Synthesis of Aerodynamic Force Characteristics of Bisymmetric Lifting Vehicles

摘要

The dependences of lift and drag coefficients on angle of attack for bisymmetric lifting vehicles are synthesized using two simplifying assumptions: (1) the axial force coefficient is independent of the angle of attack, and (2) the normal force coefficient increases linearly with the angle of attack. Good agreement with experimental data is found for the value of the the angle of attack at which the maximum L/D occurs and the angle of attack for maximum C sub L in the hypersonic regime; applicability for subsonic flight is limited to those angles of attack below the inception of flow separation. Conditions for terminal equilibrium glide and landing for aircraft are derived from the simplified aerodynamic characteristics. With the linearized normal force, the following useful rules of thumb are obtained for super and hypersonic vehicles with maximum L/D greater than 1.0: (1) the drag at maximum L/D is very closely twice the zero-lift drag, (2) the L/D at maximum C sub L is about 0.8, (3) the angle of attack for maximum C sub L is about 48 deg, (4) the ratio of the maximum C sub L to the C sub L at L/D max is approximated by 0.5 + L/D(max), and (5) the ratio of the normal force slope to the maximum lift is closely 2.0 per radian. (Author)