Vorticity, backscatter and counter-gradient transport predictions using two-level simulation of turbulent flows

ABSTRACT

The two-level simulation (TLS) method evolves both the large-and the small-scale fields in a two-scale approach and has shown good predictive capabilities in both isotropic and wall-bounded high Reynolds number (Re) turbulent flows in the past. Sensitivity and ability of this modelling approach to predict fundamental features (such as backscatter, counter-gradient turbulent transport, small-scale vorticity, etc.) seen in high Re turbulent flows is assessed here by using two direct numerical simulation (DNS) datasets corresponding to a forced isotropic turbulence at Taylor’s microscale-based Reynolds number Re_λ ≈ 433 and a fully developed turbulent flow in a periodic channel at friction Reynolds number Re_τ ≈ 1000. It is shown that TLS captures the dynamics of local co-/counter-gradient transport and backscatter at the requisite scales of interest. These observations are further confirmed through a posteriori investigation of the flow in a periodic channel at Re_τ = 2000. The results reveal that the TLS method can capture both the large- and the small-scale flow physics in a consistent manner, and at a reduced overall cost when compared to the estimated DNS or wall-resolved LES cost.

KEYWORDS:

• Two-level simulation
• large eddy simulation
• vorticity
• turbulent transport
• backscatter

Acknowledgements

This work was supported by the Office of Naval Research N000141612577. The computation time provided by the DOD HPC center at Navy DSRC is highly appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Office of Naval Research [grant number N000141612577].