Numerical investigations of dynamic stall characteristics with laminar-to-turbulence transition

The influence of laminar-to-turbulence transition of the laminar separation bubble (LSB) on the dynamic stall process of a pitching foil was investigated using transition SST k-ω turbulence model. As the LSB moves to the leading edge, the strong strain rate produces a pronounced laminar-to-turbulence transition, resulting in a turbulent mixing, faster turbulent reattachment, and shrinkage of LSB. This transition leads to the enhancement of the friction coefficient after the reattachment point and delays the suction collapse and evolution of secondary vortex. A baseline SST k-ω model was also applied. Without the transition mechanism, the suction collapse occurs too early, and the downstroke relaminarization is absent. The oscillation of the downstroke lift curve is severer using the SST model than that using the transition SST model. This study extends the detailed validations of transition model and helps improve the understanding of the influence of the transition on the dynamic stall process.