Numerical simulation of interface and plume formation in high-speed multiphase flow

Empirical and numerical simulation results of the launch of a liquid slug from a tube into the atmosphere at high velocity are presented. The slug, consisting of an aqueous salt solution, is propelled by the gaseous combustion products of a solid propellant, which are in direct contact with the liquid. The numerical simulation of the launch event is used to predict the deformation of the gas-liquid interface by calculating the liquid volume fraction, pressure, temperature, and velocity fields. Transient 2D and 3D simulations are performed with varying mesh densities and with varying refinement near wall boundaries. Turbulence is captured with the Reynolds Stress Model (RSM). The Volume of Fluid method is used to track the three components present in the system (air, saltwater, propellant gas), using separate Eulerian phases for each. Results of the 2D and 3D simulations are compared to each other and to empirical test data, which consists of transient pressure measurements inside the launch tube and high-speed video of the slug exit into the atmosphere. The numerical results predict the formation of both the slug and plume structures, as seen in the video of the launch. The results also capture interface deformation and Rayleigh-Taylor instability while the slug is accelerated through the launch tube.