Experiments on transition in plane Couette flow

TLDR

The experiment used an infinite‑belt Couette flow water channel with counter‑moving transparent walls and reflective flakes to visualize flow, triggering transition with a high‑amplitude pointwise disturbance. The lowest Reynolds number sustaining turbulence was measured at 360 ± 10, and for higher Reynolds numbers a sufficiently large initial disturbance produced a growing turbulent spot whose shape and spreading rate were characterized up to Re = 1000.

Abstract

The first flow visualization experimental results of transition in plane Couette flow are reported. The Couette flow water channel was of an infinite-belt type with counter-moving walls. The belt and channel walls were transparent making it possible to visualize the flow pattern in the streamwise-spanwise plane by utilizing fluid-suspended reflective flakes. Transition was triggered by a high-amplitude pointwise disturbance. The transitional Reynolds number, i.e. the lowest Reynolds number for which turbulence can be sustained, was determined to be 360 ± 10, based on half-channel height and half the velocity difference between the walls. For Reynolds numbers above this value a large enough amplitude of the initial disturbance gave rise to a growing turbulent spot. Its shape and spreading rate was determined for Reynolds numbers up to 1000.