Transition to Turbulence and Velocity Distribution near the Entrance in Constant-Acceleration Pipe Flow Started from Steady Laminar State

Abstract

Transition to turbulence of a laminar pipe flow accelerated from steady laminar state at a constant acceleration has been experimentally investigated. Air is used as the working fluid and the axial velocity component of the constant-acceleration flow near the entrance of the pipe is measured with a hot-wire anemometer. Transition to turbulence is judged based on the velocity signal and the RMS value of the velocity fluctuation. The results are compared with those obtained for a constant-acceleration pipe flow started from rest. The measured value of the critical Reynolds number in the former case is greater than that in the latter case. The amplification of disturbance does not occur when the initial flow is laminar unlike the case that the liquid is initially at rest.