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

Wei Gao, Wei Zhang, Wan Cheng, Ravi Samtaney

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


We present large-eddy simulation (LES) of flow past different airfoils with, based on the free-stream velocity and airfoil chord length, ranging from to. 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. The numerical results are verified with direct numerical simulation (DNS) at low, and validated with experiment data at higher, 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 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, 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, the primary separation breaks into several small separation bubbles. At even higher, 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.
Original languageEnglish (US)
Pages (from-to)174-210
Number of pages37
JournalJournal of Fluid Mechanics
StatePublished - Jun 24 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): URF/1/1394-01
Acknowledgements: The Cray XC40 Shaheen II at KAUST was used for all simulations reported. This research was partially supported under KAUST OCRF URF/1/1394-01 and under baseline research funds of R.S.


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