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박통일(Tongil Park),김대겸(Daegyoum Kim) 한국가시화정보학회 2016 한국가시화정보학회지 Vol.14 No.3
A sweeping jet actuator (SJA) is an instrument generating pulsing jets with no moving elements. Because of its simple design and high durability to shock and vibration, SJA has recently drawn increasing attention for the application to flow control such as aerodynamic control of a wing and thrust vectoring of a jet engine. However, experimental and numerical studies on SJA have been limited to internal flow structure of SJA. In this study, we investigated the flow structure and its variation in the outlet of SJA. We carried out the experiment to understand the flow structures using PIV (Particle Image Velocimetry). The flow structure varies with a degree of the outlet and volume flow rate. There is leaking process during half jetting cycle. The process of the main jet can occur because the jet moving time increased from one side to the other side.
곡면에 충돌하는 스위핑 제트의 유동 구조와 열전달 특성
김동주(Dong Ju Kim),정세영(Seyoung Jung),박통일(Tongil Park),김대겸(Daegyoum Kim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
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. Constant heat flux uniformly on the surface through the measurement procedure. Flow visualization using particle image velocimetry and modal decomposition analysis of the jet flow field were conducted in the separated setting. The result suggests 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.