Large-eddy simulations of a forced homogeneous isotropic turbulence with polymer additives

A statistical ensemble of large-eddy simulations (LES) is run simultaneously for the same flow. The information provided by the different large-scale velocity fields is used in an ensemble-averaged version of the dynamic model. This produces local model parameters that only depend on the statistical properties of the flow. An important property of the ensemble-averaged dynamic procedure is that it does not require any spatial averaging and can thus be used in fully inhomogeneous flows. Also, the ensemble of LES provides statistics of the large-scale velocity that can be used for building new models for the subgrid-scale stress tensor. The ensemble-averaged dynamic procedure has been implemented with various models for three flows: decaying isotropic turbulence, forced isotropic turbulence, and the time-developing plane wake. It is found that the results are almost independent of the number of LES in the statistical ensemble provided that the ensemble contains at least 16 realizations.

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Performance of the Finite Element and Finite Volume Methods for Large Eddy Simulation in Homogeneous Isotropic Turbulence

Journal of Scientific Research ◽

10.3329/jsr.v2i2.2582 ◽

2010 ◽

Vol 2 (2) ◽

pp. 237-249 ◽

Cited By ~ 1

Author(s):

M. A. Uddin ◽

C. Kato ◽

N. Oshima ◽

M. Tanahashi ◽

T. Miyauchi

Keyword(s):

Finite Element ◽

Large Eddy Simulation ◽

Finite Volume ◽

Isotropic Turbulence ◽

Finite Volume Methods ◽

Homogeneous Isotropic Turbulence ◽

Smagorinsky Model ◽

Eddy Simulation ◽

Large Eddy ◽

Better Than

Large eddy simulation (LES) in homogeneous isotropic turbulence is performed by using the Finite element method (FEM) and Finite volume vethod (FVM) and the results are compared to show the performance of FEM and FVM numerical solvers. The validation tests are done by using the standard Smagorinsky model (SSM) and dynamic Smagorinsky model (DSM) for subgrid-scale modeling. LES is performed on a uniformly distributed 643 grids and the Reynolds number is low enough that the computational grid is capable of resolving all the turbulence scales. The LES results are compared with those from direct numerical simulation (DNS) which is calculated by a spectral method in order to assess its spectral accuracy. It is shown that the performance of FEM results is better than FVM results in this simulation. It is also shown that DSM performs better than SSM for both FEM and FVM simulations and it gives good agreement with DNS results in terms of both spatial spectra and decay of the turbulence statistics. Visualization of second invariant, Q, in LES data for both FEM and FVM reveals the existence of distinct, coherent, and tube-like vortical structures somewhat similar to those found in instantaneous flow field computed by the DNS. Keywords: Large eddy simulation; Validation; Smagorinsky model; Dynamic Smagorinsky model; Tube-like vortical structure; Homogeneous isotropic turbulence. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.DOI: 10.3329/jsr.v2i2.2582 J. Sci. Res. 2 (2), 237-249 (2010)

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Comparative Study of the Grid-Scale and Subgrid-Scale Velocity Fields - A Priori Test

GANIT Journal of Bangladesh Mathematical Society ◽

10.3329/ganit.v30i0.8499 ◽

1970 ◽

Vol 30 ◽

pp. 19-31

Author(s):

M Ashraf Uddin ◽

M Matiar Rahman ◽

M Saiful Islam Mallik

Keyword(s):

Isotropic Turbulence ◽

A Priori ◽

Velocity Fields ◽

Subgrid Scale ◽

Homogeneous Isotropic Turbulence ◽

Eddy Simulation ◽

Large Eddy ◽

Spatial Spectra ◽

Sharp Cutoff ◽

Better Than

Generation of grid-scale (GS) and subgrid-scale (SGS) velocity fields is performed by direct filtering of DNS (Direct Numerical Simulation) data at a low Reynolds number in homogeneous isotropic turbulence in order to assess the spectral accuracy as well as the performance of filter functions for LES (Large Eddy Simulation). The filtering is performed using three classical filter functions: Gaussian, Tophat and Sharp cutoff filters and in all three cases the results are compared with three different filter widths for LES. Comparing the distributions of GS and SGS velocities, and the decay of turbulence with those from DNS fields through out the whole calculation we have found that among the three filter functions, the performance of Sharp cutoff filter is better than that of the other two filter functions in terms of both spatial spectra and the distribution of velocities. Furthermore, it is shown that the accuracy of the filtering approach does not depend only on the filter functions but also on the filter widths for LES. GANIT J. Bangladesh Math. Soc. (ISSN 1606-3694) 30 (2010) 19-31 DOI: http://dx.doi.org/10.3329/ganit.v30i0.8499

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Implicit Large-Eddy Simulation of Transition and Turbulence Decay

