Experimental Investigation on Flow Control over a Circular Cylinder Using Antiphase Pulsed Jets

Abstract

To investigate the flow control characteristics of antiphase pulsed jet technology and explore a more efficient method to control unsteady flow with minimal impact on flow turbulence, wind tunnel experiments were conducted. The aim was to address the issue of flow separation control on the surface of a cylindrical model. The model had a diameter of 100 mm, and an experimental setup utilizing an antiphase pulsed jet excitation was developed. The optimisation of unsteady jet control involved adjusting parameters such as jet momentum coefficient, slot position, and excitation frequency. The flow separation control effect on the cylinder surface was compared between in-phase and antiphase pulsed jet using a particle image velocimetry (PIV) technique. The mechanisms of flow control for these two methods were analysed. The results showed that in still air, increasing the jet momentum led to a gradual decrease in the high-velocity region, which also moved away from the wall. Under incoming flow conditions, positioning the slot closer to the separation point resulted in better flow separation control, particularly when the excitation frequency matched the main flow frequency. Both in-phase and antiphase pulsed jet excitations effectively suppressed flow separation. In the near-wall region within the symmetric plane between the two slots, the antiphase excitation reduced the root mean square of velocity fluctuations by approximately 1.9% and increased the average velocity by approximately 15.5% compared to in-phase pulsed jet excitation. In-phase pulsed jets exhibited low-frequency, high-velocity characteristics near the separation point, while antiphase pulsed jets, due to the alternating discharge of the two jets, had a lesser impact on the flow field turbulence.