Time-Resolved Measurements of Turbulent Mixing in Shock-Driven Variable-Density Flows

Abstract

Recent developments of burst-mode lasers and imaging systems have opened new realms of simultaneous diagnostics for velocity and density fields at a rate of 1 kHz–1 MHz. These enable the exploration of previously unimaginable shock-driven turbulent flow fields that are of significant importance to problems in high-energy density physics. The current work presents novel measurements using simultaneous measurements of velocity and scalar fields at 60 kHz to investigate Richtmyer-Meshkov instability (RMI) in a spatio-temporal approach. The evolution of scalar fields and the vorticity dynamics responsible for the same are shown, including the interaction of shock with the interface. This temporal information is used to validate two vorticity-deposition models commonly used for initiation of large scale simulations, and have been previously validated only via simulations or integral measures of circulation. Additionally, these measurements also enable tracking the evolution and mode merging of individual flow structures that were previously not possible owing to inherently random variations in the interface at the smallest scales. A temporal evolution of symmetric vortex merging and the induced mixing prevalent in these problems is presented, with implications for the vortex paradigms in accelerated inhomogenous flows.

Simultaneous measurements of kinetic and scalar energy spectrum time evolution in the Richtmyer–Meshkov instability upon reshock

“…Simultaneous high-speed measurements of reshocked RMI have been collected by Carter et al. (2019), where the analysis focused on the exploration of integral quantities. A comprehensive review of the state of the art of RMI studies is presented by Zhou (2017 a , b ).…”

“…Simulations have been performed, supporting a series of laser-driven experiments on the National Ignition Facility at Lawrence Livermore National Laboratory, that incorporate high energy density effects into the simulation of the RMI showing non-negligible effects on small-scale mixing by the increased energy transport via thermal electrons (Bender et al 2021). Simultaneous high-speed measurements of reshocked RMI have been collected by Carter et al (2019), where the analysis focused on the exploration of integral quantities. A comprehensive review of the state of the art of RMI studies is presented by Zhou (2017a,b).…”

Temporal evolution of scalar modes in Richtmyer–Meshkov instability of inclined interface using high-speed PIV and PLIF measurements at 60 kHz

“…With the availability of burst-mode lasers capable of high power at O(100 kHz) repetition rates, and high throughput imaging (>50 GPx s −1 ), extremely high-speed measurements of PIV and LIF are possible to study these shock-driven phenomena (Thurow et al 2012). Specifically for RMI, recent works of Carter et al (2019), Noble et al (2020aNoble et al ( , 2020b, Sewell et al (2021) have all implemented higher frame-rate PIV and PLIF. At 60 kHz, Carter et al (2019) present the fastest implementation of simultaneous PIV and qualitative PLIF to study RMI to date-the quantitative discussion of which will be done in the current work.…”

“…Specifically for RMI, recent works of Carter et al (2019), Noble et al (2020aNoble et al ( , 2020b, Sewell et al (2021) have all implemented higher frame-rate PIV and PLIF. At 60 kHz, Carter et al (2019) present the fastest implementation of simultaneous PIV and qualitative PLIF to study RMI to date-the quantitative discussion of which will be done in the current work. Qualitative discussion of the interface evolution and the vorticity deposition behavior from incident and reflected shocks were discussed.…”

“…The current work presents the quantitative discussion of the simultaneous PIV and PLIF measurements performed in Carter et al (2019) by performing the appropriate corrections. Given that the RMI of an inclined surface is a primarily vortexdominated flow (Zabusky 1999, Kokkinakis et al 2020, we aim to describe the influence of early time vortex roll-ups on the subsequent evolution of the scalar spatial modes.…”