Separation-induced transition to turbulence: Second-moment closure modelling

The paper presents some results of application of a low-Re-number second-moment closure (SMC) to modelling the laminar-to-turbulent transition induced by a separation bubble. The same model, tested earlier in a number of low and high-Re-number flows, was found also to reproduce reasonably well several cases of bypass transition, as well as cyclic sequence of laminarization and turbulence revival in oscillating flows at transitional Re numbers, without any artificial transition triggering. The focus of the paper is on separation-induced transition in flow over a flat plate with a circular leading edge, and on a plane surface on which a laminar separation bubble was generated by imposed suction on the wall-opposite boundary. The results show acceptable agreement with available experimental data, large-eddy and direct numerical simulations (LES, DNS). The importance of applying higher-order discretization schemes for reproducing both the bubble and the transition is also discussed.