap systems as a function of flap deflection, and combines these increments with the characteristics of the unflapped airfoils. Once the aerodynamic characteristics of the flapped sections are known, a vortex-lattice analysis calculates the three-dimensional lift, drag and moment coefficients of the whole aircraft configuration. This paper details the results of two validation cases: a supercritical airfoil model with several types of flaps; and a 12-foot, full-span aircraft model with slats and double-slotted flaps. Nomenclature c d , C D sectional drag coefficient, total drag coefficient c dp0 zero-lift sectional profile drag c f , c s trailing-edge flap chord, leading-edge flap chord c l , C L sectional lift coefficient, total lift coefficient c l max , C L max maximum sectional lift coefficient, maximum total lift coefficient c l0 sectional lift coefficient at α = 0 c lα , C Lα sectional lift-curve slope, total lift-curve slope c section chord k d trailing-edge flap profile-drag increment factor k s leading-edge flap maximum lift factor M Mach number Re c Reynolds number based on chord α angle of attack α δ effective angle of attack factor δ f , δ s trailing-edge flap deflection, leading-edge flap deflection Δ f , Δ s trailing-edge flap increment, leading-edge flap increment Δy leading-edge sharpness parameter η δ trailing-edge flap effectiveness factor θ f , θ s trailing-edge flap chord function, leading-edge flap chord function
doi:10.2514/6.2015-1679 fatcat:xkvekskioncpnobjx55tgysh2q