Eddy Simulation Of Turbulent Flow Research Articles

Consistent subgrid scale modelling for lattice Boltzmann methods

AbstractThe lattice Boltzmann method has become a widely used tool for the numerical simulation of fluid flows and in particular of turbulent flows. In this frame the inclusion of subgrid scale closures is of crucial importance and is not completely understood from the theoretical point of view. Here, we propose a consistent way of introducing subgrid closures in the BGK Boltzmann equation for large eddy simulations of turbulent flows. Based on the Hermite expansion of the velocity distribution function, we construct a hierarchy of subgrid scale terms, which are similar to those obtained for the Navier–Stokes equations, and discuss their inclusion in the lattice Boltzmann method scheme. A link between our approach and the standard way on including eddy viscosity models in the lattice Boltzmann method is established. It is shown that the use of a single modified scalar relaxation time to account for subgrid viscosity effects is not consistent in the compressible case. Finally, we validate the approach in the weakly compressible case by simulating the time developing mixing layer and comparing with experimental results and direct numerical simulations.

Large Eddy Simulation for turbulent flows with critical regularization

In this paper, we establish the existence of a unique “regular” weak solution to the Large Eddy Simulation (LES) models of turbulence with critical regularization. We first consider the critical LES for the Navier–Stokes equations and we show that its solution converges to a solution of the Navier–Stokes equations as the averaging radii converge to zero. Then we extend the study to the critical LES for magnetohydrodynamic equations.

Residual‐based artificial viscosity for simulation of turbulent compressible flow using adaptive finite element methods

SUMMARYIn this paper, we present a finite element method with a residual‐based artificial viscosity for simulation of turbulent compressible flow, with adaptive mesh refinement based on a posteriori error estimation with sensitivity information from an associated dual problem. The artificial viscosity acts as a numerical stabilization, as shock capturing, and as turbulence capturing for large eddy simulation of turbulent flow. The adaptive method resolves parts of the flow indicated by the a posteriori error estimates but leaves shocks and turbulence under‐resolved in a large eddy simulation. The method is tested for examples in 2D and 3D and is validated against experimental data. Copyright © 2012 John Wiley & Sons, Ltd.

Large Eddy Simulation of Turbulent Flow in a T-Junction

A large eddy simulation at the conditions of experiments by Vattenfall [1] was performed in order to investigate the phenomenon of turbulent mixing affecting the thermal fatigue in a T-junction. In the present LES based on the dynamic Vreman model, mean velocity, turbulence intensity, and Reynolds shear stress profiles show good agreement with those measured in the Vattenfall experiment. With the present LES results verified, the characteristics of vortical structures in terms of turbulent mixing resulting in thermal fatigue was investigated. The energy spectra are shown to have a dominant frequency of around St = 0.5 agreeing with the value reported in experiments. On the other hand, the dominant frequency near the wall is different from that reported at the centerline (St ∼ 1), meaning that the thermal fatigue may not result from the wake structure, and is affected by the vortical structures existing near the wall. This result is consistent with one stated by Muramatsu [2] that the frequency characteristics near the wall are closely associated with arched vortices. In addition, the present LES results are used to provide useful insights in predicting this kind of flow using RANS computations.

RETRACTED: Large eddy simulation of turbulent flow downstream of a backward-facing step

Abstract large eddy simulation is used to predict turbulent flow in the separated and reattached flow regions downstream of a backward-facing step.Simulations were carried out at a Reynolds number of 28 000 (based on the step height and the upstream centreline velocity) with a channel expansion ratio of 1.25. Two subgrid-scale models were tested, namely the dynamic eddy-viscosity, and the dynamic Vreman model. Both models showed good overall agreement with available experimental data. It is conjectured that the peak in these fluctuations is caused by an impingement mechanism, in which large eddies, originating in the shear layer, impact the wall just upstream of the mean reattachment location.

