Alla A. Batishcheva

Adaptively Meshed Fully -Kinetic PIC -Vlasov Model For Near Vacuum Hall Thrusters

Predictive modeling of Hall thrusters requires a new level of simulation capabilities with integrated multi-scaling and accurate anomalous transport models. A PIC-Vlasov hybrid model is undertaken utilizing adaptive meshing techniques to enable automatically scalable resolution of fine structures during the simulation. The code retains the versatility of a PIC simulation while intermittently recalculating and smoothing particle distribution functions within individual cells to ensure full velocity space coverage and to reduce numerical noise. Background theory and algorithmic details are briefly outlined, and numerous benchmarking results are used to demonstrate various portions of the simulation. Initial results of the application of this model to a relatively new and poorly theoretically understood concept in Hall thruster design, a so-called Near Vacuum Hall Thruster (NVHT), are presented and discussed. The importance and practical possibility of incorporating a self-consistent quench model for anomalous electron cross-field transport in 2D3V fully kinetic approximation is also explored.

Parallel fast solver based on the vortex element method

Publisher Summary This chapter summarizes the parallel implementation of a fast treecode solver utilizing the vortex element method for the computation of unsteady, incompressible, and high Reynolds number flows. The solver operates on the rotational and irrotational components of the velocity field separately. The rotational part is further split into convection and diffusion + vortex stretching parts. The former is treated in one module that is based on a treecode algorithm fully adapted for parallel architectures. The latter part utilizes the vortex redistribution method that is accelerated via a separate tree data structure and parallelization. The effect of solid boundary conditions will be incorporated by solving for the irrotational velocity component using the boundary element method and then introducing vorticity at the walls. The vortex-element approach solves the Navier-Stokes equations in vorticity transport form. The vorticity field is discretized as a set of vortex elements, whose strengths and positions are computed in space and time in the Lagrangian reference frame.

An efficient statistical noise-free kinetic method for collisional rarified gas simulations

Publisher Summary This chapter reviews a new grid method for the gas modeling in weakly-to-moderately collisional regimes. The method can be qualified as an operator-splitting scheme with analytical sub-steps. It can be utilized either exact or quasi-analytical solutions of the fractional sub-steps for the spatial transport and collisional terms. This approach is free from the statistical noise typical for the direct Monte Carlo methods. Interesting kinetic features are found for realistic engineering systems. The detailed consideration is given to a BGK term, though generalization to a Boltzmann collisional operator is also possible. Proof of the full-mass, momentum and energy-conservation is given in the chapter. Efficiency and accuracy are demonstrated on the two classical problems: shear wave damping and back-step flow.