Lattice eddy simulation of turbulent flows

TL;DR

This paper introduces the Lattice Eddy Simulation (LAES) method, a novel turbulence modeling approach that uses a constant empirical coefficient and aligns with Kolmogorov's theory, achieving accurate results on coarse meshes.

Contribution

LAES is a new turbulence simulation method that simplifies sub-grid modeling with a constant coefficient, matching the accuracy of more complex models.

Findings

LAES accurately predicts turbulent channel flows at various Reynolds numbers.

LAES performs as well as the dynamic LES model on coarse meshes.

LAES supports Kolmogorov's theory of self-similarity in turbulence.

Abstract

Kolmogorov's (1941) theory of self-similarity implies the universality of small-scale eddies, and holds promise for a universal sub-grid scale model for large eddy simulation. The fact is the empirical coefficient of a typical sub-grid scale model varies from 0.1 to 0.2 in free turbulence and damps gradually to zero approaching the walls. This work has developed a Lattice Eddy Simulation method (LAES), in which the sole empirical coefficient is constant (Cs=0.08). LAES assumes the fluid properties are stored in the nodes of a typical CFD mesh, treats the nodes as lattices and makes analysis on one specific lattice, i. To be specific, LAES express the domain derivative on that lattice with the influence of nearby lattices. The lattices right next to i, which is named as i+, "collide" with i, imposing convective effects on i. The lattices right next to i+, which is named as i++, impose convective effects on i+ and indirectly influence i. The influence is actually turbulent diffusion. The derived governing equations of LAES look like the Navier-Stokes equations and reduce to filtered Naiver-Stokes equations with the Smagorinsky sub-grid scale model (Smagorinsky 1963) on meshes with isotropic cells. LAES yields accurate predictions of turbulent channel flows at Re=180, 395, and 590 on very coarse meshes and LAES with a constant Cs perform as well as the dynamic LES model (Germano et al. 1991) does. Thus, this work has provided strong evidence for Kolmogorov's theory of self-similarity.