Zonal Detached Eddy Simulation of a spatially developing flat plate turbulent boundary layer

The present work presents a Zonal Detached Eddy Simulation (ZDES) to simulate a spatially developing turbulent boundary layer over a smooth flat plate at Reθ = 2900. Results are compared with the experimental data of De Graaff and Eaton [1]. A synthetic reconstruction method for the pseudo-viscosity field ν˜ is proposed in the frame of a synthetic eddy method. First, it is shown that ZDES amounts to LES with a plausible one-equation subgrid scale model and wall modeling. More precisely, both the mean and second-order field are well predicted compared with the experiment and a reference LES with the mixed-scale-model. The separate effect of the streamwise (respectively spanwise) resolution on skin friction and turbulence is then evaluated. A measure of the global error which is based on the error on the friction and on the turbulent shear stresses has been defined. It is observed that without fixing the height of the RANS-LES interface, the error does not vary monotonicaly with the resolution. Conversely, fixing the interface height to 50 or 100 wall unit brings both an intuitive reduction of the error with the resolution and a global reduction of the error level with respect to the aforementioned case. Furthermore, it is outlined in this study of spatially developing boundary layer that the potential computational effort reduction brought by RANS-LES approaches depends not only on the grid resolution but also on the establishment distance of the solution.