Simulations of the non-linear thin shell instability

TL;DR

This study uses 3D simulations to analyze the non-linear thin shell instability in supersonic flows, confirming some analytic predictions and showing turbulence effects on the instability's growth.

Contribution

It provides new insights into how turbulence influences the growth of the NTSI, including suppression at certain Mach numbers, and validates analytic models with simulation data.

Findings

Growth speeds match Vishniac's predictions for monochromatic and white-noise perturbations.

Subsonic turbulence aligns with predictions only at short wavelengths.

Supersonic turbulence suppresses the NTSI.

Abstract

We use three-dimensional smoothed particle hydrodynamics simulations to study the non-linear thin shell instability (NTSI) in supersonic colliding flows. We show that for flows with monochromatic perturbations and for flows with white-noise perturbations, growth speeds approximate quite well to the analytic predictions of Vishniac (1994). For flows with subsonic turbulence, growth speeds match Vishniac's predictions only at short wavelengths where the turbulence is weaker. We find that supersonic turbulence, of a lower Mach number than the colliding flows, completely suppresses the NTSI. Our results provide a diagnostic for identifying the presence of the NTSI in colliding flows with turbulence.