VMS- and OES-based hybrid simulations of bluff body flows

International audienceFlows past bluff bodies show turbulent near wall behavior in various conditions. For example, for a high Reynolds incident flow, the boundary layer at front side of a circular cylinder may show a transition to a turbulent boundary layer. After separation, the back of the cylinder is in contact with the turbulent wake. Analogously, the turbulent wake of a first obstacle can hit the front of a second one

Grid-Adapted FUN3D Computations for the Second High Lift Prediction Workshop

Contributions of the unstructured Reynolds-averaged Navier-Stokes code FUN3D to the 2nd AIAA CFD High Lift Prediction Workshop are described, and detailed comparisons are made with experimental data. Using workshop-supplied grids, results for the clean wing configuration are compared with results from the structured code CFL3D Using the same turbulence model, both codes compare reasonably well in terms of total forces and moments, and the maximum lift is similarly over-predicted for both codes compared to experiment. By including more representative geometry features such as slat and flap brackets and slat pressure tube bundles, FUN3D captures the general effects of the Reynolds number variation, but under-predicts maximum lift on workshop-supplied grids in comparison with the experimental data, due to excessive separation. However, when output-based, off-body grid adaptation in FUN3D is employed, results improve considerably. In particular, when the geometry includes both brackets and the pressure tube bundles, grid adaptation results in a more accurate prediction of lift near stall in comparison with the wind-tunnel data. Furthermore, a rotation-corrected turbulence model shows improved pressure predictions on the outboard span when using adapted grids

Dynamic Effect of an Active Deformable Flat Plate on Its Turbulent Flow

Updated contributions reflecting new findings presented at the ERCOFTAC Symposium on Unsteady Separation in Fluid-Structure Interaction, 17-21 June 2013, St John Resort, Mykonos, GreeceThis paper addresses the topic of the influence of the profile of a plate on a turbulent flow. The study is based on numerical results obtained by URANS and hybrid (DDES) turbulence modeling and compared with experimental results. The flat plate has an aspect ratio of 20 (length over thickness) and the edges are not smoothed. The plate includes Shape Memory Alloys (SAM), which allows it to arch under the effect of an electric voltage. The deformation by the material corresponds to a beam deformation and is implemented in the numerical simulation according to this definition. The Reynolds number is Re=200,000 , which led to a turbulent flow with a Von Karman vortex shedding and Kelvin Helmotz instabilities in the shear layer. The simulations are performed with several turbulence models: k- ϵ-OES, k-ω-BSL-OES, k-ω-DDES-BSL-OES, k-ω-DDES-SST-Menter. These models are used in a first step to determine the three-dimensional flow around the plate plane inclined by 10∘ . The behavior of the flow are found similar between experiment and numerical simulations. The purpose of the curve shape by deformation is then compared to a linear form by rotation of the plate. The curved shape provides the same lift coefficient with less required deformation and thus with a lower drag coefficient and also a lower frequency. The dynamic deformation is slow compared to the freestream velocity, it weakly affects the coefficients and frequencies compared to linear shape