Large Eddy Simulation of Turbulent Flow and Heat Transfer in a Ribbed Coolant Passage

Numerical simulations of hydrodynamic and thermally fully developed turbulent flow are presented for flow through a stationary duct with periodic array of inline transverse rib turbulators. The rib height to hydraulic diameter ratio (e/Dh) is 0.1 and the rib pitch to rib height ratio (P/e) is 10. The effect of secondary flow due to presence of rib turbulators on heat and mass transfer has been investigated. The present work reviews the use of a large eddy simulation (LES) turbulence model, known as shear‐improved Smagorinsky model (SISM), for predicting flow and heat transfer characteristics in the fully developed periodic flow region. The computations are performed for Reynolds number of 2,053 and the working fluid chosen to be air, the Prandtl number of which is 0.7. Instantaneous flow field, time‐mean, and turbulent quantities are reported together with heat transfer and a close match with experiments has been observed.

Three-Dimensional Time-Dependent Large Eddy Simulation of Turbulent Flows in an Inductively Coupled Thermal Plasma Torch With a Reaction Chamber

A 3-D time-dependent simulation of a laboratory-scale inductively coupled thermal plasma torch system has been carried out to investigate unsteady turbulent flow patterns, which may arise in the reaction chamber as a consequence of a sharp expansion of the gas at the torch outlet. A large eddy simulation model has been used to predict the instantaneous flow field without any time filtering, as done in the Reynolds averaged Navier-Stokes models (for example, κ-ε or Reynolds stress model).

Large eddy simulation of turbulent flow surrounding two simulated CANDU fuel bundles

Three-dimensional turbulent flow in one and a half simulated 43-element CANDU ® 1 1 A registered trade mark of Atomic Energy of Canada Ltd. (AECL). fuel bundle at the inlet of a fuel channel is solved using large eddy simulation. Wake generated after the endplates and the flow development in the inlet bundle are investigated based on the simulation results. Spatial distribution and frequency spectra of fluid force components are also examined. The simulation results are compared to experimental data available in the literature as well as the measurements conducted by the authors. The current investigation provides a basic understanding of the fluid excitation in a simulated 43-element fuel bundle. The results may be used in a flow-induced vibration analysis for fuel bundles.

Dynamic Global Model for Large Eddy Simulation in Complex Geometries

In the present study, the dynamic Vreman model based on the global equilibrium between the subgrid-scale dissipation and the viscous dissipation with a global model coefficient are applied to large eddy simulation of turbulent flow in complex geometries. Distributions of pressure, velocity and vorticity as well as some flow structure are gained, which is helpful to examine the performance of SGS model and understand the flow characters in complex geometries.

The rapid–slow decomposition of the subgrid flux in inhomogeneous scalar turbulence

In large eddy simulation of turbulent flow, because of the spatial filter, inhomogeneity and anisotropy affect the subgrid stress via the mean flow gradient. A method of evaluating the mean effects is to split the subgrid stress tensor into ‘rapid’ and ‘slow’ parts. This decomposition was introduced by Shao et al. (L. Shao, S. Sarkar, and C. Pantano, On the relationship between the mean flow and subgrid stresses in large eddy simulation of turbulent shear flows, Phys. Fluids 11 (1999), pp. 1229–1248) and applied to a priori tests of existing subgrid models in the case of a turbulent mixing layer. In the present work, the decomposition is extended to the case of a passive scalar in inhomogeneous turbulence. The contributions of rapid and slow subgrid scalar flux, both in the equations of scalar energy and scalar flux, are analyzed. A priori numerical tests are performed in the turbulent Couette flow with a mean scalar gradient. Results are then used to evaluate the performances of different popular subgrid scalar models. It is shown that the existing models can not well simulate the slow part and need to be improved in future works.

Large eddy simulations without explicit eddy viscosity models

The classical approach to performing large eddy simulations of turbulent flows is to employ in the governing equations subgrid scale models based on eddy viscosity concepts. The development of the similarity model about 30 years ago led to the realisation that subgrid scale models that do not use eddy viscosity concepts are possible and have many desirable properties. In this article, we review modelling approaches belonging to this category and discuss their advantages and the limitations.

