On the Use of Embedded Meshes in the LES of External Flows

In the present study, the possibility of performing cheap and accurate LES computations using unstructured grids on complex geometries has been examined. The test case considered is a turbulent flow around a thin controlled diffusion airfoil at low speed, with angle of attack of 8° to the incoming free-stream flow. The flow velocity is set to satisfy the chord Reynolds number of 1.2 × 105. Two subgrid models are tested; the classical Smagorinsky model and the WALE model. The predictions are found to be in good agreement with the experimental data both in terms of flow dynamics and pressure spectra. The results are found to be independent of the LES physical models tested herein, although this conclusion is issued with the caveat that a careful grid generation procedure using (2:3 and 3:4 type) refinements was required to reduce the jump size across the different grid resolutions.