Experimental study of shocked gas interfaces with visualized initial conditions

The Richtmyer-Meshkov instability is studied for strongly shocked fluid interfaces in the nonlinear regime. An introduction to the instability is presented which includes important historical information as well as the motivation for pursuing the current research. A literature survey is conducted that covers the most relevant and recent work in the field, experimental, theoretical and numerical. The experimental review concerns the facilities used to conduct the research, diagnostic techniques and results. Numerical hydrodynamic simulations are reviewed concerning computational techniques, initial conditions and comparisons with experimental data. New research is presented that covers the design, construction, operating parameters and diagnostics of the experimental facility—the Wisconsin Shock Tube Laboratory (WiSTL). The interface section is modified to provide a visualization capability for the initial condition for each Richtmyer-Meshkov experiment. A two dimensional initial condition for the Richtmyer-Meshkov experiments is prepared with a novel retractable plate with a sine wave perturbation. The plate initially separates the driven and test gases in the interface section, and upon retraction, a Rayleigh-Taylor unstable interface develops which provides the initial perturbation for the Richtmyer-Meshkov experiments. Five experimental campaigns are presented for two gas pairs: CO₂-air for shock strengths M = 1.41, 2.90, 3.08 and Ar-N₂ for M = 1.38 and 2.80. The experiments are simulated using a new hydrodynamic computer code. The computer code is two-dimensional and solves the unsteady compressible Euler equations using a Riemann solver. Experimental and numerical simulation results are compared with linear and nonlinear theories. The experimental results generally show more instability growth than either the simulation or theories predict, especially for the strongly shocked interface. A density freeze-out simulation for an Ar-N₂ interface, M = 3.352, is conducted and the interface does not experience an absence of growth but the unstable interface continues to grow into the nonlinear regime.