Flow past rotating cylinders using deterministic vortex method

This study examines the performance of an in-house code based on a deterministic vortex method on circular and square cylinders rotating with constant velocity. Subjecting a bluff body to rotary about its axis effectively reduces drag forces, suppresses the fluctuating forces, and increases the lift forces (known as the Magnus effect). Rotating cylinders are well known for their use in rotor ships, rotor aircrafts, and wind turbines. This study aims to establish the accuracy of the in-house code for the rotating circle cylinders based on the results from the literature and examine the behavior of the rotating square cylinders (a less-studied case). A square section, as a many-sided shape, can be considered when the behavior of more complex geometries is of interest, such as trajectories of the sediments, or replacing circular sections when autorotation is of importance. Both cylinders are exposed to a uniform flow of Re = 200 and an imposed rotation rate range of 0 <= alpha <= 5.5 for the circular, and 0 <= alpha <= 5 for the square cylinder. The present numerical tool is able to predict the vortex shedding suppression as a result of forced rotation. For both cases, a systematic increase in the time-averaged lift coefficient (approximate to 25.5 for the circular and approximate to 26 for the square case when alpha = 5) and a general descending trend in the time-averaged drag coefficient (approximate to 0.03 for the circular and approximate to 0 for the square case when alpha = 5) are detected. The second mode of vortex shedding for the circular cylinder is captured within a narrow range of rotation rates. A noticeable feature of the flow over rotating square cylinders is the emergence of near-field wakes in the near-body region, which develop independently from the wake behind the body. To the best of the authors' knowledge, this is the first comprehensive study of a rotating body carried out using a deterministic vortex method-based numerical tool.

Automated summary

This study examines the performance of an in-house code utilizing a deterministic vortex method on the rotation of circular and square cylinders. The results show that rotational motion reduces drag forces, suppresses fluctuating forces, and increases lift forces. The code accurately predicts vortex shedding suppression and identifies the emergence of near-field wakes in the flow over rotating square cylinders.