Large eddy simulation for aerodynamics: status and perspectives

2009 ◽  
Vol 367 (1899) ◽  
pp. 2849-2860 ◽  
Author(s):  
Pierre Sagaut ◽  
Sébastien Deck
Keyword(s):  
Large Eddy Simulation ◽  
Computational Cost ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Error Quantification ◽  
Geometrical Complexity ◽  
First Case ◽  
Large Eddy ◽  
First Results

The present paper provides an up-to-date survey of the use of large eddy simulation (LES) and sequels for engineering applications related to aerodynamics. Most recent landmark achievements are presented. Two categories of problem may be distinguished whether the location of separation is triggered by the geometry or not. In the first case, LES can be considered as a mature technique and recent hybrid Reynolds-averaged Navier–Stokes (RANS)–LES methods do not allow for a significant increase in terms of geometrical complexity and/or Reynolds number with respect to classical LES. When attached boundary layers have a significant impact on the global flow dynamics, the use of hybrid RANS–LES remains the principal strategy to reduce computational cost compared to LES. Another striking observation is that the level of validation is most of the time restricted to time-averaged global quantities, a detailed analysis of the flow unsteadiness being missing. Therefore, a clear need for detailed validation in the near future is identified. To this end, new issues, such as uncertainty and error quantification and modelling, will be of major importance. First results dealing with uncertainty modelling in unsteady turbulent flow simulation are presented.

Implicit Large-Eddy Simulation of Transition and Turbulence Decay

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.

scholarly journals Comparison of dealiasing schemes in large-eddy simulation of neutrally stratified atmospheric flows

2018 ◽  
Vol 11 (10) ◽  
pp. 4069-4084 ◽  
Author(s):  
Fabien Margairaz ◽  
Marco G. Giometto ◽  
Marc B. Parlange ◽  
Marc Calaf
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Computational Cost ◽  
Navier Stokes ◽  
Partial Sums ◽  
Simulation Code ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Layer Flow ◽  
Neutrally Stratified

Abstract. Aliasing errors arise in the multiplication of partial sums, such as those encountered when numerically solving the Navier–Stokes equations, and can be detrimental to the accuracy of a numerical solution. In this work, a performance and cost analysis is proposed for widely used dealiasing schemes in large-eddy simulation, focusing on a neutrally stratified, pressure-driven atmospheric boundary-layer flow. Specifically, the exact 3∕2 rule, the Fourier truncation method, and a high-order Fourier smoothing method are intercompared. Tests are performed within a newly developed mixed pseudo-spectral finite differences large-eddy simulation code, parallelized using a two-dimensional pencil decomposition. A series of simulations are performed at varying resolution, and key flow statistics are intercompared among the considered runs and dealiasing schemes. The three dealiasing methods compare well in terms of first- and second-order statistics for the considered cases, with modest local departures that decrease as the grid stencil is reduced. Computed velocity spectra using the 3∕2 rule and the FS method are in good agreement, whereas the FT method yields a spurious energy redistribution across wavenumbers that compromises both the energy-containing and inertial sublayer trends. The main advantage of the FS and FT methods when compared to the 3∕2 rule is a notable reduction in computational cost, with larger savings as the resolution is increased (15 % for a resolution of 1283, up to a theoretical 30 % for a resolution of 20483).

scholarly journals Large eddy simulation of flow around semi-conical piers vertically mounted on the bed

2021 ◽  
Author(s):  
Yasin Aghaee-Shalmani ◽  
Habib Hakimzadeh
Keyword(s):  
Large Eddy Simulation ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Flow Structures ◽  
Shear Stresses ◽  
Eddy Simulation ◽  
Large Eddy

Abstract In this paper, details, and results of three-dimensional numerical modeling of flow around the semi-conical piers vertically mounted on the bed in a channel, are presented. For flow simulation, 3-D Navier-Stokes equations are solved numerically using the finite volume method and large eddy simulation (LES). In this study, the semi-conical piers with different side slope angles are tested, and the flow around them is compared with the cylindrical reference pier. Flow structures, vortex shedding behind piers, horseshoe vortices, instantaneous and time-averaged flow structures are presented and discussed. Numerical model results show that the semi-conical piers are eventuated remarkable reduction (up to 25%) in downward flow velocity in the upstream side of the piers, and much more reduction (up to 46%) in bed shear stresses in comparison with the cylindrical pier. Moreover, the model results showed some decrease in vortex shedding frequency for the semiconical piers compared to the cylindrical pier.

