Parallel algorithms and software for multi-scale modeling of chemically reacting flows and radiative heat transfer

Multi-scale modeling, the simulation of coupled physical processes that occur on different temporal or spatial scales, is becoming an increasingly important area of research in computational science. Solving such problems can be computationally intensive; however, because of the increasing availability of large computational resources, their solution can be feasible. An important multi-scale application is the numerical simulation of combustion. In combustion, three different physical processes govern the dynamics of the problem: fluid flow (which can be turbulent or laminar), chemical reactions, and heat transfer, with radiative heat transfer being a dominant mode. The objective of this thesis is to create efficient sequential and parallel algorithms and software that improve accuracy and performance of combustion applications. Another purpose of this work is to create clean, easy-to-use software interfaces that can be readily used from both C/C++ and FORTRAN applications without significant changes to the original code. In this thesis, we introduce two new software systems that enable modeling of multi-scale phenomena in combustion applications on single processor and distributed memory multiprocessor systems and improve their accuracy and performance. The first system is called the Database On-Line for Efficient Function Approximation (DOLFA) for speeding up chemistry calculations in combustion applications. A second system, called Photon Monte Carlo (PMC) [1], is used for solving the Radiative Transfer Equation (RTE) by calculating the radiative heat fluxes for the volume elements of a computational mesh. The PMC software system is capable of handling computational domains with complex enclosures and various radiation configurations.