Efficient Mesh Deformation for Computational Stability and Control Analyses on Unstructured Viscous Meshes

This paper documents the initial development results of an efficient mesh deformation technique to support the modeling of elastic aircraft with traditional aircraft control surfaces in high-fidelity computational fluid dynamics (CFD) simulations on unstructured meshes. Even though unsteady Navier-Stokes simulations of full-scale aircraft are routinely computed on meshes with tens of millions cells to support current stability and control analyses, these simulations still take on the order of days to complete on state of the art computing clusters. Thus, as multi-disciplinary simulations incorporating CFD solutions are applied to full aircraft configurations, it is imperative that the supporting mesh deformation schemes are extremely efficient and robust. The techniques developed here are based on localized, algebraic-deformation schemes. These types of schemes are known to be computationally cheap but commonly suffer from robustness issues, especially when applied to flight Reynold’s number viscous meshes where some element aspect ratios are on the order of one million. To alleviate these issues, a two-phased approach is used where a “viscous layer ” of grid nodes is moved rigidly with the deforming boundary surface, and a separate scheme is used for the remaining nodes in the outer region. A modified surface influence scheme is investigated for the outer region deformation as well as a modification of a scheme based on mapping nodes in a Delaunay triangulation between the deforming boundary and the farfield. The mesh deformation schemes are applied to a flapped 2D NACA airfoil and a conventional aileron on a NACA 0015 wing. The computational efficiency of the technique is discussed, and qualitative comments are made regarding the mesh cell quality throughout the full range of boundary motions. The associated benefits regarding a-priori exercising of the computational grid are also discussed. I