The effect of the cavity behind Rectangle Bluff Body in turbulent single-phase flow was studied using Particle Image velocimetry (PIV). The results for the time-averaged velocity showed a recirculation flow behind the bluff body. The horizontal location behind the bluff body where the time-averaged vertical and horizontal velocity components were zero was found at approximately 1.2H and the end of the re- circulation region was shifted upstream by effect of the cavity.

Flow control of flow field is essential to design efficient elements relating to fluid machineries. In this study, the flow characteristics of rectangular prism with throughflow at different aspect ratio was investigated to flow control. A particle image velocimetry technique was employed to obtain detailed measurements at throughflow-velocity-based Reynolds numbers. As a results, the throughflow disturbs the development of vertical velocity component and decreased the vortex size.

난류 경계층 유동과 물체주위의 상관유동 및 그 물체 주위에서의 부압 생성과 관련, 그 유동특성에 대한 이해를 높이기 위하여 두꺼운 난류 경계층 내에 놓인 큐브물체 주위의 박리유동에 대해 연구를 수행하였다. 2차원의 PIV와 열선유속계를 이용하여 풍동 내에서 두꺼운 경계층을 생성시키는 실험이 수행되었다. 실험은 큐브의 높이 h에서 측정된 유속 U에 근거한 레이놀즈 수 18,600에서부터 349,000 의 범위에서 수행되었으며, 이 레이놀즈 수의 범위는 평균유동이 레이놀즈 수와 관계없이 충분히 크다고 판단된다. 본 연구에서 큐브의 선단주위와 상부에서의 유동장 측정결과들을 제시할 것이다. 연구결론으로 레이놀즈 효과는 평균표면압력이라든지 표면근처의 평균유속과 같은 평균유동특성에 별 영향을 미치지 않았지만, 섭동장은 큰 영향을 나타내고 있었다.

This work was performed to investigate the distribution of the fuel droplet size around the bluff-body and the combustion characteristics. The geometry of the bluff-body influenced the spray shape and the combustion characteristics. Diameters of the bluff-body in this experiment are 6, 8, and 10mm and the impingement angles( θ) are 30°, 60°, and 90°. The measurement points were at the distances of 20 and 30mm axially from the nozzle. The SMD and Rosin-Rammler distribution was acquired by image processing technique(PMAS), and the mean temperatures were measured by thermocouple. The results obtained are as follows; In the condition of θ=60°, the values of SMD are not greatly varied compared to the other conditions. As the impingement angle of bluff-body was increased, the high temperature region was wider along radial direction. When the air-fuel ratio was increased, the CO concentration was decreased.