Author(s): Hiroji Nakagawa; Iehisa Nezu
Abstract: Turbulence measurements of the backward-facing step flow, including the reverse flow region, in an open channel were conducted using a two-component Laser Doppler anemometer. The mean velocity distribution and turbulence characteristics were revealed in and around the separated shear layer and recirculation region (separation bubble). Reattachment properties and the dynamic pressure distribution were analyzed varying the Reynolds and Froude numbers. The structure of the shear stress was also analyzed on the basis of the momentum equation. The separated step flow and its recirculation in an open channel are similar to that in boundary layer and duct flows. But, the former is more complicated than the latter, because the pressure is relaxed by the existence of the free surface. Finally, the exchange processes of mean-flow and turbulent energies as well as momentum were examined downstream of the step.