Ionization induced by fluid-solid interaction during hypervelocity impact

This paper presents a computational model to represent and investigate hypervelocity impacts that occur in an atmospheric environment, focusing on energy partitions and impact-induced ionization. The computational domain includes the projectile, the target, and the ambient gas. The physical model combines the compressible Navier-Stokes equations, a complete thermodynamic equation of state (EOS) for each material, and a non-ideal, multi-species Saha equation for ionization prediction. Material interfaces are tracked using an extended two- equation level set method, and the interfacial mass, momentum, and energy fluxes are computed by the FIVER (FInite Volume method with Exact multi-material Riemann problems) method. Using this model, the impact of tantalum on soda-lime glass (SLG) within argon gas is analyzed. Shock compression experiments are conducted to capture the thermodynamics of SLG under high pressure and temperature, yielding shock Hugoniot data up to 112 GPa and 5300 K. This data is used to calibrate a Noble-Abel stiffened gas EOS. Impact simulations are performed with initial velocity ranging from 3 km/s to 7 km/s. Time histories of the pressure, temperature, and plasma density fields are compared across the three materials. Less than 1% of the total impact energy is transferred to the ambient gas, yet its specific internal energy is of the same order of magnitude as that of the projectile and target. Argon gas exhibits higher temperature and plasma density than SLG and tantalum. The ionization of SLG is found to be highly selective, with the metallic elements contributing over 99.9% of the plasma's charged particles despite comprising less than 15% of the molar composition. In general, the results suggest that the plasma's density and energy depend on both impact velocity and the material combination, including the ambient gas. The plasma's composition further reflects the properties (e.g., ionization energies) of the chemical elements in each material.