Modular Turbulence Modelling Applied to an Engine Intake

The one equation Spalart Allamaras (SA) turbulence model in an extended modular form is employed for the prediction of cross wind flow around the lip of a 90 degree sector of an intake with and without surface roughness. The flow features around the lip are complex. There exists a region of high streamline curvature. For this the Richardson number would suggest complete degeneration to laminar flow. Also there are regions of high favourable pressure gradient (FPG) sufficient to laminarize a turbulent boundary layer (BL). This is all terminated by a shock and followed by a laminar separation. Under these severe conditions, the SA model is insensitive to capturing the effects of laminarization and the reenergization of eddy viscosity which promotes the momentum transfer and correct reattachment prior to the fan face. Through distinct modules, the SA model has been modified to account for the effect of laminarization and separation induced transition. The SA modules have been implemented in Rolls-Royce HYDRA Computational Fluid Dynamic (CFD) solver. They have been validated over a number of experimental test cases involving laminarization and also surface roughness. The validated modules are finally applied in unsteady RANS mode to flow around an engine intake and comparisons made with measurements. Encouraging agreement is found and hence advances made towards a more reliable intake design framework.