A mixed large eddy simulation model based on the residual-based variational multiscale formulation

A mixed model based on the residual-based variational multiscale (RBVM) formulation is proposed for the large eddy simulation of turbulent flows. In this model the cross stresses are modeled by the RBVM term and the Reynolds stresses are represented by a Smagorinsky eddy viscosity. The mixed model is motivated by an a priori analysis of a turbulent flow field that indicates that the RBVM term correctly models the dissipation induced by the cross-stress term but underpredicts the contribution from the Reynolds stress term. The dynamic version of the mixed model is implemented in a Fourier-spectral code in order to predict the decay of incompressible, three-dimensional homogeneous isotropic turbulence. It is found that the mixed model yields better agreement with direct numerical simulation solution than the dynamic Smagorinsky and the RBVM models, which are its building blocks.

The influence of the non-resolved scales of thermal radiation in large eddy simulation of turbulent flows: A fundamental study

The filtered radiative transfer equation has been solved without subgrid-scale model and compared to a-priori estimations from direct numerical simulation of statistically stationary homogeneous isotropic turbulence. The importance of the large eddy simulation non-resolved scales on the thermal radiation is analysed in this academic case. The influence of the mean and variance of temperature of the system on the subgrid-scale correlations is studied. It is shown that the turbulence–radiation interaction (TRI) is greater for low-temperature flows, where the radiative transfer is lower. Moreover, the strongest subgrid-scale correlations, which are the temperature self-correlation and the absorption coefficient-temperature correlation, have opposite effects, which suggests that it is better to neglect both correlations, instead of modelling only one. Therefore, the assumption of neglecting the TRI in LES leads to good predictions. Three-dimensional filtering effects, as well as the grid influence on non-local quantities, such as the radiation intensity, are also analysed. These effects have a local influence, but are negligible in the tested cases.

Experimental study and large eddy simulation of turbulent flow around tube bundles composed of wavy and circular cylinders

This paper presents the results of an investigation on the effects of wavy cylindrical tubes in a staggered heat exchanger tube bundle. Experimental measurements and large eddy simulation (LES) technique were used to study the turbulent flow characteristics in a staggered tube bundle arrangement at a sub-critical Reynolds number of Re = 7500. The aim of this investigation is to compare the flow characteristics of a new configuration of cylindrical tubes with that of a similar arrangement which comprises purely circular cylinders. The first row of circular tubes is replaced by a row of wavy cylindrical tubes. The result of the experiment shows that the mean velocity distributions and turbulence intensity, obtained by the present LES method, are in good agreement with the Laser Doppler Anemometer (LDA) measurements. The wake patterns around the second row of cylinders become more well organized upon the introduction of wavy cylinders of optimal wavelength (λ/Dm = 6). The turbulent kinetic energy behind the first row of tubes is also reduced. The power density spectra of the vortex shedding in the tube bundle are evidently suppressed. As a result, the fluctuating forces of the tube bundles are weakened. However, the drag is not noticeably reduced by such modification.

A new dynamic one‐equation subgrid‐scale model for large eddy simulations

AbstractA new dynamic one‐equation subgrid‐scale (SGS) model is presented for large eddy simulations of turbulent flows. The new model, combining both advantages of the dynamic one‐equation SGS model (J. Appl. Mech. (ASME) 2006; 73:368–373) and the wall‐adapting local eddy viscosity model (Turbulence Combustion 1999; 62:183–200), has three prominent features: (1) one‐equation model, suitable for relatively coarse grid situations and simulation of high Reynolds number flows; (2) no test‐filtering operation is needed in determination of dynamic parameters, suitable for low‐order numerical discretization and unstructured or hybrid grid situations; and (3) treating the production of SGS kinetic energy and energy loss in grid‐scale (GS) portion due to SGS motion with different dynamic mechanisms, which is considered to be more reasonable than the local and instantaneous dynamic mechanism as adopted by most existing one‐equation dynamic SGS models. Computational examinations have been conducted for flows with Reynolds number ranging from 3000–70000, revealing that there are three promising aspects of the new SGS model: (1) adaptability for a wide range of flow regime; (2) less grid dependence; and (3) potential of wide applications in complex geometries and high Reynolds number turbulent flows. Copyright © 2009 John Wiley & Sons, Ltd.

