Abstract
This paper compares the threshold energy and time for transition to turbulence for three scenarios in the temporal case for Poiseuille flow (PPF) and the Blasius boundary layer (BL). The three scenarios are: TS wave - nonlinear 2D state - secondary instability of 2D state; vortices - streaks - secondary instability of streaks; and oblique waves - vortices - streaks - secondary instability of streaks. For both flows the lowest energy transition is achieved by the third scenario. For PPF, the threshold energy transition for the first is about two orders greater than for the second and the third. In the BL, the second scenario is the most competitive. The Reynolds number increases in the downstream direction. (AIAA)