Parallel, Adaptive Finite Element Methods for Chemically
Reacting Flow Simulations
K.D. Devine, J.N. Shadid, A.G. Salinger, H.K. Moffat, and S.A. Hutchinson,
G.L. Hennigan
Sandia National Laboratories
Albuquerque, New Mexico 87185
Abstract
MPSalsa [5, 7] is a computer program developed at Sandia National Laboratories
that solves coupled three-dimensional fluid flow and detailed reaction
chemistry systems for modeling chemically reacting flow, such as flow in
Chemical Vapor Deposition (CVD) reactors. MPSalsa uses an unstructured finite
element mesh to model complicated geometries. Thermal diffusion, variable
physical properties, and mixture-averaged and true multicomponent diffusion
are included. Both gas and surface reactions can be modeled using the Chemkin
and Surface Chemkin libraries [1, 4]. An inexact Newton method is used to
solve the nonlinear system of fully-coupled equations [2]. The Aztec library
[3] of preconditioned Krylov iterative solvers is used to solve the resulting
linear systems. MPSalsa and Aztec have been optimized for high performance on
massively parallel computers. Peak speeds of 65 gigaFLOPS have been achieved
on Sandia's Intel Paragon computer [6].
To capture features such as steep gradients in species concentrations in
chemically reacting flow solutions, an automated adaptive mesh refinement
strategy is used. Adaptive methods have been used with great success for a
variety of mechanics and fluid flow problems. Their use on parallel computers,
however, is complicated by the need for distributed data structures, dynamic
load balancing, data migration, and maintenance of a distributed element
database. In this talk, we describe the data structures and strategies used
for adaptive mesh refinement and dynamic load balancing in MPSalsa. Results
demonstrating the performance of adaptive refinement and load balancing will
be shown.