Numerical aspects and implementation of a two-layer zonal wall model for LES of compressible turbulent flows on unstructured meshes

Park, George Ilhwan; Moin, Parviz

doi:10.1016/j.jcp.2015.11.010

Cited by 50 publications

(32 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The downsides of these models are the associated computational costs, as compared to simpler approaches, and also the difficulty of implementing them in solvers suited for unstructured meshes and complex domain geometries. Specifically, the latter implementational aspect has been recently addressed in [37]. Most importantly, there is no consensus regarding whether PDE-based models are necessarily more accurate than less complicated approaches, [22].…”

Section: Introductionmentioning

confidence: 99%

A library for wall-modelled large-eddy simulation based on OpenFOAM technology

Mukha

Rezaeiravesh

Liefvendahl

2019

Computer Physics Communications

View full text Add to dashboard Cite

This work presents a feature-rich open-source library for wall-modelled large-eddy simulation (WMLES), which is a turbulence modelling approach that reduces the computational cost of traditional (wall-resolved) LES by introducing special treatment of the inner region of turbulent boundary layers (TBLs). The library is based on OpenFOAM and enhances the general-purpose LES solvers provided by this software with state-ofthe-art wall modelling capability. In particular, the included wall models belong to the class of wall-stress models that account for the under-resolved turbulent structures by predicting and enforcing the correct local value of the wall shear stress. A review of this approach is given, followed by a detailed description of the library, discussing its functionality and extensible design. The included wall-stress models are presented, based on both algebraic and ordinary differential equations. To demonstrate the capabilities of the library, it was used for WMLES of turbulent channel flow and the flow over a backward-facing step (BFS). For each flow, a systematic simulation campaign was performed, in order to find a combination of numerical schemes, grid resolution and wall model type that would yield a good predictive accuracy for both the mean velocity field in the outer layer of the TBLs and the mean wall shear stress. The best result, ≈ 1% error in the above quantities, was achieved for channel flow using a mildly dissipative second-order accurate scheme for the convective fluxes applied on an isotropic grid with 27 000 cells per δ 3 -cube, where δ is the channel half-height. In the case of flow over a BFS, this combination led to the best agreement with experimental data. An algebraic model based on Spalding's law of the wall was found to perform well for both flows. On the other hand, the tested more complicated models, which incorporate the pressure gradient in the wall shear stress prediction, led to less accurate results. PROGRAM SUMMARYProgram Title: libWallModelledLES Licensing provisions:GPLv3 Programming language: C++ Nature of problem: Large-eddy simulation (LES) is a scale-resolving turbulence modelling approach providing a high level of predictive accuracy. However, LES of high Reynolds number wall-bounded flows is prohibitively computationally expensive due to the need for resolving the inner region of turbulent boundary layers (TBLs) [1]. This inhibits the application of LES to many industrially relevant flows [2] and prompts for the development of novel modelling techniques that would modify the LES approach in a way that allows it to retain its accuracy (at least away from walls) yet significantly lowers its computational cost. Solution method: Wall-modelled LES (WMLES) is an approach that is based on complementing LES with special near-wall modelling that allows to leave the inner layer of TBLs unresolved by the computational grid. Many types * Principal Corresponding Author

show abstract

Section: Introductionmentioning

confidence: 99%

A library for wall-modelled large-eddy simulation based on OpenFOAM technology

Mukha

Rezaeiravesh

Liefvendahl

2019

Computer Physics Communications

View full text Add to dashboard Cite

show abstract

“…Turbulence is generated at the inflow of the domain by a synthetic technique discussed in Section V. Further details about the numerics can be found in Park & Moin. 28 …”

