Influence Research on Stability Margin for Flying Wing Configuration

Abstract

Reduction of trim loss is essential to raise lift-to-drag ratio and enhance flight control performance for flying wing configuration,so the influence on aerodynamic optimization of transonic flying wing configuration is studied based on discrete adjoint method,and three conditions of 10%,0%,-10%stability margin are considered in the optimization process,respectively.The free-form deformation(FFD)method is used to achieve the parametrization of surface unstructured grid,the control point of FFD is selected to serve as design variable,and the flowfield and adjoint equation is solved to obtain the sensitivity information.The sequential quadratic programming(SQP)algorithm is utilized to obtain the gradient of control points,and the final configuration is obtained by multiple iteration.The results show that the discrete adjoint optimization method can evidently improve the maximum lift-to-drag ratio under the constraint of geometric thickness and moment trim,and the increment is exceeded by 8%at these three conditions.The increment of cruise lift-to-drag ratio appears to reduce with the increase of stability margin while lift coefficient is fixed,the lift-to-drag ratio can increase 5.08%when the stability margin is 10%.

Keywords

• flying wing configuration
• discrete adjoint
• aerodynamic optimization
• stability margin
• lift-to-drag ratio