Durations of transition and variation of boundary-layer thickness before and after breakdown

Temporal mode direction numerical simulation has been done for the breakdown process of laminar-turbulent transition and the fully developed turbulence in an incompressible boundary layer on a flat plate.Based on the computational results,the common and different characteristics of the durations of transition and the time-averaged boundary-layer thickness induced by different initial disturbances were discussed.Analytical results show that under different basic wave numbers,the durations of transition induced by different initial disturbances are different to one another.On the other hand,under given basic wave numbers,if the initial disturbances are dissymmetrical in span-wise direction,the ratio of the time-averaged boundary-layer thickness after transition to the boundarylayer thickness at the beginning of the breakdown process in the transition,δ_e/δ_b,shows the same growth rate with respect to time,which is independent of the initial disturbances.In contrast,initial symmetric disturbances will induce different growth trends.