Section: Numerical Detailsmentioning

confidence: 99%

Wall--modeled Large Eddy Simulation of Flow Over a Wall--mounted Hump

Iyer

Malik

2016

46th AIAA Fluid Dynamics Conference

View full text Add to dashboard Cite

Large eddy simulation (LES) with an equilibrium wall model is used to study the flow past a wall-mounted hump at conditions matching the experiments of Greenblatt et al. based on the hump chord (Rec = u∞c/ν∞) is 936,000 and the freestream Mach number (M∞) is 0.1. The Reynolds number of the flow approaching the hump is about 7,000 based on the momentum thickness. This configuration has proved to be a challenging test case with most Reynolds-Averaged Navier-Stokes (RANS) models overpredicting the separation bubble length. While the present wall-modeled LES simulations capture the bubble length within 3.4% of the experiment and mean statistics in the separation bubble reasonably well, they do not accurately predict the skin friction distribution in the separated region. The effect of grid resolution and exchange location for information from LES to the wall model is studied by qualitative and quantitative comparisons to experiment. The fine grid simulation with the exchange location placed away from the wall gives the best agreement overall with experiment.

show abstract

“…(Diurno 2001). Second, most wall-modelling strategies including DES fall into the hybrid RANS/LES methodology in complex geometries, which solves the simplified or full RANS equations in the inner layer and provides wall shear stress boundary conditions for the outer LES region (Cabot & Moin 1999;Piomelli & Balaras 2002;Kawai & Asada 2013;Park & Moin 2016). This hybrid method is not only sensitive to the choice of the RANS model and its associated model coefficients, but also leads to the so-called 'scale disparity' problem 176 W. Gao, W. Zhang, W. Cheng and R. Samtaney on the nominal interfaces between the RANS and LES regions (Germano 2004;Piomelli 2008).…”

Section: Introductionmentioning

confidence: 99%

Wall-modelled large-eddy simulation of turbulent flow past airfoils

et al. 2019

View full text Add to dashboard Cite

We present large-eddy simulation (LES) of flow past different airfoils with$Re_{c}$, based on the free-stream velocity and airfoil chord length, ranging from$10^{4}$to$2.1\times 10^{6}$. To avoid the challenging resolution requirements of the near-wall region, we develop a virtual wall model in generalized curvilinear coordinates and incorporate the non-equilibrium effects via proper treatment of the momentum equations. It is demonstrated that the wall model dynamically captures the instantaneous skin-friction vector field on arbitrary curved surfaces at the resolved scale. By combining the present wall model with the stretched-vortex subgrid-scale model, we apply the wall-modelled LES approach to three different airfoil cases, spanning different geometrical parameters, different attack angles and low to high$Re_{c}$. The numerical results are verified with direct numerical simulation (DNS) at low$Re_{c}$, and validated with experiment data at higher$Re_{c}$, including typical aerodynamic properties such as pressure coefficient distributions, velocity components and also more challenging measurements such as skin-friction coefficient and Reynolds stresses. All comparisons show reasonable agreement, providing a measure of validity that enables us to further probe simulation results into aspects of flow physics that are not available from experiments. Two techniques to quantify hitherto unexplored physics of flows past airfoils are employed: one is the construction of the anisotropy invariant map, and the second is skin-friction portraits with emphasis on flow transition and unsteady separation along the airfoil surface. The anisotropy maps for all three$Re_{c}$cases, show clearly that a portion of the flow field is aligned along the axisymmetric expansion line, corresponding to the turbulent boundary layer log-law behaviour and the appearance of turbulent transition. The instantaneous skin-friction portraits reveal a monotonic shrinking of the near wall structure scale. At$Re_{c}=10^{4}$, the interaction between the primary separation bubble and the secondary separation bubble contributes to turbulent transition, similar to the case of flow past a cylinder. At higher$Re_{c}=10^{5}$, the primary separation breaks into several small separation bubbles. At even higher$Re_{c}=2.1\times 10^{6}$, near the turbulent separation, the skin-friction lines show small-scale reversal flows that are similar to those observed in DNS of the flat plate turbulent separation. A notable feature of turbulent separation in flow past an airfoil is the appearance of turbulence structures and small-scale reversal flows in the spanwise direction due to the vortex shedding behaviour.

show abstract

Numerical aspects and implementation of a two-layer zonal wall model for LES of compressible turbulent flows on unstructured meshes

Cited by 50 publications

References 25 publications

A library for wall-modelled large-eddy simulation based on OpenFOAM technology

A library for wall-modelled large-eddy simulation based on OpenFOAM technology

Wall--modeled Large Eddy Simulation of Flow Over a Wall--mounted Hump

Wall-modelled large-eddy simulation of turbulent flow past airfoils

Contact Info

Product

Resources

About