Turbulent flow measurement by the ADV in the vicinity of a rectangular cross-section cylinder placed at a channel sidewall

Abstract

This paper presents the findings of an experimental study on the three-dimensional turbulent flow field in the vicinity of a rectangular cross-section cylinder placed at the sidewall of a rectangular open channel. Uniform sand of median diameter 0.52 mm was glued over the channel bottom to make it rough. Detailed measurements of the time-averaged velocity components, turbulent intensity components, turbulent kinetic energy and Reynolds stresses were taken by the acoustic doppler velocimeter (ADV) at different vertical sections around the cylinder. In the upstream, presentation of flow fields through vectors at vertical and horizontal sections show a primary vortex associated with the downflow near the cylinder. On the other hand, in the downstream, the flow field shows a three-dimensional separated flow with vortex shedding. Using the Reynolds stresses and velocity gradients, the bed shear stresses are determined. In front of the cylinder, the velocity and the bed shear stress are found to be approximately 1.6 and 3.3 times of their magnitudes at free flow upstream zone, respectively. The data presented in this paper would be useful to the investigators for the development and verification of mathematical models of flow field in the vicinity of vertical-wall abutments.