Volume 5: Multiphase Flow ◽

10.1115/ajkfluids2019-5451 ◽

2019 ◽

Author(s):

Fernando F. Grinstein

Keyword(s):

Large Eddy Simulation ◽

Isotropic Turbulence ◽

Navier Stokes ◽

Homogeneous Isotropic Turbulence ◽

Eddy Simulation ◽

Numerical Hydrodynamics ◽

Geometrical Complexity ◽

Turbulence Decay ◽

Large Eddy ◽

Implicit Large Eddy Simulation

Abstract Accurate predictions with quantifiable uncertainties are essential to many practical turbulent flow applications exhibiting extreme geometrical complexity and broad ranges of length and time scales. Under-resolved computer simulations are typically unavoidable in such applications, and implicit large-eddy simulation (ILES) often becomes the effective strategy. We focus on ILES initialized with well-characterized 2563 homogeneous isotropic turbulence datasets generated with direct numerical simulation (DNS). ILES is based on the LANL xRAGE code, and solutions are examined as function of resolution for 643, 1283, 2563, and 5123 grids. The ILES performance of new directionally-unsplit high-order numerical hydrodynamics algorithms in xRAGE is examined. Compared to the initial 2563 DNS, we find longer inertial subranges and higher turbulence Re for directional-split 2563 & 5123 xRAGE — attributed to having linked DNS (Navier-Stokes based) solutions to nominally inviscid (higher Re) Euler based ILES solutions. Alternatively — for fixed resolution, we find that significantly higher simulated turbulence Re can be achieved with unsplit (vs. split) discretizations.

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Regularization-based sub-grid scale (SGS) models for large eddy simulations (LES) of high-Redecaying isotropic turbulence

Journal of Turbulence ◽

10.1080/14685240902998215 ◽

2009 ◽

Vol 10 ◽

pp. N25 ◽

Cited By ~ 11

Author(s):

Abhilash J. Chandy ◽

Steven H. Frankel

Keyword(s):

Isotropic Turbulence ◽

Large Eddy Simulations ◽

Large Eddy

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Modulation of fluid temperature fluctuations by particles in turbulence

Journal of Fluid Mechanics ◽

10.1017/jfm.2021.939 ◽

2021 ◽

Vol 931 ◽

Author(s):

Izumi Saito ◽

Takeshi Watanabe ◽

Toshiyuki Gotoh

Keyword(s):

Isotropic Turbulence ◽

Thermal Relaxation ◽

Temperature Fluctuations ◽

Turnover Time ◽

Fluid Temperature ◽

Thermal Coupling ◽

Homogeneous Isotropic Turbulence ◽

Large Eddy ◽

Theoretical Predictions ◽

Momentum Coupling

Modulation of fluid temperature fluctuations by particles due to thermal interaction in homogeneous isotropic turbulence is studied. For simplicity, only thermal coupling between the fluid and particles is considered, and momentum coupling is neglected. Application of the statistical theory used in cloud turbulence research leads to the prediction that modulation of the intensity of fluid temperature fluctuations by particles is expressed as a function of the Damköhler number, which is defined as the ratio of the turbulence large-eddy turnover time to the fluid thermal relaxation time. Direct numerical simulations are conducted for two-way thermal coupling between the fluid temperature field and point particles in homogeneous isotropic turbulence. The simulation results are shown to agree well with the theoretical predictions.

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A Framework to Assess the Quality and Robustness of LES Codes

Volume 2: Fora ◽

10.1115/fedsm2006-98262 ◽

2006 ◽

Author(s):

J. Meyers ◽

P. Sagaut ◽

B. J. Geurts

Keyword(s):

Isotropic Turbulence ◽

Optimal Parameter ◽

Second Order ◽

Homogeneous Isotropic Turbulence ◽

Parameter Region ◽

Determine Parameter ◽

Multi Objective ◽

Eddy Simulation ◽

Large Eddy ◽

Order Scheme

We present a framework which can be used to rigorously assess and compare large-eddy simulation methods. We apply this to LES of homogeneous isotropic turbulence using a Smagorin-sky model and three different discretizations. By systematically varying the simulation resolution and the Smagorinsky coefficient, one can determine parameter regions for which one, two or multiple flow predictions are simultaneously predicted with approximately minimal error. To this end errors on the predicted longitudinal integral length scale, the resolved kinetic energy and the resolved enstrophy are considered. Parameter regions where all considered errors are simultaneously (nearly) minimal are entitled ‘multi-objective optimal’ parameter regions. Surprisingly, we find that a standard second-order method has a larger ‘multi-objective optimal’ parameter region than two considered fourth order methods. Moreover, the errors in the respective ‘multi-objective optimal’ regions are also lowest for the second-order scheme.

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