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

δe/δb

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.