Analysis on drag characteristic of busemann-type biplane

Abstract

Reducing wave drag caused by shock wave is one of the biggest challenge for supersonic aircraft. Busemann-type biplane could remarkably reduce wave drag by the interaction of shock and expansion waves. Using the Computational Fluid Dynamics (CFD) analysis methodology, the drag characteristic of Busemann-type biplane is investigated. For inviscid flow, the Busemann biplane can reduce wave drag near to zero. In case of viscous flow, affected by surface friction, there is an increase in the drag coefficient of the Busemann biplane. However, the increase is still less than half of the contrasted diamond airfoil's drag. The diamond airfoil chord length and thickness are the same as the Busemann biplane. The Busemann biplane has low drag characteristic at its designed Mach number. During the process of speeding up, the mass flow is choked between the biplane resulting in sharp increase in the drag. To resolve the flow chocking problem, a methodology is presented that combines dislocating biplane with deflecting slat and flap. This could change the inlet-to-throat ratio and pressure distribution to reduce the drag penalty. The resulting drag coefficient is considerably small compared to the original Busemann biplane and the diamond airfoil.