| Surface effects limit the performance of hypersonic vehicles, micro-electro-mechanical devices, and directed energy systems. This research develops methods to predict adsorption, scattering, and thermal desorption of molecules on a surface. These methods apply to physisorptive (adsorption and scattering) and chemisorptive (thermal desorption) gas-surface systems. Engineering and design applications will benefit from these methods, hence they are developed under the Direct Simulation Monte Carlo construct.;The novel adsorption and scattering contribution, the Modified Kisliuk with Scattering method, predicts angular and energy distributions, and adsorption probabilities. These results agree more closely with experiment than the state-of-the-art Cercignani-Lampis-Lord scattering kernel. Super-elastic scattering is predicted. Gas-adlayer interactions are included for the first time. Accommodation coefficents can be determined by fitting simulations to experimental data.;The new thermal desorption model accurately calculates angular, translational, rotational, and vibrational distributions, and the rotational alignment parameter. The model is validated by comparing with experiments. Multiple transition states are considered in a set of non-dimensionalized equations of motion, linked with temporally-accurate event timing. Initial conditions are chosen from a new truncated Maxwell-Boltzmann distribution. Run times are improved by eliminating the Gaussian Weighting of desorbing products. The absorption energy barrier is shown to significantly contribute only to the translational energy of desorbing molecules by contributing energy to each adatom in a similar manner. |
