Turbulent mixing measurements in the Richtmyer-Meshkov instability

Abstract

The Richtmyer-Meshkov instability is experimentally investigated in a vertical shock tube using a new type of broadband initial condition imposed on an interface between a helium-acetone mixture and argon (A = 0.7). The initial condition is created by first setting up a gravitationally stable stagnation plane between the gases and then injecting the same two gases horizontally at the interface to create a shear layer. The perturbations along the shear layer create a statistically repeatable broadband initial condition. The interface is accelerated by a M = 1.6 planar shock wave, and the development of the ensuing turbulent mixing layer is investigated using planar laser induced fluorescence. By the latest experimental time, 2.1 ms after shock acceleration, the layer is shown to be fully turbulent, surpassing both turbulent transition criteria based on the Reynolds number and shear layer scale. Mixing structures are nearly isotropic by the latest time, as seen by the probability density function of gradient angles within the mixing layer. The scalar variance energy spectrum suggests a k−5/3 inertial range by the latest time and an exponential region at higher wavenumbers.

On the Kolmogorov inertial subrange developing from Richtmyer-Meshkov instability

“…Our data exhibit a Kolmogorov inertial range with a k −5/3 scaling followed by a region of exponential decay. The spectral results thus clearly support the findings of Weber et al 19 and are in excellent agreement with their experimental data up to the highest resolved wavenumbers.…”

“…The wide range of scaling laws observed in numerical simulations is subject to controversial discussions. However, recently published experimental data of Weber et al 19 suggest that a Kolmogorov inertial subrange followed by an exponential decay of the spectrum at higher wavenumbers exists. Hill et al 15 found a k −5/3 spectral range, however, they could not identify a region with an exponential decay beyond the inertial range.…”

“…Given the estimation ranges for η our fine-mesh simulation clearly qualifies as DNS. 26 Weber et al 19 give an estimate for the Batchelor scale λ B based on their experimental data, which is the smallest length scale in turbulent passive-scalar mixing. For Sc ≈ 1, the Kolmogorov scale is η ≈ λ B .…”

“…However, the fine grid exhibits more small scale features. In the experimental setup of Weber et al, 19 a broadband initial condition is formed by injecting a horizontal shear layer into a vertical shock tube. The broadband spectrum of modes that are present in the experiment can therefore only be described in a statistical sense.…”

Experimental Study of Turbulent Mixing in the Richtmyer-Meshkov Instability

“…The most significant temporal fluctuations occur at the bottom shear surface, where the light-gas mole fraction has a standard deviation of 0.2. This initial condition is characterized further in Weber et al [5]. The interface is accelerated by an incident shock wave of strength M = 1.57 ± 0.02 or M = 2.23 ± 0.02.…”