Influence of Initial Conditions on Turbulent Mixing in Shock Driven Richtmyer-Meshkov Flows

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Recent computational studies have shown that carefully designed initial conditions can be used to control late time turbulence and mixing in buoyancy-driven Rayleigh-Taylor (RT) as well as shock-driven Richtmyer-Meshkov (R-M) ∞ows. Such a dependence has not been conflrmed in experiments, which is important for Veriflcation and Validation (V&V) purposes. A systematic experimental study is carried out to understand the in∞uence of initial condition parameters, namely the amplitude ‐0 and wavenumber •0=2…/‚0 (where ‚0 is the wavelength) of perturbations, on R-M mixing and transition to turbulence. Initial conditions in the form of stable, single and multi mode membrane-free gas curtain of airSF6-air was used in our experiments. The density and velocity flelds for the difierent initial conflgurations were characterized using Planar Laser Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV) respectively. These initial conditions were subjected to a shock wave with Mach number M = 1.2 and the evolution of R-M instability after the incident shock and subsequent re-shock was obtained using simultaneous PLIF and PIV. A non-dimensional length scale deflned as · = •‐ was used to parametrically link the initial condition dependence to R-M mixing. Statistics such as dimensionless mixing widths, turbulent kinetic energy, turbulent Reynolds number, variances of velocity ∞uctuations were measured to quantify the amount of mixing. Some of these statistics were found to be in disagreement with the linear theory. The results also indicate a strong correlation between initial condition parameters and mixing at late times. These results present an opportunity to predict and \design late-time turbulence, with transformative impact on our understanding and prediction of Inertial Conflnement Fusion and general ∞uid mixing processes. The experimental results obtained are being compared with data from ongoing 3-D Implicit Large Eddy Simulation.