Viscous Aerodynamic Shape Optimization of Wing Body Configuration with Overset Mesh Techniques

Abstract

A new design approach for a delicate treatment of complex geometries such as wing/body configuration is arranged using overset mesh technique under large scale computing environment. For an in-depth study of the flow physics and highly accurate design, several special overlapped structured blocks such as collar grid, tip-cap grid, and etc. which are commonly used in refined drag prediction are adopted to consider the applicability of the design code to practical problems. Various pre- and post-processing techniques for overset flow analysis and sensitivity analysis are devised or implemented to adapt overset mesh technique to the design optimization problem based on Gradient Based Optimization Method (GBOM). In the pre-processing, the convergence characteristics of the flow solver and sensitivity analysis are improved by overlap optimization method. And the orphan cells under the surface at the block to block interface are treated by subcell transfinite interpolation for Navier-Stokes calculation. Moreover, a new post-processing method, Spline-Boundary Intersecting Grid (S-BIG) scheme, is proposed by considering the ratio of cell area for more refined prediction of aerodynamic coefficients and convenient evaluation of sensitivities under parallel computing environment. For the sensitivity analysis, adjoint formulations for overset boundary conditions are implemented into the fully hand-differentiated sensitivity analysis code. A smooth geometric modification on the overlapped surface boundaries and evaluation of grid sensitivities can be performed by mapping from planform coordinate to the surface meshes with Hicks-Henne function. Careful design works for the drag minimization problem of a wing/body configuration are performed using the newly-developed and -applied overset mesh techniques.