Wall-Model for Turbulent Flows Under an Adverse Pressure Gradient - Asymmetric Diffuser

This work presents the comparison of newly developed numerical methods against earlier conventional numerical methods, used in the field of computational fluid dynamics (CFD) to model the boundary layer in turbulent flows with an adverse pressure gradient. The wall model used for comparison in this paper was developed by Manhart (2008). In the estimation of the flow field, the Manhart wall-model considers the contribution of the pressure gradient. The numerical simulations carried out in this paper are based on the Reynolds-averaged Navier Stokes (RANS) equations. The RANS-based numerical simulations were carried out using the k-ω turbulence model where the Shear Stress Transport (SST) was applied. The Manhart wall-model was implemented in the k-ω SST turbulence model. The results from the numerical simulations were validated against detailed experimental measurements. The experimental test case used for validation of the numerical simulation results consists in an asymmetric diffuser, in which a moderate adverse pressure gradient is present. The effects of the adverse pressure gradient were captured using the Laser Doppler Anemometry (LDA) technique, in two different sections of the asymmetric diffuser. The implementation procedure of the Manhart wall model was made using a free, open-source CFD software, Code_Saturne, developed by EDF. The velocity distribution estimated by the Manhart wall model is in good agreement with the experimental data for the viscous wall-layer, while the power computational requirement effort was reduced compared to the standard k-ω SST model.