Unstructured Large Eddy Simulation Research Articles

Large Eddy Simulation of Laminar and Turbulent Shock/Boundary Layer Interactions in a Transonic Passage

Abstract Shock/boundary layer interactions (SBLI) are a fundamental fluid mechanics problem relevant in a wide range of applications including transonic rotors in turbomachinery. This paper uses wall-resolved large eddy simulation (LES) to examine the interaction of normal shocks with laminar and turbulent inflow boundary layers in transonic flow. The calculations were performed using GENESIS, a high-order, unstructured LES solver. The geometry created for this study is a transonic passage with a convergent-divergent nozzle that expands the flow to the desired Mach number upstream of the shock and then introduces constant radius curvature to simulate local airfoil camber. The Mach numbers in the divergent section of the transonic passage simulate single stage commercial fan blades. The results predicted with the LES calculations show significant differences between laminar and turbulent SBLI in terms of shock structure, boundary layer separation and transition, and aerodynamic losses. For laminar flow into the shock, significant flow separation and low-frequency unsteadiness occur, while for turbulent flow into the shock, both the boundary layer loss and the low-frequency unsteadiness are reduced. The time period of the unsteadiness was hypothesized to align with the time it takes for turbulent structures to convect from the shock to the trailing edge and acoustic disturbances to travel back from the trailing edge to the shock, and this is supported by the LES results.

Euler–Lagrange numerical simulation of a kerosene droplet mist ignition in air using analytically reduced chemistry

High altitude relight is a critical aspect of the aeronautical engine certification and may be addressed with the numerical simulation of two-phase ignition. However, such configurations are stiff and combined with local evaporation may lead to numerical issues. This paper provides several methods to perform two-phase ignition simulations using analytically reduced chemistry in the context of unstructured large Eddy simulation and Euler–Lagrange formalism. Firstly, an exponential formulation combined with a local and dynamic sub-cycling of the stiff chemistry is demonstrated to allow stable integration at the flow time step. Secondly, a particle-bursting method is applied to limit the impact of stiffness induced by the Lagrangian point-source approach in fine meshes. These methods are then applied in the simulation of ignition of a mono-disperse, multi-component kerosene spray in air. The use of the analytically reduced chemistry model enables us to describe in detail the chemical structure of the flame kernel during its formation. Moreover, local increase of fuel concentration is observed as the ignition proceeds which has a large influence on the combustion processes and the flame kernel development.

Unstructured Large-Eddy Simulations of Rectangular Jet Screech: Assessment and Validation

High-fidelity large-eddy simulations (LESs) of a 4:1-aspect-ratio rectangular screeching jet are conducted at two underexpanded nozzle pressure ratios and nonheated flow conditions. To identify key numerical requirements for obtaining physically realistic jet screech in rectangular nozzles, a detailed assessment of mesh resolution and the Ffowcs Williams–Hawkings (FW-H) surface design is performed. Sufficiently fine grids are required in the jet shear layers and jet potential core to obtain accurate shock cell positions and jet spreading. To save computational costs, the FW-H sampling surface can be placed fairly close to the jet turbulence. In the region containing the jet initial shear layers and the supersonic core, the sampling surface can be placed near the 5–10% contour levels with respect to the maximum turbulent kinetic energy; and in regions further downstream, the sampling surface can be placed near the 20–25% contour levels. The LES results match closely with experimental measurements in terms of flow velocity and near- and far-field acoustics. The broadband noise spectra calculated by LESs agree very well with the experiment between and . For the stronger screech case, LESs are able to capture the screech tones within 2–5 dB as microphone measurements; whereas for the weaker screech case, the screech tones from LESs are weaker than measured values.

Azimuthal mode analysis of broadband shock-associated noise in an under-expanded axisymmetric jet

