抄録
Transition in plane Poiseuille flow was investigated by means of flow visualization and hot film velocimeters. The intermittency factor attains the 1 at a Reynolds number of about 2 OOO in natural transition at a minimum critical Reynolds number. But the profiles of turbulent spots are still observable. The flow is fully developed and turbulent for Reynolds numbers greater than 3 OOO. Another experiment was made on spots artificially created in laminar flow over the Reynolds number range 2 000<Re<3 000. The spreading half angle increased from 2° to 10° with increasing Reynolds number from 2 000 to 3 000. The propagation velocity of the leading edge also increased from 0.5umax to 0.6umax.
