A numerical and experimental study of a transitional separation bubble

A combined numerical and experimental study of a two-dimensional transition al separation bubble due to an adverse pressure gradient is reported. The e xperiments have been performed in the MTL wind tunnel with a contoured wall imposing an adverse pressure gradient on the flow over a flat plate. The s eparated shear-layer is highly unstable and transition to turbulence occurs in the flow. The experimental separation bubble flow is modelled numerical ly using two-dimensional direct numerical simulations (DNS). Prescribing fr ee stream boundary conditions in the wall normal velocity the experimental bubble is reproduced. The development of artificially forced two-dimensiona l instability waves is investigated and good agreement is found between exp eriments, simulations and linear stability theory (LST). The performance of several engineering transition prediction methods applied on the present s eparation bubble is presented and compared. Methods based on simplification s of the e(n)-method yield predictions in accordance with experiments and D NS. (C) 2001 Editions scientifiques et medicales Elsevier SAS.