Model for Enhancing Turbulent Production in Laminar Separation Bubbles

Laminar separation bubbles are one of the main critical aspects of flows at low Reynolds numbers in the range of 104 –105 . The flow separates in the laminar regime, the turbulence developing inside the recirculation region enhances the momentum transport, and the flow can reattach. Models based on the Reynolds-averaged Navier–Stokes equations suffer two of main issues: the determination of the transition onset and the level of the pressure recovery downstream of the reattachment of the flow. A model addressing both issues is presented in this paper. It is based on the γ transition model for the transition detection. The production of the turbulent kinetic energy κ has been properly enhanced thanks to a correlation found between the necessary boosting of κ and the intermittency function behavior within the bubble. The low-Mach-number and Reynolds-number flows around the Selig–Donovan 7003, Eppler 387, and NACA 0015 airfoils are analyzed. The results are compared to experimental data and large-eddy simulations available in the literature. The model can be applied to the analysis of an arbitrary airfoil without need of preliminary calculation of the transition point within the bubble.