A Spectral-Lagrangian Boltzmann Solver for a Multi-Energy Level Gas

In this paper a spectral-Lagrangian method for the Boltzmann equation for a multi-energy level gas is proposed. Internal energy levels are treated as separate species and inelastic collisions (leading to internal energy excitation and relaxation) are accounted for. The formulation developed can also be used for the case of a mixture of monatomic gases without internal energy (where only elastic collisions occur). The advantage of the spectral-Lagrangian method lies in the generality of the algorithm in use for the evaluation of the elastic and inelastic collision operators. The computational procedure is based on the Fourier transform of the partial elastic and inelastic collision operators and exploits the fact that these can be written as weighted convolutions in Fourier space with no restriction on the crosssection model. The conservation of mass, momentum and energy during collisions is enforced through the solution of constrained optimization problems. Numerical solutions are obtained for both space homogeneous and space inhomogeneous problems. Computational results are compared with those obtained by means of the DSMC method in order to assess the accuracy of the proposed spectral-Lagrangian method

Joydeep GhoshOn Approximation Structures for Nonlinear Systems

I am grateful to my supervisor, Professor Irwin Sandberg, for his help with this dissertation. It has been a great pleasure to work with someone who so enjoys the beauty of System Theory, and who has explored it so extensively. I greatly appreciate his instruction, help, and patience, and I admire his relentless curiosity. His continued supervision of my dissertation during his retirement is especially appreciated. I also appreciate the help of those who served on my dissertation committee