Indirect validation of plasma viscosity models via the observation of the transition to turbulence*

Turbulence is a ubiquitous phenomenon in neutral fluids. In contrast, turbulence within collisional plasmas -- which are subject to strong transport effects (which are anisotropic in the presence of strong magnetic fields), and the possibility of electromagnetic field generation (e.g., via the Biermann battery mechanism) – may differ markedly from its neutral counterpart. In fact, 2-D/3-D xRAGE simulations of turbulence produced by a plasma flowing through a grid indicate that the appearance of turbulent eddies is strongly dependent upon the plasma viscosity coefficient – owing largely to its T^5/2 dependence on temperature. To further elucidate plasma "grid turbulence," we have launched an experimental campaign on the Plasma Liner Experiment (PLX) platform at LANL. Employing a modified PLX gun setup, we aim to characterize the grid turbulence produced by a non-magnetized plasma jet interacting with a solid grid. By carefully controlling the initial plasma conditions, thereby tuning the plasma viscosity coefficient, we seek to observe the transition of the plasma from laminar-like flows to developed turbulence. As a side benefit, correspondence between the experimental results and xRAGE modeling would provide an indirect validation of the code’s underlying plasma viscosity model. Here, we detail a simple analytical model – verified by comparisons with resistive MHD FLAG simulations – which roughly predicts the pre-jet plasma density, temperature, and flow velocity. Finally, we present preliminary PLX results and simulation comparisons.