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EXPERIMENTAL STUDY AND LARGE EDDY SIMULATION OF ACCELERATING FLOW FROM AN INITIAL TURBULENT FLOW

Shuisheng He
School of Engineering The Robert Gordon University Schoolhill, Aberdeen, AB10 1FR, UK; Department of Mechanical Engineering University of Sheffield Sheffield, UK, S1 3JD

Akshat Mathur
Deparmtent of Mechanical Engineering, Univeristy of Sheffield, Sheffield S1 3JD, United Kingdom

Mehdi Seddighi
School of Engineering, University of Aberdeen, Aberdeen AB24 3UE; Department of Mechanical Engineering, University of Sheffield, Mappin Street, Sheffield,S1 3JD, UK; School of Engineering, Technology and Maritime Operations, Liverpool John Moores University, Liverpool, L3 3AF, United Kingdom

Sam Gorji
Department of Mechanical Engineering University of Sheffield Sheffield S1 3JD, United Kingdom

Abstract

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.