Flow Characteristics of Freely Rotating Rectangular Cylinders With Different Width to Height Ratios

The present study numerically investigates flow past freely rotating rectangular cylinders with different width to height ratios. The immersed boundary method (IBM) to model the rectangular cylinder based on the finite volume method is used to study a two-dimensional (2-D) laminar fluid flow for different Reynolds numbers of 50, 100, and 150 in the range of 0.2 ≤ W/H ≤ 1.0, where W/H is the width to height ratio. There are three different regimes of motion. The first one is the periodic oscillation regime. The second one is rotation with reversal of direction regime. The last one is the rotation with one direction regime. All the cases are periodic oscillation regime except the cases of Re = 100 and 150 with W/H = 1.0. For Re = 100 and 150 with W/H = 1.0, the regimes are the rotation with reversal of direction regime and the rotation with one direction regime, respectively. The Strouhal number decreases with increasing the width to height ratio for Re = 50, 100 and 150. However, for Re = 100 and 150, the Strouhal number disappears at a width to height ratio of 1.0. The present study reports the detailed information of flow structure on the cylinder surface at different width to height ratio.