Transition to Turbulence in Pipe Flow: Experimental Conditions for Minimum Critical Reynolds Number

摘要

This article describes the experimental conditions for the laminar-turbulent transition problem in pipe flow, particularly associated with the minimum critical Reynolds number. Our earlier study theoretically verified, with a new interpretation of the Reynolds number, that (i) under natural small- or medium-amplitude disturbance conditions, the transition only takes place in the entrance region. Moreover, another earlier study experimentally showed that (ii) the critical Reynolds number is determined by the entrance shape, and that the critical Reynolds number only takes its minimum value of about 2050 when using a sharp-edged entrance pipe under natural disturbance conditions. Here, conditions (i) and (ii) and a few transition features associated with the determination of critical Reynolds numbers are considered on the basis of previous experimental results and the transition model.