Frequency-velocity-scalar filtered mass density function for large eddy simulation of turbulent flows

A methodology termed “frequency-velocity-scalar filtered mass density function” (FVS-FMDF) is developed for large eddy simulation (LES) of turbulent flows. The FVS-FMDF takes account of unresolved subgrid scales (SGSs) by considering the joint probability density function (PDF) of the frequency, the velocity, and the scalar fields. An exact transport equation is derived for the FVS-FMDF in which the effects of convection and chemical reaction are in closed forms. The unclosed terms in this equation are modeled in a fashion similar to PDF methods in Reynolds-averaged Navier–Stokes simulations. The FVS-FMDF transport is modeled via a set of stochastic differential equations (SDEs). The numerical solution procedure is based on a hybrid finite-difference (FD)/Monte Carlo (MC) method in which the LES filtered transport equations are solved by the FD, and the set of SDEs is solved by a Lagrangian MC procedure. LES of a temporally developing mixing layer is conducted via the FVS-FMDF, and the results are compared with those via the Smagorinsky SGS closure. All these results are also assessed by comparison with those obtained by direct numerical simulation (DNS). The FVS-FMDF predictions show favorable agreements with DNS data.

An algebraic variational multiscale–multigrid method for large eddy simulation of turbulent flow

An algebraic variational multiscale–multigrid method is proposed for large eddy simulation of turbulent flow. Level-transfer operators from plain aggregation algebraic multigrid methods are employed for scale separation. In contrast to earlier approaches based on geometric multigrid methods, this purely algebraic strategy for scale separation obviates any coarse discretization besides the basic one. Operators based on plain aggregation algebraic multigrid provide a projective scale separation, enabling an efficient implementation of the proposed method. The application of the algebraic variational multiscale–multigrid method to turbulent flow in a channel produces results notably closer to reference (direct numerical simulation) results than other state-of-the-art methods both for mean streamwise and root-mean-square velocities. For predicting highly sensitive components of the Reynolds-stress tensor in the context of turbulent recirculating flow in a lid-driven cavity, the algebraic variational multiscale–multigrid method also shows a remarkably good performance in predicting reference results from experiment and direct numerical simulation compared to other methods.

Self-Adaptive Upwinding for Large Eddy Simulation of Turbulent Flows on Unstructured Elements

A self-adaptive upwinding method for large eddy simulation is proposed to reduce the numerical dissipation of a low-order numerical scheme on unstructured elements. This method is used to extend an existing Reynolds-averaged Navier-Stokes code to a large eddy simulation code by adjusting the contribution of the upwinding term to the convective flux. This adjustment is essentially controlled by the intensity of the local wiggle and reduces the upwind contribution in the Roe-MUSCL scheme. First, the stability characteristic of the new scheme is studied using a channel flow stability test. It is essential to ensure that the proposed scheme is able to adjust upwinding in the presence of very high gradients and that it prohibits the divergence of the simulation. Second, the decaying isotropic turbulence is simulated to study the capability of the new scheme to generate the suitable decaying rate for the total kinetic energy and its influence over the slope of the energy spectrum at different computational times. Finally, the flow separation phenomenon over a NACA0025 profile is numerically investigated and results are compared with experimental data.

A new deconvolution method for large eddy simulation

In this paper we present and we briefly discuss a new way to derive approximate deconvolution subgrid models for the large eddy simulation of turbulent flows.

Analysis of the turbulence–radiation interactions for large eddy simulations of turbulent flows

In large eddy simulations (LES) of radiative heat transfer, the subgrid-scale (SGS) radiative emission and the SGS radiative absorption are two unclosed terms that arise after applying the filtering operation to the radiative transfer equation and which represent the effect of the SGS motions on the evolution of the resolved radiative heat flux. In the present work, a-priori tests based on direct numerical simulation of homogeneous isotropic turbulence have been carried out. It was found that the effect of the SGS radiative absorption may be neglected in LES, whereas the SGS radiative emission has to be modelled, particularly for engineering applications where the grids are generally coarse, and in flows with high turbulence intensities. Future works should be devoted to the development of SGS models for radiative transfer.