| Summary: | 碩士 === 國立成功大學 === 機械工程學系 === 104 === In this study, the interaction of a stream of water drops aligned in a vertical direction was examined experimentally using a free-falling drop apparatus, which provided different gaseous flows, namely, no flow (quiescent air, vg = 0 m/s), convective air flow (vg = 0.3 m/s and 0.5 m/s) and hot flow (vg = 2.5 m/s). The initial drop diameter (di) was kept at 900 μm. In addition, there were three different numbers of drops to consider in the study, two drops, three drops and a drop stream, and three initial dimensionless drop spacings, Si ≈ 2.5, 5 and 10, were selected in the experiment. In the second part, two different initial drop diameters were considered, 900 μm and 1100 μm.
The results showed that the merged collision of drops is controlled by the wake effect, which depends on the initial drop spacing (Si), Reynolds number (Re), initial drop diameter (di), and number of drops. The initial drop spacing has a dominant influence in comparison with the others. In the downward moving process of drops with given values of Si and di, the initial merged collision of the first two drops was observed, after which they merged into a large drop; thereafter, this large drop was caught by the rear drop to achieve the second merged collision. The first merged collision occurred either along the same axis or in an off-center situation, but the second merged collision occurred only in the off-center situation. The results showed that the merged collision position shifted to the downstream region with increases in vg, Si, di or the number of drops under fixed di and vg.
|
|---|
