# Richtmyer-Meshkov mixing layer growth from localized perturbations

## TL;DR

This paper investigates the growth mechanisms of Richtmyer-Meshkov mixing layers originating from localized surface perturbations, revealing distinct turbulent structure formation and entrainment processes compared to uniform perturbations.

## Contribution

It introduces a novel analysis of RM mixing from localized features, highlighting different growth dynamics and vortex-driven entrainment mechanisms.

## Key findings

- Turbulent structures form into discrete packets separated from the surface.
- Material entrainment is dominated by laminar inward flow from smooth regions.
- Growth mechanisms differ significantly from those with uniform perturbations.

## Abstract

We study the growth of Richtmyer-Meshkov mixing layers from an initial surface with spatially localized perturbations. We use two symmetric forms of the initial patch, which allow simulation data to be averaged to generate a two-dimensional statistical representation of the three dimensional turbulent flow. We find that as the mixing layer grows, the turbulent structures tend to form into discrete packets separated from the surface, with material entrainment into them dominated by a laminar entrainment flow inward from the surrounding regions where the surface was originally smooth. The entrainment appears to be controlled by the propagation of vortex pairs which appear at the boundary of the region of initial perturbations. This suggests that the growth of RM mixing from isolated features, as may be found in manufactured Inertial Confinement Fusion capsules, has a rather different mechanism than the growth of an RM mixing layer when the perturbations are uniform. This may be a challenge for some existing engineering models.