Temporal decorrelations in compressible isotropic turbulence.

Area of Science:

• Fluid Dynamics
• Turbulence Research
• Computational Physics

Background:

• Understanding temporal decorrelations is crucial for analyzing turbulent flows.
• Compressible isotropic turbulence presents unique challenges due to density fluctuations.
• Existing models for temporal decorrelations may not fully capture dilatational effects.

Purpose of the Study:

• To investigate temporal decorrelations in compressible isotropic turbulence.
• To develop and validate models for both dilatational and solenoidal components.
• To extend the models to include the effect of a constant mean velocity.

Main Methods:

• Application of space-time correlation theory.
• Direct numerical simulation (DNS) of compressible isotropic turbulence.
• Development of a swept-wave model for dilatational components.
• Utilizing the classic random sweeping model for solenoidal components.

Main Results:

• The swept-wave model identifies random sweeping and wave propagation as key drivers of temporal decorrelations in dilatational fluctuations.
• DNS results validate the developed models, demonstrating a universal scaling collapse of normalized time correlations across different wavenumbers.
• The models successfully account for the behavior of temporal decorrelations in compressible isotropic turbulence.

Conclusions:

• Temporal decorrelations in compressible isotropic turbulence are governed by a combination of sweeping and wave propagation effects.
• The proposed swept-wave model provides a robust framework for understanding dilatational fluctuations.
• The findings offer improved theoretical and computational tools for turbulence research.