Validation of Two Turbulence Models using High Speed Experimental Data from the Combined RM/RT Instability

High speed experimental data (PIV and Mie Scattering) are presented and used to validate two models commonly used in the simulation of variable density, compressible turbulent mixing. Though these models (Reynolds averaged Navier-Stokes and Large-Eddy Simulation) have previously been validated extensively on more canonical RM and RT flows, the present approach offers a new test case. The combined RM/RT instability, or the Blast Dirven Instability offers a compressible, combined instability in a complex geometry. The models are also validated on a notably uniform computational framework, by the same researchers who took the experimental data, leading to a tightly coupled experimental configuration with its model or "digital twin". The experimental setup of this divergent shock tube is shown along with samples of the high temporally resolved experimental data used for validation. For the model validation, first a non-mixing, 2D computational Euler model is optimized using a Gaussian process comparing simulation outputs to experimental data. This model then serves as the basis for both the RANS and the LES studies that make comparisons to the mixing layer data from the experiment. The RANS model is optimized using a similar Gaussian process. The LES model is validated against experimental data on an ensemble basis, using statistically characterized experimental initial conditions to seed random LES initial conditions. The resulting comparisons of experimental and simulation data for interface trajectory, mixing width, and turbulent kinetic energy are shown.