Hybrid LES — Review and assessment

Abstract

Abstract. In the late eighties and up to the beginning of nineties computation of turbulent flows is mostly dominated by RANS (Reynolds Averaged Navier-Stokes Simulation) type modelling. During the last few years URANS (Unsteady RANS) and LES (Large Eddy Simulation) type of approaches have been attempted with some success. Yet, there have been many difficulties when LES is applied to practical engineering problems and to high Reynolds number flows as energy dissipating eddies become really small and mesh resolution required for a reasonably resolved LES approaches that of DNS (Direct Numerical Simulation). An alternative solution suggested was to combine RANS and LES, which in general referred to as Hybrid LES. There have been many proposals for combining RANS and LES in different ways. In this article, some of the issues involved in performing hybrid LES reported in the recent literature is briefly reviewed.

Assessment of the LES-WALE and Zonal-DES Turbulence Models in Simulation of the Flow Structures around the Finite Circular Cylinder

“…For example, explicit specification of interface location is obviously not a desirable one. The location should be automatically choose based on the local grid information without imposing further limitation on grid in other directions Vengadesan et al (2007). For fine grids, the switch from RANS to LES can take place somewhere inside the boundary layer and produce a premature grid-induced separation Menter et al (2004).…”

A Delayed Detached Eddy Simulation Model for the Simulation of Complex Turbulent Flow

“…An accuracy LES should solve all turbulence scales in the flow, including the majority of turbulent kinetic energy and Reynolds shear stress in the Local area (Vengadesan and Nithiarasu 2007). In LES simulations, the scales in the turbulence spectra that are approximately proportional to the wall separation are very tiny in the wall boundary layer and hence demand an overly high resolution, almost as high as direct numerical simulation (DNS).…”

Study of Interference Effects on Wind Turbine Structures

“…The modeling of Atmospheric Boundary Layer (ABL), as well as the turbulence in the flow domain, is vital to maintain the accuracy of the simulation models. In this study, a User Defined Function (UDF) is employed for generating the ABL [ (Tamura, 2015)] and Large Eddy Simulation (LES) methods [ (Vengadesan & Nithiarasu, 2007), (Tamura, 2009)] are used to model the turbulence [ (Kim, et al, 2011)]. During post processing, the value of pressure coefficient (C p ) is extracted at a specific height of the structure and interference factors at this height is computed.…”