Control of flow dynamics around a cylinder using sweeping jets

Flow control of cylinders aimed at drag reduction or vibration suppression has been widely studied. Sweeping jet is a novel flow control method that has been applied to airfoil and other bluff bodies. This paper numerically investigates the flow control effects of sweeping jets on a cylinder at a Reynolds number of 5 × 104 using large Eddy simulation. Various parameters such as jet angle, jet momentum coefficient, and the arrangement configuration of fluidic oscillators are examined for their influence on flow control effectiveness. The results demonstrate that sweeping jets significantly reduce the cylinder's drag, mitigate lift fluctuations, suppress vortex shedding, and extend the length of the recirculation region. The optimal jet angle is 70°, and at a jet momentum coefficient of 3.4 × 10−3, the drag reduction reaches a maximum of 47%, while the standard deviation of the lift decreases by 92.2%. As the jet momentum coefficient increases, the drag reduction factor (defined as the ratio of the reduced drag to baseline drag) rises. However, when the coefficient exceeds 3.4 × 10-3, the drag reduction rate decreases significantly, accompanied by changes in the wake flow pattern. Besides, the arrangement density of the fluidic oscillators also plays a crucial role in flow control effectiveness. Furthermore, the interaction between the sweeping jets and incoming flow is examined. The sweeping jets upstream of the separation point exchange momentum with the boundary layer, enhancing stability and suppressing separation. The closer the jets are to the separation point, the more effective the suppression.