Abstract
Effect of initial unsteadiness on transition to turbulence in constant acceleration pipe flow has been investigated experimentally together with the laminar analytical solution. The acceleration pattern in the present study is a combination of a constant deceleration after the steady regime and then a constant acceleration. Three kinds of the zero velocity period between the constant deceleration and acceleration are selected as (Run 1): 0.0 s, (Run 2): 0.5s, (Run3): 5.0s, and the results are compared with that for a constant acceleration from rest (Run 0). The fully developed axisymmetric Navier-Stokes equations are solved for the present target flow to compare the experimental results before the appearance of turbulence. As a result, the zero velocity period could not distinctly affect transition to turbulence except for tz = 0.0 s within the present experimental conditions.
