Session 1P - Transport/Numerical Simulations.
POSTER session, Monday morning, November 11
Exhibit Hall - Concourse Level, Adam's Mark
We improve current methods of incorporating the effect of collisions in a particle-in-cell plasma simulation algorithm. Besides stochastically scattering particle velocities toward a Maxwellian with a Langevin pusher, we: linearly transform particle velocities and displacements each time step in order to conserve momentum and energy and exactly recover the correct spatial diffusion, (2) identify, and therefore discount, the contribution to the cell thermal velocity of correlations among velocity and spatial coordinates for particles within a cell, and (3) adjust particle weights in order to reduce noise. Improvement (1) allows us to take time steps larger than the collision time while improvement (2) helps us to self-consistently calculate the collision rate as a function of thermal velocity. In principle, and as demonstrated by illustrative calculations, these methods allow us to accurately reproduce the highly collisional (fluid) limit.