Broadband shock-associated noise (BBSAN) is a high frequency noise generated in imperfectly expanded jets from the interaction of turbulent structures and shock-cells. This paper presents an azimuthal mode analysis of BBSAN in the jet, near-field and far-field from an unstructured large-eddy simulation of a non-screeching supersonic under-expanded jet. The studied supersonic jet is issued from a round convergent nozzle with a perfectly expanded Mach number of 1.15 and Reynolds number based on the nozzle diameter of 1.25 × 106. Aerodynamic and far-field acoustic numerical results are validated against experiments. Pressure fluctuations represented in the frequency-wavenumber domain follow the neutral waves from a vortex-sheet model of an ideally expanded jet. The far-field pressure field is decomposed in azimuthal modes based on Fourier coefficients, showing three different regions: broadband behaviour of the mixing noise for downstream angles below 50° with the first modes containing most of the energy, BBSAN with similar amplitudes for the first 4 azimuthal modes at central angles between 50° and 130°, and distinct modes at upstream angles above 130°. A decomposition in negative/positive phase-velocity waves of the jet and near-field pressure field allows the identification of these characteristic modes. The complexity of the flow is illustrated with the analysis of the root-mean-square and spectral contents of the first 4 azimuthal modes. The modes exhibit peaks at different shock-cells and radial positions as well as depicting particular radiation patterns that depend on both the mode and frequency.

Accelerating unstructured large eddy simulation solver with GPU

PurposeAdopting large eddy simulation (LES) to simulate the complex flow in turbomachinery is appropriate to overcome the limitation of current Reynolds-Averaged Navier–Stokes modelling and it provides a deeper understanding of the complicated transitional and turbulent flow mechanism; however, the large computational cost limits its application in high Reynolds number flow. This study aims to develop a three-dimensional GPU-enabled parallel-unstructured solver to speed up the high-fidelity LES simulation.Design/methodology/approachCompared to the central processing units (CPUs), graphics processing units (GPUs) can provide higher computational speed. This work aims to develop a three-dimensional GPU-enabled parallel-unstructured solver to speed up the high-fidelity LES simulation. A set of low-dissipation schemes designed for unstructured mesh is implemented with compute unified device architecture programming model. Several key parameters affecting the performance of the GPU code are discussed and further speed-up can be obtained by analysing the underlying finite volume-based numerical scheme.FindingsThe results show that an acceleration ratio of approximately 84 (on a single GPU) for double precision algorithm can be achieved with this unstructured GPU code. The transitional flow inside a compressor is simulated and the computational efficiency has been improved greatly. The transition process is discussed and the role of K-H instability playing in the transition mechanism is verified.Practical/implicationsThe speed-up gained from GPU-enabled solver reaches 84 compared to original code running on CPU and the vast speed-up enables the fast-turnaround high-fidelity LES simulation.Originality/valueThe GPU-enabled flow solver is implemented and optimized according to the feature of finite volume scheme. The solving time is reduced remarkably and the detail structures including vortices are captured.

Isothermal and heated subsonic jet noise using large eddy simulations on unstructured grids

Jet noise remains the major contributor to airplane noise at take-off. In the past half-century of research, sound generation mechanisms in supersonic jets have been extensively characterized, while the sound sources in subsonic jets are still to be clearly identified. For the last two decades, Large Eddy Simulations (LES) have become a major tool for investigating jet noise sources due to their ability to capture detailed information in turbulent flows and their moderate cost that allows industrial applications. However, many challenges still arise when dealing with complex nozzle geometries and heating effects in the jet core. In this paper, subsonic jets with or without nozzle geometry at Mach number of 0.9 and moderately high Reynolds numbers ranging from 2 × 105 to 1 × 106 are computed using LES, providing a base of validation for different nozzle configurations and operating conditions. In this work, the high-order unstructured LES solver AVBP is combined with Ffowcs Williams and Hawkings’ acoustic analogy on unstructured grids. The vortex pairing phenomenon is evidenced without properly triggering the turbulence in the jet at the nozzle exit. Hence, a non-geometrical tripping, where the firsts prism layers of the mesh at the nozzle wall are removed, is proposed and shown to be a successful method for triggering proper turbulence development in shear layers for the cases with nozzle. Moreover, it is more easily implemented because it does not require any geometrical modifications and it generates more natural turbulence than previous methods, leading the path to actual industrial dual-stream configurations. Both isothermal and heated jet flow cases are performed and validated with existing experimental data in terms of aerodynamics and acoustics, which demonstrates the capacity of an unstructured LES solver to correctly simulate both cold and heated jet noise phenomena.

