The influence of a divergent slot on the near-wake region of a circular cylinder

Abstract

Controlling flow around a circular cylinder is essential for reducing drag, alleviating lift fluctuations, and enhancing aerodynamic efficiency in various engineering applications. In the present work, the effect of localized passive air-jet injection at different azimuthal angles on the near-wake region of circular cylinder was numerically investigated at subcritical Reynolds numbers Re = 3900 and 20,000 using ANSYS-FLUENT commercial software. The slot angle was varied from 70° to 130° with an increment of 10°. To insure the reliability of the current numerical model, the simulation results were validated with available experimental and numerical literature. The results revealed that the slot can significantly affect the flow structure in the near-wake region and pressure distribution around the cylinder at slot angles 100° ≤ θs ≤ 130°. It was found that the optimum slot angle was 130° at which a good pressure recovery on the rear surface of the cylinder was achieved. Moreover, turbulent kinetic energy in the very near-wake region showed a substantial decrease of 40 % compared to the BL case at lower tested Reynolds number, as well as an 11 % reduction in the extent of the recirculation region. The drag analysis showed that the drag can be reduced by 26 % when the slot inclined at 130°. It can be concluded that the position of the slot induced jet plays a vital role on the flow structure, pressure distribution, and drag coefficient. Additional experimental studies are required to further explore the impact of the slot on the wake region. Specifically, investigating the combined effect of 70° and 130° slot angles could provide deeper insights, potentially leading to a more significant influence on the wake region

Keywords

• Passive flow control
• Slot-induced jet
• Divergent slot
• Wake control
• Drag coefficient