Numerical simulation of cold flow for initialization of gas-puff Z-pinches

Summary form only given. The design, development, and optimization of pulsed power machines utilizing Z-pinches of gases could be augmented by numerical simulation of gas-puffs to provide initial flow conditions of gas-puff nozzles. Gas-puff operation typically involves the expansion of a working gas such as argon from a reservoir at /spl sim/300 K, 1 atm through a hypersonic nozzle and into a low-pressure chamber where it is magnetically pinched. Navier-Stokes simulations of argon cold flow using a conventional, calorically-perfect gas model do not correlate well with experimental data. The simulations indicate highly supersaturated conditions are present in large regions of the flow, suggesting the presence of clusters that could significantly impact the mass distribution. To investigate the effects of clustering, an equilibrium model which approximates the saturated state as a thermally-perfect gas has been developed and implemented as an alternative to the calorically-perfect, gas model. Implementation of the model into the GASPv4 CFD code proved to be straightforward and is expected to be so for other CFD codes accommodating temperature-dependent gas properties. The saturated state model is described and results of simulations utilizing it are presented, demonstrating significant improvements in comparisons with experimental data.