Unstructured Large-Eddy Simulations of Supersonic Jets

Experience gained from previous jet noise studies with the unstructured large-eddy simulation flow solver “Charles” is summarized and put to practice for the predictions of supersonic jets issued from a converging–diverging round nozzle. In this work, the nozzle geometry is explicitly included in the computational domain using an unstructured body-fitted mesh. Two different mesh topologies are investigated, with emphasis on grid isotropy in the acoustic source-containing region, either directly or through the use of adaptive refinement, with grid size ranging from 42 to control volumes. Three different operating conditions are considered: isothermal ideally expanded (fully expanded jet Mach number of , temperature of , and Reynolds number of ), heated ideally expanded (, , and ), and heated overexpanded (, , and ). Blind comparisons with the available experimental measurements carried out at the United Technologies Research Center for the same nozzle and operating conditions are presented. The results show good agreement for both the flow and sound fields. In particular, the spectra shape and levels are accurately captured in the simulations for both near-field and far-field noise. In these studies, sound radiation from the jet is computed using an efficient permeable formulation of the Ffowcs Williams–Hawkings equation in the frequency domain. Its parallel implementation is reviewed and parametric studies of the far-field noise predictions are presented. As an additional step toward best practices for jet aeroacoustics with unstructured large-eddy simulations, guidelines and suggestions for the mesh design, numerical setup, and acoustic postprocessing steps are discussed.

Large-eddy simulations of flow past a square cylinder using structured and unstructured grids

The flow past a square cylinder at Re=2.2×104 is analyzed by large-eddy simulation (LES) using the fine grids in order to represent details of near-cylinder flows. The accuracy of LES on structured and unstructured grids is assessed from the engineering viewpoint, compared with previous studies. The finite differencing method code with 4th order central scheme for the convective term is used for structured LES, while the open-source finite volume method code (OpenFOAM 2.3.0) with 1st–2nd order schemes is applied for unstructured LES. Typical schemes in OpenFOAM are tested, i.e., “LUST” (blending of linear and linear upwind schemes), “limitedLinear” (TVD) and “linearUpwind” (linear upwind). In this study, three effects are emphasized: numerical schemes for convective terms, meshing strategies, and spanwise resolution and length. On the whole, OpenFOAM can obtain fairly accurate prediction of the time-averaged and r.m.s quantities no matter which numerical scheme is used. “LUST” and “linearUpwind” are suggested. Meshing refinement in wake can be a solution to improve the far-wake velocity distribution and to overcome the earlier energy decay of turbulent motions in the inertial subrange caused by artificial dissipation. Different degrees of instantaneous flow reattachment near the trailing edges are found in the results obtained by OpenFOAM. Flow reattachment is closely associated with the roll-up of shear layer, and the flow topology between the shear layer and the side wall featured by the frontal and leeward secondary vortex. In this regard, the refinement of hexahedra cells near cylinder gives a best solution among all present cases tested compared with the previous DNS result. Generally the Kelvin–Helmholtz instability can be accurately predicted by OpenFOAM under the present numerical conditions. In addition, the spanwise resolution seems no big effect in predicted results when less than 0.05D. By contrast, the increase in spanwise length to 14D from 4D plays an important role in obtaining reasonable spanwise correlation of pressure and consequently the overall fluctuating lifts.