Hybrid Large Eddy Simulation/Reynolds-Averaged Navier–Stokes Analysis of a Premixed Ethylene-Fueled Dual-Mode Scramjet Combustor

AIAA Journal ◽  
2021 ◽  
pp. 1-17
Author(s):  
Tanner B. Nielsen ◽  
Jack R. Edwards ◽  
Harsha K. Chelliah ◽  
Damien Lieber ◽  
Clayton Geipel ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Navier Stokes ◽  
Dual Mode ◽  
Eddy Simulation ◽  
Scramjet Combustor ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Simulation of Vortex Instability in a Pipe Trifurcation

2003 ◽  
Author(s):  
Albert Ruprecht ◽  
Ralf Neubauer ◽  
Thomas Helmrich
Keyword(s):  
Large Eddy Simulation ◽  
Turbulence Model ◽  
Model Test ◽  
Reasonable Agreement ◽  
Navier Stokes ◽  
Extended Version ◽  
Vortex Instability ◽  
Flow Phenomenon ◽  
Eddy Simulation ◽  
Large Eddy

The vortex instability in a spherical pipe trifurcation is investigated by applying a Very Large Eddy Simulation (VLES). For this approach an new adaptive turbulence model based on an extended version of the k-ε model is used. Applying a classical Reynolds-averaged Navier-Stokes-Simulation with the standard k-ε model is not able to forecast the vortex instability. However the prescribed VLES method is capable to predict this flow phenomenon. The obtained results show a reasonable agreement with measurements in a model test.

Large Eddy Simulation of Cross Flow in Pipe Junction

2018 ◽  
Author(s):  
Jiajun Chen ◽  
Yue Sun ◽  
Hang Zhang ◽  
Dakui Feng ◽  
Zhiguo Zhang
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Exciting Force ◽  
Navier Stokes ◽  
Pipe Network ◽  
Eddy Simulation ◽  
Large Eddy

Mixing in pipe junctions can play an important role in exciting force and distribution of flow in pipe network. This paper investigated the cross pipe junction and proposed an improved plan, Y-shaped pipe junction. The numerical study of a three-dimensional pipe junction was performed for calculation and improved understanding of flow feature in pipe. The filtered Navier–Stokes equations were used to perform the large-eddy simulation of the unsteady incompressible flow in pipe. From the analysis of these results, it clearly appears that the vortex strength and velocity non-uniformity of centerline, can be reduced by Y-shaped junction. The Y-shaped junction not only has better flow characteristic, but also reduces head loss and exciting force. The results of the three-dimensional improvement analysis of junction can be used in the design of pipe network for industry.

scholarly journals Implicit large eddy simulation of shock-driven material mixing

2013 ◽  
Vol 371 (2003) ◽  
pp. 20120217 ◽  
Author(s):  
F. F. Grinstein ◽  
A. A. Gowardhan ◽  
J. R. Ristorcelli
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Mixing ◽  
Initial Conditions ◽  
Spatial Scales ◽  
Late Time ◽  
Eddy Simulation ◽  
Geometrical Complexity ◽  
Planar Shock ◽  
Large Eddy ◽  
Implicit Large Eddy Simulation

Under-resolved computer simulations are typically unavoidable in practical turbulent flow applications exhibiting extreme geometrical complexity and a broad range of length and time scales. An important unsettled issue is whether filtered-out and subgrid spatial scales can significantly alter the evolution of resolved larger scales of motion and practical flow integral measures. Predictability issues in implicit large eddy simulation of under-resolved mixing of material scalars driven by under-resolved velocity fields and initial conditions are discussed in the context of shock-driven turbulent mixing. The particular focus is on effects of resolved spectral content and interfacial morphology of initial conditions on transitional and late-time turbulent mixing in the fundamental planar shock-tube configuration.

Large Eddy Simulation of the Flow Around a Diffuser-Equipped Bluff Body in Ground Effect

2011 ◽  
Author(s):  
Lara Schembri Puglisevich ◽  
Gary Page
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Vortex Formation ◽  
Ground Effect ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Flow Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features

Unsteady Large Eddy Simulation (LES) is carried out for the flow around a bluff body equipped with an underbody rear diffuser in close proximity to the ground, representing an automotive diffuser. The goal is to demonstrate the ability of LES to model underbody vortical flow features at experimental Reynolds numbers (1.01 × 106 based on model height and incoming velocity). The scope of the time-dependent simulations is not to improve on Reynolds-Averaged Navier Stokes (RANS), but to give further insight into vortex formation and progression, allowing better understanding of the flow, hence allowing more control. Vortical flow structures in the diffuser region, along the sides and top surface of the bluff body are successfully modelled. Differences between instantaneous and time-averaged flow structures are presented and explained. Comparisons to pressure measurements from wind tunnel experiments on an identical bluff body model shows a good level of agreement.

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