Title: Mixing transition in a shocked variable-density flow

Abstract

We measure two-dimensional velocity and density fluctuations in a shock-driven heavy gas curtain for three different incident Mach numbers (M = 1.21, 1.36, and 1.50) and a fixed initial perturbation. We study the time evolution of the velocity and density fields and observe two different mixing transitions in this unsteady flow. The first transition is caused by small-scale mixing in vortex cores, while the second transition is related to increased homogenization across the mixing layer and a drive towards isotropy. By measuring the anisotropy of the velocity fluctuations and the evolution of the turbulent kinetic energy, we are able to assess the anisotropy of the flow. For the first time in Richtmyer-Meshkov (RM) flows, we measure and compare turbulent length scales derived from both the density and velocity field measurements, and we find ratios of Liepmann-Taylor to inner-viscous scales (λ_L/λ_v) that are inconsistent with those found using Reynolds number scaling based on circulation, Re_Γ, or based on turbulent kinetic energy, Re_K. At late times, Re_K better reflects the decay of the mixing field than Reynolds numbers that are based upon mixing width or circulation. We also estimate the time evolution of dissipation and Kolmogorov scales for the first time inmore » RM flows. When we estimate the Taylor microscale (λ_T) for our experiments using both density and velocity, the density microscale agrees well with with the relationship λ_T = √10δRe-^1/2 where Re = ReK and δ is the mixing layer width, but the velocity-based Taylor microscale follows a new scaling of λ_T = 10δRe^-1/2.« less

Authors:

Orlicz, G. C. ^[1]; Balasubramanian, Sridhar ^[2]; Vorobieff, P. ^[3]; Prestridge, K. P.  ^[1]

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+ Show Author Affiliations

1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Indian Inst. of Technology (IIT), Mumbai (India)
3. Univ. of New Mexico, Albuquerque, NM (United States)

Publication Date:

Mon Nov 16 00:00:00 EST 2015

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1492592

Report Number(s):

LA-UR-15-22836
Journal ID: ISSN 1070-6631; PHFLE6

Grant/Contract Number:  

89233218CNA000001

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Fluids

Additional Journal Information:

Journal Volume: 27; Journal Issue: 11; Journal ID: ISSN 1070-6631

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; Richtmyer-Meshkov; mixing; turbulence