Problem description
The Aerospatiale A-aerofoil flow case is complex case with transition and separation. This flow, a high lift configuration, at an angle of attack of α = 13.3°, a chord Reynolds number of 2 100 000 and a freestream Mach number of 0.15 has been subject of extensive study and is part of the LESFOIL project. It is a challenging case for LES calculations due to the high Reynolds number and the different flow regimes. The strong adverse pressure gradient causes a laminar separation bubble and natural transition, the boundary layer grows and next to the blunt trailing edge there is separation.
Dahlström and Davidson illustrated this in the next sketch.
Software
OpenCruncher, version 6.1
Hardware
NVIDIA RTX A4000 (10x)
Results
Due to the fact that the transition location is not known no wall modeled large eddy simulation (WMLES) or wall function large eddy simulation (WFLES) can be used. This makes this high Reynolds number case expensive to calculate. Here only a WALE subgrid scale model was used with meshes up to 63 million cells.
The surface data, pressure coefficient and skin friction coefficient, shows an agreement with the simulation of Dahlström et al. and the experiment of Gleyzes et al., see the next figure. It was not possible to match the experiment exactly in the trailing edge separation zone and backflow area.
The following figure shows the results of a mesh study with meshes from 5 million cells (mesh 1) to 63 million cells (mesh 3). There is a clear trend towards even finer grids, no grid convergence has been reached yet.
References
S. Dahlström and L. Davidson, “Large Eddy Simulation of the flow around an Aerospatiale A-aerofoil”, European Congress on Computational Methods in Applied Sciences and Engineering – ECCOMAS, 2000
C. Gleyzes and P. Capbern, “Experimental study of two AIRBUS/ONERA airfoils in near stall conditions”, Aerospace Science and Technology, vol. 7, pp. 439–449, 2003