Author: National Aeronautics and Space Administration (NASA)Publisher: Createspace Independent Publishing Platform
ISBN: 9781720572145
Category :
Languages : en
Pages : 30
Book Description
The efficiency gains obtained using higher-order implicit Runge-Kutta schemes as compared with the second-order accurate backward difference schemes for the unsteady Navier-Stokes equations are investigated. Three different algorithms for solving the nonlinear system of equations arising at each timestep are presented. The first algorithm (NMG) is a pseudo-time-stepping scheme which employs a non-linear full approximation storage (FAS) agglomeration multigrid method to accelerate convergence. The other two algorithms are based on Inexact Newton's methods. The linear system arising at each Newton step is solved using iterative/Krylov techniques and left preconditioning is used to accelerate convergence of the linear solvers. One of the methods (LMG) uses Richardson's iterative scheme for solving the linear system at each Newton step while the other (PGMRES) uses the Generalized Minimal Residual method. Results demonstrating the relative superiority of these Newton's methods based schemes are presented. Efficiency gains as high as 10 are obtained by combining the higher-order time integration schemes with the more efficient nonlinear solvers.Jothiprasad, Giridhar and Mavriplis, Dimitri J. and Caughey, David A. and Bushnell, Dennis M. (Technical Monitor)Langley Research CenterALGORITHMS; NAVIER-STOKES EQUATION; UNSTRUCTURED GRIDS (MATHEMATICS); MEASURE AND INTEGRATION; RUNGE-KUTTA METHOD; AGGLOMERATION; CONVERGENCE; LINEAR SYSTEMS; NONLINEAR SYSTEMS
