Implicit multigrid schemes for challenging aerodynamic simulations on block-structured grids

In this paper, the use of implicit multigrid smoothers for challenging aerodynamic simulations is explored. The block lower-upper symmetric Gauss-Seidel (LU-SGS) and hybrid Runge-Kutta/LU-SGS schemes are implemented in Bombardier's multiblock Navier-Stokes solver, FANSC. The schemes are compared to the existing Runge-Kutta and point-Jacobi preconditioned explicit multistage smoothers. Through tests ranging from 2D airfoils to 3D wing-body-engine cases, the computational speed-up and robustness of the implicit schemes are evaluated. It is shown that the implicit smoothers present a computational speed-up of at least two, and are significantly more robust, especially for flow problems involving the "power-on" engine boundary condition. (C) 2011 Elsevier Ltd. All rights reserved.