The Effect of a Dominant Initial Single Mode on the Kelvin–Helmholtz Instability Evolution: New Insights on Previous Experimental Results

Abstract

This paper brings new insights on an experiment, measuring the Kelvin–Helmholtz (KH) instability evolution, performed on the OMEGA60 laser facility. Experimental radiographs show that the initial seed perturbations in the experiment are of multimode spectrum with a dominant singlemode of 16 خ¼m wavelength. In singlemodedominated KH instability flows, the mixing zone (MZ) width saturates to a constant value comparable to the wavelength. However, the experimental MZ width at late times has exceeded 100 خ¼m, an order of magnitude larger. In this work, we use numerical simulations and a statistical model in order to investigate the vortex dynamics of the KH instability for the experimental initial spectrum. We conclude that the KH instability evolution in the experiment is dominated by multimode, vortexmerger dynamics, overcoming the dominant initial mode.