Large Eddy Simulation for Incompressible Flows

Sagaut, Pierre

doi:10.1007/978-3-662-04416-2

Cited by 918 publications

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“…In numerical modelling for street-scale problems, Britter & Hanna (2003) point out that computational studies typically produce reasonable qualitative results but the performance, when compared with laboratory or field experiments, is little better than that of simple operational models. Large-eddy simulation (LES) (Sagaut, 2001) is a promising tool for computing unsteady 3-dimensional flows at high Reynolds number or with complex geometry. An LES resolves only the large-scale fluid motions and models the subgrid-scale (SGS) motions through filtering the Navier-Stokes equations.…”

Section: Introductionmentioning

confidence: 99%

LES and RANS for Turbulent Flow over Arrays of Wall-Mounted Obstacles

Xie

Castro

2006

Flow Turbulence Combust

233

138

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Abstract. Large-eddy simulation (LES) has been applied to calculate the turbulent flow over staggered wall-mounted cubes and staggered random arrays of obstacles with area density 25%, at Reynolds numbers between 5 × 10 3 and 5 × 10 6 , based on the free stream velocity and the obstacle height. Re = 5 × 10 3 data were intensively validated against direct numerical simulation (DNS) results at the same Re and experimental data obtained in a boundary layer developing over an identical roughness and at a rather higher Re. The results collectively confirm that Reynolds number dependency is very weak, principally because the surface drag is predominantly form drag and the turbulence production process is at scales comparable to the roughness element sizes. LES is thus able to simulate turbulent flow over the urbanlike obstacles at high Re with grids that would be far too coarse for adequate computation of corresponding smooth-wall flows. Comparison between LES and steady Reynolds-averaged Navier-Stokes (RANS) results are included, emphasising that the latter are inadequate, especially within the canopy region.

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Section: Introductionmentioning

confidence: 99%

LES and RANS for Turbulent Flow over Arrays of Wall-Mounted Obstacles

Xie

Castro

2006

Flow Turbulence Combust

233

138

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“…Additionally, we can take the trace of τ equal to zero without loss of generality, because the trace can be included as part of the scalarp. Since turbulence is so far from being completely understood, there is a wide range of closure models, mostly based on heuristic, ad hoc arguments that cannot be derived from the NS-equations, see for example [5] and the references therein. The most commonly used closure model is given by…”

Section: Large Eddy Simulationmentioning

confidence: 99%

When does eddy viscosity damp subfilter scales sufficiently?

Verstappen

2011

Quality and Reliability of Large-Eddy Simulations II

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Large eddy simulation (LES) seeks to predict the dynamics of spatially filtered turbulent flows. The very essence is that the LES-solution contains only scales of size ≥ , where denotes some user-chosen length scale. This property enables us to perform a LES when it is not feasible to compute the full, turbulent solution of the Navier-Stokes equations. Therefore, in case the large eddy simulation is based on an eddy viscosity model we determine the eddy viscosity such that any scales of size < are dynamically insignificant. In this paper, we address the following two questions: how much eddy diffusion is needed to (a) balance the production of scales of size smaller than ; and (b) damp any disturbances having a scale of size smaller than initially. From this we deduce that the eddy viscosity ν e has to depend on the invariants q = 1 2 tr(S 2 ) and r = − 1 3 tr(S 3 ) of the (filtered) strain rate tensor S. The simplest model is then given by ν e = 3 2 ( /π) 2 |r|/q. This model is successfully tested for a turbulent channel flow (Re τ = 590).

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“…The large-scale component is obtained by an application of a filter operator. In practice, this operator is a convolution integral of the form ω(x, t) = R 2 G Δ (|x − y|) ω(y, t) dy, where x = (x, y) T is the space coordinate, t denotes the time, and G Δ is the filter such as volume-average box-filter; see for example [23].…”

Section: Equations Of Turbulent Flow and Heat Transfermentioning

confidence: 99%

“…Introduction. The large-eddy simulation (LES) equations for incompressible thermal flows are obtained by applying a spatial filtering to the Navier-Stokes equations subject to the Boussinesq approximation; see [5,4,17,23,16,12] and the references therein. However, this procedure introduces a term called a subgrid stress tensor which needs to be modelled.…”

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confidence: 99%

A Galerkin-Characteristic Method for Large-Eddy Simulation of Turbulent Flow and Heat Transfer

El‐Amrani¹,

Seaı̈d²

2008

SIAM J. Sci. Comput.

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract. This work aims at the development of a nonoscillatory Galerkin-characteristic method for large-eddy simulation of turbulent flow and heat transfer. The method is based on combining the modified method of characteristics with a Galerkin finite element discretization of the incompressible Navier-Stokes/Boussinesq equations in primitive variables. It can be interpreted as a fractional step technique where the convective part and the Stokes/Boussinesq part are treated separately. A limiting procedure is implemented for the reconstruction of numerical solutions at the departure points. The main feature of the proposed Galerkin-characteristic method is that, due to the Lagrangian treatment of convection, the standard Courant-Friedrichs-Levy condition is relaxed, and the time truncation errors are reduced in the Stokes/Boussinesq part. To solve the generalized Stokes/Boussinesq problem we implement a conjugate gradient algorithm. This method avoids projection techniques and does not require any special correction for the pressure. We verify the method for an advection-diffusion equation with a known analytical solution and for the benchmark problem of mixed convection flow in a squared cavity. We also present numerical results for a problem of heat transport in the Strait of Gibraltar. The Galerkin-characteristic method has been found to be feasible and satisfactory.Key words. Galerkin-characteristic method, large-eddy simulation, heat transfer, finite element method, mixed convection, sea-surface temperature AMS subject classifications. 76F35, 74S05, 65M25DOI. 10.1137/080720711 1. Introduction. The large-eddy simulation (LES) equations for incompressible thermal flows are obtained by applying a spatial filtering to the Navier-Stokes equations subject to the Boussinesq approximation; see [5,4,17,23,16,12] and the references therein. However, this procedure introduces a term called a subgrid stress tensor which needs to be modelled. This term has to be seen as the interaction between the large and small scales in the system. In the current study, we will concentrate on a subgrid problem based on the Smagorinsky model [27]. The LES is normally performed on grids that are just fine enough to resolve the large flow scales, and numerical errors on such grids can have large effects on the simulation results. Although in the literature (see [12] and references therein) many numerical schemes have been presented, it is still not clear what the effect of the numerical and modelling errors in...

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Large Eddy Simulation for Incompressible Flows

Cited by 918 publications

References 0 publications

LES and RANS for Turbulent Flow over Arrays of Wall-Mounted Obstacles

LES and RANS for Turbulent Flow over Arrays of Wall-Mounted Obstacles

When does eddy viscosity damp subfilter scales sufficiently?

A Galerkin-Characteristic Method for Large-Eddy Simulation of Turbulent Flow and Heat Transfer

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