Advances in NIMROD Modeling of the HIT-SI Experiment

Previous two-fluid simulations of the HIT-SI experiment using the NIMROD code at low injector frequencies have served as a launching point for modeling of both pressure effects related to Steady Inductive Helicity Injection (SIHI) and the new HIT-SI3 injector configuration. Results from the end of HIT-SI operation have encouraged the inclusion of pressure effects in NIMROD modeling. Previous calculations using NIMROD assumed uniform temperature and density profiles, producing good agreement with low injector frequency operations ($f_{inj}<\frac{v_{th}}{a}$) but poor agreement at high injector frequencies ($f_{inj}>\frac{v_{th}}{a}$). Experimental observations at these higher frequencies give evidence of pressure driven activity, as well as a higher volume averaged $\beta$. The full anisotropic Braginskii thermal conduction model has been applied in NIMROD calculations of HIT-SI and shows improvement in qualitative agreement at high injector frequencies, while maintaining results at low frequencies. In addition, modeling of the new 3-injector configuration of HIT-SI3 will serve as a source of validation of the model.