Improving LES with OpenFOAM by minimising numerical dissipation and use of explicit algebraic SGS stress model

Abstract

There is a rapidly growing interest in using general-purpose CFD codes based on second-order finite volume methods for Large-Eddy Simulation (LES) in a wide range of applications, and in many cases involving wall-bounded flows. However, such codes are strongly affected by numerical dissipation and the accuracy obtained for typical LES resolutions is often poor. In the present study, we approach the problem of improving the LES capability of such codes by reduction of the numerical dissipation and use of an anisotropycapturing subgrid-scale (SGS) stress model. The latter is of special importance for wall-resolved LES with resolutions where the SGS anisotropy can be substantial. Here we use the Explicit Algebraic (EA) SGS model [Marstorp L, Brethouwer G, Grundestam O, et al. Explicit algebraic subgrid stress models with application to rotating channel flow. J Fluid Mech. 2009;639:403-432], and comparisons are made for channel flow at friction Reynolds numbers up to 934 with the dynamic Smagorinsky model. The numerical dissipation is reduced by using an OpenFOAM based custom-built flow solver that modifies the Rhie and Chow interpolation and allows to control and minimise its effects without causing numerical instability (in viscous, fully turbulent flows). Different resolutions were used and large improvements of the LES accuracy were demonstrated for skin friction, mean velocity and other flow statistics by use of the new solver in combination with the EA SGS model. By reducing the numerical dissipation and using the EA SGS model the resolution requirements for wall-resolved LES can be significantly reduced.

A finite-size correction model for two-fluid large-eddy simulation of particle-laden boundary layer flow

“…In a recent publication, Montecchia et al. (2019) performed a sensitivity analysis to the CFL number (, 0.2 and 0.3) and the results did not show strong sensitivities.

Figure 3.Sketch of the geometry and boundary conditions of the numerical domain for the simulation of the clear water configuration and configuration GB from Kiger & Pan (2002).

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Transport and modeling of subgrid-scale turbulent kinetic energy in channel flows

“…(3). For example, the production term in both the SMM 33,40 and EASSM [44][45][46] yield Eq. ( 9), although the SGS stresses in their model involve a non-eddy-viscosity term that represents the anisotropy of the SGS turbulent field.…”

“…Further discussions on the SMM have been conducted in several studies. [37][38][39][40][41][42][43] As another non-eddyviscosity type model, the explicit algebraic subgrid stress model (EASSM) [44][45][46] provides better prediction than the dynamic Smagorinsky model (DSM) in coarse grid cases.…”

A symmetry-preserving second-order time-accurate PISO-based method

“…Castano et al [7] prescribed the velocity boundary conditions from the analytical Taylor-Green solution, which may partially mask possible energy losses. Montecchia et al [23] modified the velocity interpolation method of Rhie and Chow [30] by introducing a scaling factor which allows to control the amount of Rhie and Chow filtering. Thereby, they reduced the amount of numerical dissipation introduced by the Rhie and Chow interpolation method.…”

“…Thereby, they reduced the amount of numerical dissipation introduced by the Rhie and Chow interpolation method. Montecchia et al [23] performed explicit LES simulations of turbulent channel flows with this modified interpolation method. Substantial improvements were obtained by minimising the amount of numerical dissipation.…”