Visualization and heat transfer study of a synthetic jet impinging on a circular cylinder

Abstract

The present study deals with a slot fluid jet impinging onto an electrically heated circular cylinder in water. The continuous and synthetic jets were tested. The slot nozzle width was 0.36 mm, the cylinder diameter was 1.2 mm, and the cylinder-to-nozzle spacing, related to the slot width, was 5–21. The Reynolds numbers based on the nozzle width ranged 35– 170. The Laser-Induced Fluorescence (LIF) visualization revealed a dominant flow separation occurring on the windward cylinder side for both continuous and synthetic jets. The flow around the leeward cylinder side is completely absent. It is attributed to the effects of the mini scale and low Reynolds numbers. An increase of the Reynolds numbers changes flow pattern from a steady jet-flow separation to a vortex shedding wake-flow regime. Heat transfer experiments were validated in a natural convection regime. An enhancement of average Nusselt numbers by 4.2–6.2 times by means of the synthetic jets was quantified by comparison with the natural convection regime. A correlation for the average Nusselt number was proposed for both continuous and synthetic jets.