高層建物壁面に設置された鉛直フィン部材の風荷重評価

Recently, energy-efficient technologies are employed to buildings in terms of reduction of environmental burdens. Vertical fins on walls of tall building are environmentally-friendly components as sunshade louver. As these components are exposed to outer air, wind loads should be evaluated for wind resistant design of cladding. However, the fluctuating wind pressures or forces acting on vertical fins are generally difficult to predict with accuracy because of the reproducibility in wind tunnel experiments which require geometrically-accurate models and installations of measurement system. On the other hand, recent development of techniques on computational fluid dynamics (CFD) has enabled us to simulate the complicated flow such as the wind around buildings. Large Eddy Simulation (LES) is expected to be adopted as an effective tool to evaluate wind load for wind-resistant design of buildings. As numerical computations can overcome the difficulties of experimental prediction for complicated models of cladding and components, wind loads of vertical fins are thought to be evaluated accurately by LES. For numerical prediction of pressure fields around vertical fins by LES, unstructured grid systems are effective in terms of flexibility in generating the computational model. Present authors previously discussed the applicability of unstructured LES for prediction of the fluctuating wind pressures on building models (isolated square cylinder, two square cylinders and actual building model in a real urban district) by comparison with experiments. In this paper, the fluctuating wind forces acting on the vertical fins on walls of tall building are examined using unstructured LES. Especially, focusing on the size effects of fins, the pressure fluctuations and the flow fields are studied to evaluate wind loads for practical wind resistant design. First, the applicability of unstructured LES for wind force estimation of fins is validated by comparison with wind tunnel experiments. Here, the computation is carried out using the same geometry as the experimental model which has relatively larger fins than actual situation. Strong wind forces act on the fins placed at the corners of building and the computed force distributions coincide with experiments with accuracy. Next, the wind forces acting on the downscaled fins are computed to simulate the real situation. The flow fields and the wind force fluctuations are quite different from those of experimental (large-scaled fin) model. For the case of downscaled fins, the pressure fields around fins are dominantly influenced by the turbulence structures formed by the building scale. The scale effects on the wind load evaluation of cladding components, which can be examined by only numerical simulations, is clarified. Moreover, some cases for practical investigation are also computed (corner geometry and wind direction). As the overall trend, the maximum forces of fins at lower height become larger than other heights. In order to elucidate these phenomena, flow fields at the upwind region are visualized. The vertical flow promoted by the configuration of fins intensifies the horseshoe vortex in upwind region and the secondary vortex appears near the upwind wall on the ground level. As a conclusion of this study, for evaluation of design wind load of cladding components such as vertical fins, the scale effects should be considered for accurate prediction of pressure fluctuation. Unstructured LES is available to evaluate the wind loads of vertical fins on walls of buildings and effective to elucidate the flow mechanism on the complicated surfaces of buildings.

Large-Eddy Simulation of Bluff-Body Flame Using the Equilibrium Combustion Model

Flame stabilization is an important issue in practical applications of combustion systems. The bluff-body configuration is a common technique that stabilizes the flame by producing a strong recirculation zone downstream of the bluff body. Gas turbines provide a typical application of the bluff-body configuration. In this paper, a computational study of a bluff-body flame has been undertaken using an unstructured large-eddy simulation. The filtered Navier–Stokes equations are closed using a standard Smagorinsky model, and an equilibrium combustion model is employed for the chemistry calculation. All filtered scalar quantities are evaluated using a presumed probability density function based on a beta distribution function. It was found that accurate prediction of velocity profiles are strongly dependent upon the inflow conditions. It was also found that the equilibrium model for chemistry calculation does not capture well the dynamics of the reaction in the recirculation zone, where the diffusion timescales are very small. Based on this observation, a criterion was established for the implementation of the equilibrium model in terms of diffusion and chemical timescales. The diffusion timescales are inversely proportional to the scalar dissipation rate. It was found that the ratio of the diffusion timescale to the chemical timescale must be at least to obtain accurate results with the equilibrium model.

Noise Source Analysis of a Rod–Airfoil Configuration Using Unstructured Large-Eddy Simulation

The noise generated by a rod–airfoil configuration is investigated using unstructured Large-Eddy simulation coupled with a Ffowcs-Williams and Hawkings technique. The detailed experimental database and several numerical simulations available enable an extensive validation of the proposed methodology. Similar or improved results are obtained both in the near field (surface coefficient distributions and velocity profiles) and in the acoustic far field (power spectral densities obtained with both porous and solid surfaces, and directivities) compared with the best and most recent simulations. Dipolar noise radiation at the rod vortex-shedding frequency and its harmonics are found to be dominant. Some additional quadrupolar source contributions are seen at low and high frequencies. The rod is shown to have a significant contribution to the far-field noise at grazing angles. Constructive interferences occur normal to the rod–airfoil axis, whereas destructive interferences appear at grazing angles.

Unstructured large eddy simulations of heated supersonic twin jets

Unstructured large eddy simulations are performed with the compressible flow solver ”Charles” developed at Cascade Technologies, for heated supersonic over-expanded jets issued from a twin nozzle. The study focuses on the modeling of the internal flow and its effects on the flow-field in the jet plume and ultimately on the radiated noise. In this work, near-wall adaptive mesh refinement, synthetic inflow turbulence and wall modeling are used inside the nozzle. In addition to the converging-diverging nozzle geometry, the computational domain includes the Y-duct, S-ducts, and angle adapter upstream of the nozzles, to realistically reproduce the elements of the experimental configuration where the internal flow conditions and wall modeling can be expected to affect the external flow-field and sound-field predictions. Comparisons between the numerical predictions and experimental PIV and far-field noise measurements from NASA Glenn Research Center will be presented and discussed.

