Progress in Meshing for Dynamic High-Lift CFD

Abstract

The present work addresses improvements for mesh generation of unstructured and multi-block structured grids for rigid body motion applications. The activities are concerned with local re-connection and local refinement approaches in order to obtain high-quality meshes for the simulation of the full deployment of a Krueger leading-edge device. Local reconnection offers a suitable way to implement a re-meshing strategy based on the Chimera approach that eliminates the need for non-conservative interpolation. The strategy is based by replacing overlapping mesh regions by a conformal triangulation. An initial multi-block structured grid and a Chimera grid are used for the development and assessment of the local reconnection approach. The full sequence of a Krueger flap deflection has been obtained on meshes that differ significantly in mesh resolution (1:4). The mesh quality of the interfacing meshes has been assessed based on established mesh quality criterions. It shows that the local reconnection retains the anisotropy of the baseline mesh over the full deflection range of the Krueger flap. Due to the triangulation, a slightly higher size variation is observed than in the baseline mesh. The method has been shown to be robustly implemented. The block-structured local grid refinement method aims for a uniform mesh spacing by first refining the block topology and subsequently refining the grid per block. The smoothness of the locally refined grid is maintained by an appropriate smooth interpolation of the original grid-point distribution. The refined grid attached to a solid surface is mapped onto the original geometry definition in order to preserve the correct aerodynamic shape. The local grid refinement capability is combined with the Chimera approach to perform unsteady simulations of Krueger device deployment. Here, local grid refinement is employed to arrive at similar grid resolution on both sides of the Chimera interface in order to improve the interpolation accuracy. The validity of the method is demonstrated by a refined Chimera grid which has been generated around the DLR F15 airfoil with a Krueger device. The grid around the main wing has been locally refined in order to obtain a uniform grid point distribution in the region downstream of the Krueger device where turbulence must be resolved.