Bidirectional coupling of a line-by-line radiation and photon Monte Carlo transport solver with a kinetic plasma simulation framework

Thermal and chemical nonequilibrium effects are crucial for accurately predicting radiative properties and interpreting spectroscopic measurements. Computational Fluid Dynamics (CFD) methods, which typically simulate these flow fields, are based on Navier-Stokes equations. These equations are physically valid only within certain ranges of gas and plasma flows. Strong non-equilibrium effects cause high gradients in the flow field, and continuum assumptions break down in rarefied regions, increasing errors in Navier-Stokes-based CFD results and necessitating alternative modeling approaches. Particle-based methods such as Particle-in-Cell (PIC) and Direct Simulation Monte Carlo (DSMC) efficiently compute these types of flows, and provide detailed information about each flow species, including e.g. electronic excitation temperatures.

In this work, the open-source plasma suite PICLas is bidirectionally coupled with a radiation solver. A line-by-line method calculates radiative properties in the flow field, while a photon Monte Carlo approach calculates the radiative energy transfer. Models addressing the drawbacks of these methods (computational cost, statistical fluctuations, memory requirements) are implemented. The capabilities of the implemented methods are demonstrated using different test and application cases.