Large eddy simulations of turbulence in physical space analysis of spectral energy transfer

2008 ◽  
pp. 68-80
Author(s):  
J. P. Benqué ◽  
A. Hauguel ◽  
D. Laurence
Keyword(s):  
Energy Transfer ◽  
Physical Space ◽  
Large Eddy Simulations ◽  
Spectral Energy ◽  
Space Analysis ◽  
Large Eddy

Energy transfer in rotating turbulence

1997 ◽  
Vol 337 ◽  
pp. 303-332 ◽  
Author(s):  
CLAUDE CAMBON ◽  
N. N. MANSOUR ◽  
F. S. GODEFERD
Keyword(s):  
Energy Transfer ◽  
Rotation Axis ◽  
Physical Space ◽  
Nonlinear Effects ◽  
Spectral Energy ◽  
Rossby Number ◽  
Dimensional Manifold ◽  
Two Dimensional ◽  
Weakly Nonlinear ◽  
Plane Normal

The influence of rotation on the spectral energy transfer of homogeneous turbulence is investigated in this paper. Given the fact that linear dynamics, e.g. the inertial waves regime found in an RDT (rapid distortion theory) analysis, cannot affect a homogeneous isotropic turbulent flow, the study of nonlinear dynamics is of prime importance in the case of rotating flows. Previous theoretical (including both weakly nonlinear and EDQNM theories), experimental and DNS (direct numerical simulation) results are collected here and compared in order to give a self-consistent picture of the nonlinear effects of rotation on turbulence.The inhibition of the energy cascade, which is linked to a reduction of the dissipation rate, is shown to be related to a damping of the energy transfer due to rotation. A model for this effect is quantified by a model equation for the derivative-skewness factor, which only involves a micro-Rossby number Roω=ω′/(2Ω) – ratio of r.m.s. vorticity and background vorticity – as the relevant rotation parameter, in accordance with DNS and EDQNM results.In addition, anisotropy is shown also to develop through nonlinear interactions modified by rotation, in an intermediate range of Rossby numbers (RoL<1 and Roω>1), which is characterized by a macro-Rossby number RoL based on an integral lengthscale L and the micro-Rossby number previously defined. This anisotropy is mainly an angular drain of spectral energy which tends to concentrate energy in the wave-plane normal to the rotation axis, which is exactly both the slow and the two-dimensional manifold. In addition, a polarization of the energy distribution in this slow two-dimensional manifold enhances horizontal (normal to the rotation axis) velocity components, and underlies the anisotropic structure of the integral length-scales. Finally a generalized EDQNM (eddy damped quasi-normal Markovian) model is used to predict the underlying spectral transfer structure and all the subsequent developments of classic anisotropy indicators in physical space. The results from the model are compared to recent LES results and are shown to agree well. While the EDQNM2 model was developed to simulate ‘strong’ turbulence, it is shown that it has a strong formal analogy with recent weakly nonlinear approaches to wave turbulence.

Large-eddy simulations of convection initiation over heterogeneous, low terrain

2022 ◽  
Keyword(s):  
Kinetic Energy ◽  
Free Convection ◽  
Deep Convection ◽  
Physical Space ◽  
Peak Height ◽  
Spectral Shape ◽  
Large Eddy Simulations ◽  
Power Spectral ◽  
Large Eddy ◽  
Convection Initiation

Abstract Large-eddy simulations are conducted to investigate and physically interpret the impacts of heterogeneous, low terrain on deep-convection initiation (CI). The simulations are based on a case of shallow-to-deep convective transition over the Amazon River basin, and use idealized terrains with varying levels of ruggedness. The terrain is designed by specifying its power-spectral shape in wavenumber space, inverting to physical space assuming random phases for all wave modes, and scaling the terrain to have a peak height of 200 m. For the case in question, these modest terrain fields expedite CI by up to 2-3 h, largely due to the impacts of the terrain on the size of, and subcloud support for, incipient cumuli. Terrain-induced circulations enhance subcloud kinetic energy on the mesoscale, which is realized as wider and longer-lived subcloud circulations. When the updraft branches of these circulations breach the level of free convection, they initiate wider and more persistent cumuli that subsequently undergo less entrainment-induced cloud dilution and detrainment-induced mass loss. As a result, the clouds become more vigorous and penetrate deeper into the troposphere. Larger-scale terrains are more effective than smaller-scale terrains in promoting CI because they induce larger enhancements in both the width and the persistence of subcloud updrafts.

Assesment of Modeling and Discretization Error in Finite-Volume Large Eddy Simulations

2006 ◽  
Author(s):  
Adetokunbo A. Adedoyin ◽  
D. Keith Walters ◽  
Shanti Bhushan
Keyword(s):  
Turbulent Flows ◽  
Finite Volume ◽  
Isotropic Turbulence ◽  
Decay Rates ◽  
Large Eddy Simulations ◽  
Spectral Energy ◽  
Stress Model ◽  
Discretization Scheme ◽  
Large Eddy ◽  
Subgrid Stress

Large eddy simulations of turbulent flows are known to suffer from two separate error sources: the subgrid stress model and the numerical discretization scheme. In general, the two sources of error cannot be separately quantified for finite-difference/finite-volume CFD simulations. The motivation of this paper lies in the desire to determine optimum combinations of currently available subgrid stress models and numerical schemes for use in large eddy simulations of complex flows. Error assessments for large eddy simulation of turbulent fluid flow are presented. These assessments were carried out using pseudospectral simulation techniques in order to isolate finite-differencing and modeling errors by explicitly adding numerical derivative error terms to the simulations and analyzing their effect. Results from several combinations of subgrid stress model and spatial discretization scheme are presented. Simulations were performed for decaying isotropic turbulence on both 323 and 643 grids. Results were compared in terms of spectral energy distributions at succeeding time intervals. For verification, the pseudo-spectral results were compared to LES solutions obtained from a commercially available finite-volume flow solver (FLUENT), and comparisons were made in terms of energy decay rates, numerical versus subgrid stress dissipation levels, and computed energy spectra. The results highlight the interaction between subgrid stress model and discretization scheme. The results also indicate that certain combinations of model and numerical scheme may be more appropriate for finite-volume LES than others.

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