Large eddy simulation of soot evolution in an aircraft combustor

An integrated kinetics-based Large Eddy Simulation (LES) approach for soot evolution in turbulent reacting flows is applied to the simulation of a Pratt & Whitney aircraft gas turbine combustor, and the results are analyzed to provide insights into the complex interactions of the hydrodynamics, mixing, chemistry, and soot. The integrated approach includes detailed models for soot, combustion, and the unresolved interactions between soot, chemistry, and turbulence. The soot model is based on the Hybrid Method of Moments and detailed descriptions of soot aggregates and the various physical and chemical processes governing their evolution. The detailed kinetics of jet fuel oxidation and soot precursor formation is described with the Radiation Flamelet/Progress Variable model, which has been modified to account for the removal of soot precursors from the gas-phase. The unclosed filtered quantities in the soot and combustion models, such as source terms, are closed with a novel presumed subfilter PDF approach that accounts for the high subfilter spatial intermittency of soot. For the combustor simulation, the integrated approach is combined with a Lagrangian parcel method for the liquid spray and state-of-the-art unstructured LES technology for complex geometries. Two overall fuel-to-air ratios are simulated to evaluate the ability of the model to make not only absolute predictions but also quantitative predictions of trends. The Pratt & Whitney combustor is a Rich-Quench-Lean combustor in which combustion first occurs in a fuel-rich primary zone characterized by a large recirculation zone. Dilution air is then added downstream of the recirculation zone, and combustion continues in a fuel-lean secondary zone. The simulations show that large quantities of soot are formed in the fuel-rich recirculation zone, and, furthermore, the overall fuel-to-air ratio dictates both the dominant soot growth process and the location of maximum soot volume fraction. At the higher fuel-to-air ratio, the maximum soot volume fraction is found inside the recirculation zone; at the lower fuel-to-air ratio, turbulent fluctuations in the mixture fraction promote the oxidation of soot inside the recirculation zone and suppress the accumulation of a large soot volume fraction. Downstream, soot exits the combustor in intermittent fuel-rich pockets that are not mixed during the injection of dilution air and subsequent secondary fuel-lean combustion. At the higher fuel-to-air ratio, the frequency of these fuel-rich pockets is increased, leading to higher soot emissions from the combustor. Quantitatively, the soot emissions from the combustor are overpredicted by about 50%, which is a substantial improvement over previous works utilizing RANS to predict such emissions. In addition, the ratio between the two fuel-to-air ratios predicted by LES compares very favorably with the experimental measurements. Furthermore, soot growth is dominated by an acetylene-based pathway rather than an aromatic-based pathway, which is usually the dominant mechanism in nonpremixed flames. This finding is the result of the interactions between the hydrodynamics, mixing, chemistry, and soot in the recirculation zone and the resulting residence times of soot at various mixture fractions (compositions), which are not the same in this complex recirculating flow as in nonpremixed jet flames.

Effects of free-stream turbulence on high pressure turbine blade heat transfer predicted by structured and unstructured LES

Recent developments and demonstrations for the prediction of turbulent flows around blades point to Large Eddy Simulations (LES) as a very promising tool. Indeed and despite the fact that this numerical method still requires modeling and intense computing effort compared to Reynolds Average Navier–Stokes (RANS), this fully unsteady simulation technique provides valuable information on the turbulent flow otherwise inaccessible. Theoretical limits and scales of wall bounded flows are now well mastered in simple cases but complex industrial applications usually introduce unknowns and mechanisms that are difficult to apprehend beforehand especially with LES which is usually computationally intensive and bounded to code scalability, mesh quality, modeling performances and computer power. In this specific context, few studies directly address the use of fully structured versus unstructured, implicit versus explicit flow solvers and their respective impact for LES modeling of complex wall bounded flows. To partly address these important issues, two dedicated structured and unstructured computational solvers are applied and assessed by comparing the predictions of the heat transfer around the experimental high pressure turbine blade profile cascade of Arts et al. [6]. First, both LES predictions are compared to RANS modeling with a particular interest for the accuracy/cost ratio and improvement of the physical phenomena around the blade. LES’s are then detailed and further investigated to assess their ability to reproduce the inlet turbulence effect on heat transfer and the development of the transitioning boundary layer around the blade. Quantitative comparisons against experimental findings show excellent agreement especially on the pressure side of the profile. Detailed analysis of the flow predictions provided by both the structured and unstructured solvers underline the importance of long stream-wise streaky structures responsible for the augmentation of the heat transfer and leading to the transition of the suction-side boundary layer.

