Abstract
Usually, steady pipe flow is luminar Reynolds number Reis less than 2320, and turbulent when Reis more than 3000. However transition Reynolds number in the acceleration pipe flow is much bigger than that of steady flow, where the transition is only judged by the velocity fluctuation.
Transition to turbulent in acceleration flow has not been proved by flow visualization.
In this paper flow visualization was conducted to prove the transition in accelaration pipe flow.
The relation between acceleration and transition Reynolds number was almost the same as that by Lefebvre.
