摘要

In this paper, we report a combined experimental and LES study of transient flow in a rectangular channel accelerating from an initial turbulent flow following the opening of the control valve. We show that this transient flow undergoes a process of laminar-turbulent transition even though the initial flow is turbulent. This is consistent with the findings from the numerical studies of idealised flow transients (He & Seddighi 2013, 2015 and Seddighi et al 2014). The transient flow is characterised by a time developing laminar-like boundary layer, which later becomes unstable and breaks up into turbulence. This process is similar to the bypass transition of spatially developing boundary layer.