A Study on Ultra-Highspeed Micro-Flow

为了弄清超高速微流场的流动特性和动力学特性，对超高速微流场的空化特性进行了研究。然后，系统地观察了喷管内部和喷管出口附近的流态以及窄水道中的空化射流，并对空化流进行了数值模拟。所得结果总结如下：1。我们测试了超纯水，其电阻率大于18 MOMEGA/cm。并且，我们明确了水的相对空气含量比自来水和静水高得多，这是空化发生和发展的一个重要因素。为了避免污染超纯水，我们制作了一种特殊的设备，使用特殊的过滤膜对超纯水中的空气进行脱气，得到了相对空气含量小于0.2.2的特殊超纯水。为了系统地阐明超高速流的流态，对超高速水射流在空气和水中进行了观察和冲蚀试验。以水中射流为例，表明射流周期性地脱落空化气泡云。侵蚀强度也与空化气泡云密切相关。本文系统地研究了浸没式高速水射流周围空化引起的冲蚀特性，浸没式高速水射流在清洗和喷丸过程中具有重要的应用价值。在浸没水射流的情况下，气泡破裂时的空化冲量压力可以有效地用于清洗和喷丸。并给出了几种喷嘴的合适注射条件。为了弄清窄水道中超高速流态，利用最大帧率为40500帧/秒的高速摄像机和数字图像处理技术，对窄水道中的空化射流进行了仔细观察。窄水道内的空化泡云与上述空化云一样具有周期性脱落，伴有严重的侵蚀空化。少

In order to make clear the flow characteristics and the dynamics in the ultra-highspeed micro-flow, we examined the cavitation characteristics of the ultra-highspeed flow. Then, we systematically observed the flow pattern in the nozzle and near the nozzle-outlet as well as the cavitating jet in a narrow watercourse, and also tried to simulate the cavitating flow numerically. The obtained results are summarized as follows :1. We tested the ultra-pure water, whose resistance rate is more than 18 MOMEGA/cm. And, we made clear that the relative air content rates of the water, which is an important factor on the cavitation inception and develops, are considerably higher than that of tap-and still water. Then we made a special facility to degas the air within the ultra-pure water by using a special filtering membrane in order to avoid polluting the ultra-pure water, and we got the special ultra-pure water, whose relative air content rates are less than 0.2.2. In order to make clear the flow … More pattern of ultra highspeed flow systematically, we carried out the observation and the erosion test on ultra highspeed water jets in the air and in the water. In the case of the jets in the water, it is shown that the jets are periodically shedding the cavitation bubble clouds. And also the erosion intensity is closely related to the cavitation bubble clouds.3. The above-mentioned the erosion characteristics induced by the cavitation around the submerged highspeed water jets are systematically examined, the submerged water jets are very useful for cleaning and peening. Since the cavitation-impulse-pressures at the bubble collapsing can be effectively used on the cleaning and the peening, in the case of the submerged water jets. And also the suitable injection condition is shown for several nozzles.4. In order to clarify the ultra highspeed flow pattern in a narrow watercourse, the cavitating jet in a narrow watercourse is carefully observed by means of a highspeed video camera, whose maximum framing rate is 40,500 frames per second and a digital image processing technique. The cavitation bubble clouds in the narrow watercourse are periodically shedding as same as the above-mentioned cavitation clouds associated with severely erosive cavitation. Less