A lower bound on adiabatic heating of compressed turbulence for simulation and model validation

TL;DR

This paper establishes a theoretical lower bound on the adiabatic heating of compressed turbulence, providing a benchmark for simulation validation and insights into turbulence amplification in astrophysical contexts.

Contribution

It introduces a lower bound on turbulent velocity scaling during compression, linking dissipation effects to turbulence amplification in astrophysical systems.

Findings

The lower bound constrains turbulent velocity increase during compression.

Some simulations are more dissipative than the theoretical lower bound.

The method connects compressed turbulence with decaying turbulence dynamics.

Abstract

The energy in turbulent flow can be amplified by compression, when the compression occurs on a timescale shorter than the turbulent dissipation time. This mechanism may play a part in sustaining turbulence in various astrophysical systems, including molecular clouds. The amount of turbulent amplification depends on the net effect of the compressive forcing and turbulent dissipation. By giving an argument for a bound on this dissipation, we give a lower bound for the scaling of the turbulent velocity with compression ratio in compressed turbulence. That is, turbulence undergoing compression will be enhanced at least as much as the bound given here, subject to a set of caveats that will be outlined. Used as a validation check, this lower bound suggests that some simulations and models of compressing astrophysical turbulence are too dissipative. The technique used highlights the relationship between compressed turbulence and decaying turbulence.