Combined Passive/Active Flow Control of Drag and Lift Forces on a Cylinder in Crossflow Using a Synthetic Jet Actuator and Porous Coatings

Abstract

This paper combines a synthetic jet actuator (SJA) and a leeward porous coating to alter the aerodynamic forces on a cylinder in crossflow at Re = 4.2 × 104. While SJAs and porous coatings are known to be effective flow control methods in isolation, their combined effect has not been studied. A 2D numerical model was created of a cylinder with a SJA at 90° and 100° leeward porous coating. The model was validated using accompanying water tunnel tests. The combined model was tested for dimensionless frequencies 0.15 <f+< 4 and compared to reference models. For f+< 1, using only the SJA increases the cylinder drag coefficient (Cd). Combining a porous coating with the SJA in that regime lowers the Cd values by 15–21%, and causes an overall reduction in Cd compared to the smooth cylinder baseline case. However, using only the porous coating causes a superior 35% reduction in Cd. For f+> 1, the combined SJA and porous coating configuration did not differ from the SJA only configuration, achieving the largest drag reduction of 45% at f+ = 4. The flow control mechanisms of the SJA and porous coating do not combine constructively in this current setup. However, the porous coating is beneficial for f+< 1, causing an overall drag reduction even when the active SJA tends to increase drag.

Internal shear layer and vortex shedding development of a structured porous coated cylinder using tomographic particle image velocimetry

“…Surface pressure fluctuations of an SPCC were recorded by Maryami et al (2023) who used remote pressure sensing to observe the fluctuating lift and drag components at the outer diameter and explained the coherence between fluctuating pressures at various circumferential stations. An identical SPCC design has been applied to the leeward side of a cylinder for passive and active flow control (Yu et al 2021;Xu et al 2022b) and similar square-shaped pore designs have been used for drag reduction purposes (Farrell, Gibbons & Persoons 2022). More complex SPCCs have been implemented (Bathla & Kennedy 2020) and structured porous airfoil leading edges (Bowen et al 2022) and trailing edges (Zhang & Chong 2020;Scholz et al 2022) are used successfully for passive flow and noise control.…”