Heat transfer characteristics and flow structure of sweeping jet impinging on curved surfaces

Impinging jet has been widely applied for convective heat transfer because of its superior performance of removing locally concentrated heat. Impinging sweeping jet has drawn attention recently by the virtue of its capability of generating spatially oscillating flow with a simple non-moving structure and noticeable heat transfer enhancement. In this study, the heat transfer characteristics and flow structures of the sweeping jet impinging on the convex or concave surfaces of different curvatures are experimentally investigated. In order to evaluate heat transfer performance, temperature distribution is measured on the curved surface, and local Nusselt number is computed, while applying constant heat flux uniformly on the surface. Flow visualization using particle image velocimetry and modal decomposition analysis of the jet flow field suggest that unsteady flow structures near a jet centreline and unique vortical structures at the downstream are critical in determining the distribution of the local Nusselt number. In addition, the effects of geometric and dynamic parameters such as surface curvature, nozzle-to-plate distance, and Reynolds number are analyzed.