Thermo-Acoustic Stability of a Helicopter Gas Turbine Combustor Using Large Eddy Simulation

Compressible Large Eddy Simulation (LES) of turbulent reacting flows potentially offers a realistic representation of the physical phenomena involved in thermoacoustic instabilities. Coupled with Helmholtz solvers, which provide a mean of identification of the acoustic eigenmodes in complex geometries, that advanced numerical tool may provide a very powerful environment to assess the stability of real engine combustion chambers. The common use of a fully unstructured LES solver and a Helmholtz eigenmode tool proves here to be very useful to diagnose two operating points of a real gas turbine chamber which are known to operate with self-sustained oscillations. If the geometrical complexity and proper computational domain are chosen, the two thermo-acoustic instabilities are very well reproduced. Predictibility of LES for such problems is thus demonstrated provided that issues pertaining to the inlet acoustic impedances can be properly answered.

Unstructured Large Eddy Simulation of the passive control of the flow in a weapon bay

Abstract The control of cavity flows has been investigated by the means of Large Eddy Simulations. The computations have been carried out on unstructured meshes to assess the efficiency of two passive acoustic oscillation suppression devices: the rod-in-crossflow and the flat-top spoiler. Despite a sustained interest and many experiments, a clear explanation for observed reduction in the flow-induced structure load is still missing. This work explores different hypotheses: the modification of the mean field and its linear stability properties, a pure deflection effect of the separated shear layer, or scale coupling between the rod wake and the turbulent mixing layer over the cavity. The aim here is to enhance the experimental database and provide leads towards a better understanding of the phenomena. The selected test-case is a cavity of length/depth ratio equal to 5, at Mach and Reynolds number of M ∞ = 0.85 and Re L = 7 . 10 6 , respectively.

Computational visualization of unsteady flow around vehicles using high performance computing

One of the largest-scale unstructured Large Eddy Simulation (LES) of flow around a full-scale road vehicle is conducted on the Earth Simulator in Japan. The main objective of our study is to look into the validity of LES for the assessment of vehicle aerodynamics, especially in the context of its possibility for unsteady or transient aerodynamic forces. Firstly, the aerodynamic LES proposed is quantitatively validated on the ASMO simplified model by comparing the mean pressure distributions on the vehicle surface with those obtained by a conventional Reynolds-Averaged Navier–Stokes simulation (RANS) or a wind tunnel measurement. Then, the method is applied to the full-scale vehicle with complicated geometry to qualitatively investigate the capability of capturing organized flow structures around the vehicle. Finally, unsteady aerodynamic forces acting on the vehicle in transient yawing angle change are estimated and relationship between the flow structures and the transient aerodynamic forces is mentioned. As a result, it is demonstrated that LES will be a powerful tool for the vehicle aerodynamic assessment in the foreseeable future, because it can provide precious aerodynamic data which conventional wind tunnel tests or RANS simulations are difficult to provide.

Unstructured large-eddy simulation for vehicle-components aerodynamics: flow over an idealised car mirror

We present results of large-eddy numerical simulation (LES) of flow over an idealised car mirror using unstructured, cell-centred, colocated, finite volume solver. The 'mirror' consists of a wall mounted, backward facing semicylinder on which a hemisphere of diameter, two times larger was mounted. The considered Reynolds number of 330.000 corresponds to a realistic car velocity of 120 km/h. The simulation has been aimed at providing insight into the typical flow pattern around a car mirror, as well as for generating hydrodynamic inputs for computing noise generated by the mirror, and data for benchmarking industrial CFD for vehicle aerodynamics. The problem of specifying inflow conditions, which poses a serious challenge to LES, was overcome by simultaneous simulation of a segment of flow, upstream from the mirror, which was mapped in the spanwise direction to generate turbulence over the complete inflow cross section of the main flow domain. Because no experimental data are publicly available for this or similar configurations, the computations were performed for two numerical grids, a coarser with 500.000 and a finer with 1.000.000 cells. The results obtained with both grids agree well. Prior to LES of the mirror flow, the method was validated in LES of flow over a surface mounted cube in a matrix with different grids, as well as in some other flows, showing very good agreement with experiments.