Turbulent Wake of Rectangular Cylinder Near Plane Wall and Free Surface

Abstract

This paper reports an experimental study of turbulent wake of a two-dimensional rectangular cylinder in a 2500-mm long, 186-mm wide, and 197-mm deep recirculating open channel. The water level upstream of the cylinder was maintained at 100 mm while the aspect and blockage ratios, defined, respectively, as the cylinder's length to thickness and the cylinder thickness to water depth, were 9 and 0.12. The cylinder was mounted across the channel at three different vertical locations: relatively close to the plane wall, close to the free surface, and relatively remote from both the plane wall and the free surface. For each of the preceding three locations, a particle image velocimetry technique was used to conduct detailed measurements at various streamwise-transverse planes around and downstream of the cylinder. For each test condition, the freestream velocity of the approach flow was kept constant at 0.356 m/s. The Reynolds number based on the cylinder thickness was 4270 and the Froude number was 0.36. From these measurements, the streamlines, isocontours of mean vorticity, as well as the mean velocities and turbulent quantities were obtained to document the effects of the plane wall and the free surface on the flow characteristics.