Improving the performance of the CFD code Edge using LU-SGS and line-implicit methods

The implicit LU-SGS solver has been implemented in the code Edge to accelerate the convergence to steady state. Edge is a ow solver for unstructured grids based on a dual grid and edgebased formulation. LU-SGS has been combined with the line-implicit technique to improve convergence on the very anisotropic grids necessary for the boundary layers. LU-SGS works in parallel and gives better linear scaling with respect to the number of processors, than the explicit scheme. The ordering techniques investigated have shown that node numbering does inuence the convergence and that the native orderings from Delaunay and advancing front generation were among the best tested. LU-SGS for 2D Eu-ler and line-implicit LU-SGS for 2D RANS are two to three times faster than the explicit and line-implicit Runge-Kutta respectively. 3D cases show less acceleration and need a deeper study.QC 20131219