Transition Modelling for General Purpose CFD Codes

Abstract

This chapter addresses modeling concepts based on the Reynolds averaged Navier–Stokes (RANS) equations for laminar-turbulent transition prediction in general-purpose computational fluid dynamics (CFD) codes. Available models are reviewed, with emphasis on their compatibility with modem CFD methods. Requirements for engineering transition models suitable for industrial CFD codes are specified. The main criterion is that nonlocal operations should be avoided. The γ-Reθ transition model was built on these requirements. The model solves two transport equations and can be applied to any arbitrary geometry. Current limitations of the model are that cross-flow instability is not included in the correlations and that the transition correlations are formulated non-Galilean invariant. Both limitations are currently investigated and can in principle be removed. An overview of test cases computed with the new model is given. The purpose of the overview is to highlight that the model can handle a wide variety of geometries and physically diverse problems. It is suggested that the central concept of combining transition correlations with locally formulated transport equations has a strong potential for including first-order transitional effects into today's industrial CFD simulations.