| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 100 === The research studies the features of round tube jets in a stationary environment and the trajectory analysis of round tube jets in a cross-flow environment. The experiments were carried out in a vertical closed-loop water tunnel. Flow structures were observed by using flow visualization and Particle Image Velocimetry(P.I.V.) techniques respectively.
For round tube jets in a stationary environment, the characteristics of the flow rate and the maximum axial velocity are different for the round tube jets having different Reynolds numbers. Particle Image Velocimetry uses two interrogation cells to analyze captured images. A finer cell has results approaching to the theoretical model. Experimental results show that, the vortex ring formation changes the flow rate and the velocity field of the jet significantly. The velocity profile of the jet is closer to that of Schlichting theory after the vortex ring formation.
For the trajectory analysis results of round tube jets in a cross-flow environment, three different trajectories determined by streamline, velocity and vorticity are notably different when the velocity ratio is less than 3 or larger than 9. This research uses streamline trajectory to analyze a round tube jet in a cross-flow environment. Experimental data are analyzed under two specific conditions of the same velocity ratio and the same cross-flow velocity. Experimental results show that Reynolds number is an important index for jet trajectory for these two conditions. When the Reynolds number of the jet is in the transition region, the trajectory of the jet shows some changes, especially the maximum axial distance which the jet can reach. When the Reynolds number is in the turbulent region, the jet trajectory is similar to those reported in the previous literature.
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