Outer layer turbulence dynamics in a high-Reynolds-number boundary layer up to recovering from mild separation

Abstract

The outer layer dynamics of a high-Reynolds-number boundary layer recovering from non-equilibrium is studied utilising the multi-resolution approach of zonal detached eddy simulation mode 3. The non-equilibrium conditions are obtained from a boundary layer separation over a rounded step enhancing the turbulent production, and recovery happens during redevelopment after reattachment at high Reynolds numbers ( $Re_{\theta,max}\approx 24{,}000$ ). Most of the outer layer turbulence is resolved by the simulation, which reproduces accurately the experimental boundary layer relaxation. The spectral analysis of streamwise velocity fluctuations and turbulent kinetic energy (TKE) production evidences the different turbulent content distribution at separation and within the redevelopment region, at which very large-scale motions are identified with streamwise wavelengths up to $\lambda _x = 9\delta$ , where $\delta$ is the boundary layer thickness. The redevelopment of the boundary layer is analysed in terms of the persistence of a secondary peak in the TKE production and the evolution of the wall-shear stress statistics. The skewness and probability density function of the skin friction show a slower relaxation than the downstream flow fraction. This confirms the long-lasting impact of perturbations of the outer layer in high-Reynolds-number wall-bounded flows. This persistent non-equilibrium state is suggested to be the reason for the reported lack of accuracy of the considered Reynolds-averaged Navier–Stokes models in the relaxation region.

On the Use of Bi-species ZDES for Multi-nozzle Space Launcher Configurations

“…The ZDES approach developed by ONERA [30,31] belongs to the family of multiresolution approaches which covers the full range of modeling from RANS to Wall-Modelled LES (WMLES) [21,32,33] and aims at treating in a simple model all classes of flow problems indicated in Fig. 3.…”

Data-driven wall modeling for turbulent separated flows

“…Hybrid LES/RANS methods are cost effective since they can provide an overall quite satisfactory prediction of turbulence dynamics (e.g. separation point, non-equilibrium turbulence...) with a coarser mesh than would be used in a wall-resolved large-eddy simulation [80,94] An alternative to the resolution of the full RANS equation is to solve the thin-boundary-layer 2 Data preparation and filtering…”