Flow Characteristics of Wall Synthetic Jet Flowing Over a Circular Cylinder

When jet-based flow control, such as stall control and fluidic thrust vectoring, is employed, jet nozzles are commonly installed near a convex-curved surface. Numerous researchers have investigated the most fundamental curved-wall continuous jet. For synthetic jets, although numerous applied studies exist, fundamental investigations on cylindrical walls remain scarce. Synthetic jets have zero net mass flux; the vortex pair generated during the expulsion phase dominates the suction phase and establishes a time-averaged flow downstream. This study clarifies how a cylindrical surface influences the vortex pair and the resulting mean flow. We performed flow visualization using Particle Image Velocimetry and surface-pressure measurements for a synthetic jet issuing tangentially over a cylindrical surface. We examined the effects of stroke length (the distance fluid particle travels at the representative velocity during one oscillation period) and radius of curvature on the flow. The boundary layer on the wall organized into discrete vortices linked to the dimensionless stroke length, and both the time-averaged pressure distribution and separation point on the cylindrical surface depended on it. Moreover, the vortex street and time-averaged-flow characteristics can be parameterized using a nominal dimensionless stroke based on the radius of curvature rather than the slot width typically used as the representative length.