Control of Flow Structures Around a Cylinder in Deep Water Employing a Passive Control Element

Abstract

This study aimed to experimentally investigate the swirling flow characteristic in the periphery of a cylinder located vertically in a deep water channel using a particle image velocity measurement method (PIV). In addition to the PIV method, paint visualization experiments were performed to observe the structures of vortical flow qualitatively. Based on the cylinder diameter, Reynolds numbers were changed incrementally as 2.5 x 10(3), 5 x 10(3), and 7.5 x 10(3), while the length of the control element, L = 180 mm was kept constant. The flexible splitter plate made of a plastic material was easily deformed under the influence of vortical flow. In the horizontal plane, taken from the middleheight of the cylinder, instantaneous flow data was measured first. Along these measurements, the distributions and magnitude of the velocity vectors, < V >, vorticity concentrations, <omega >, patterns of streamlines, <psi >, root mean square of velocity component such as < urms > and < vrms >, correlations of shear stresses, < u'u'>, < v'v'> and < u'v'>, turbulent kinetic energy, TKE, and spectral analysis is conducted to define the frequency, f of vortex formations. The presence of a flexible flow control element located along the central axis line of the cylinder significantly affects the vortex formations. The existence of the flexible flow control element can significantly influence the wake flow region. Furthermore, many of the value of flow characteristics decreased as mentioned with respect to the bare case.