Temporal decorrelations in compressible isotropic turbulence

TL;DR

This paper investigates how temporal correlations decay in compressible isotropic turbulence using theoretical models and numerical simulations, revealing the dominant physical processes and validating the models with simulation data.

Contribution

It introduces a swept-wave model for dilatational components and extends the classic random sweeping model for solenoidal components, supported by DNS results.

Findings

Temporal decorrelations are dominated by random sweeping and wave propagation.

Normalized time correlation curves collapse across wavenumbers.

Models are extended to include constant mean velocity effects.

Abstract

Temporal decorrelations in compressible isotropic turbulence are studied using the space-time correlation theory and direct numerical simulation. A swept-wave model is developed for dilatational components while the classic random sweeping model is proposed for solenoidal components. The swept-wave model shows that the temporal decorrelations in dilatational fluctuations are dominated by two physical processes: random sweeping and wave propagation. These models are supported by the direct numerical simulation of compressible isotropic turbulence, in the sense of that all curves of normalized time correlations for different wavenumbers collapse into a single one using the normalized time separations. The swept-wave model is further extended to account for a constant mean velocity.