Application of submerged water jets to the decomposition of organic compounds with the aid of compressibility effects in bubbly water flows.

目前的研究是开发一种可替代的空化水射流装置，与传统的浸没水射流相比，该装置可以在显著低的射流操作压力下分解污染水中的有机化合物。本工作的一个基本思路是利用激波来定位气泡破裂的发生，这有望导致溶解在水中的有机化合物的有效分解。本研究的结果总结如下：1。当通过水喷嘴的气泡流满足产生激波的条件时，溶解于水中的有机化合物的分解速率增加，尽管目前实验所达到的增加速率仍低于最初的预期水平。在较低的流速范围内实现超声速气泡流动有两种补充方法；一种是利用人工产生的微气泡，另一种是在喷嘴上游的流动中引入轴对称旋转运动。对水中气泡生长的数学和数值分析表明，当环境压力高于已知满足初始条件的所谓临界压力时，空化就会发生。本文建立了一套描述液气混合运动的空间平均模型方程，并将其应用于收敛-发散型喷嘴流动的计算中，为实际计算具有空化现象的高速液体流动提供了一种很有前途的方法。

The present research has been made to develop an alternative cavitating water-jet facility which enables to decompose organic compounds in contaminated water at significantly low jet-operating pressures compared to customarily used submerged water jets. A basic idea in the present work is to utilize shock waves for localizing the occurrence of bubble collapse, which is expected to cause the efficient decomposition of organic compounds dissolved in water. The results of this study are summarized as follows.1.The decomposition rate of organic compounds dissolved in water increases when the bubbly flow through the water-jet nozzle meets the condition to generate shock waves, although the rate of increase attained so far in the present experiments remains within an extent lower than the initially expected level.2.Two supplemental means are found to be useful for realizing supersonic bubbly flows in a moderately low range of the flow velocity ; one is the use of artificially generated microbubbles, and the other is the introduction of axisymmetrically rotating motion in the flow upstream the nozzle.3. Mathematical and numerical analyses of the bubble growth in water show that the cavitation inception can occur at an ambient pressure higher than the so-called critical pressure below which the inception condition is known to be satisfied.4. A set of space-averaged model equations describing the motion of liquid-gas mixtures, which was recently developed in our laboratory, is applied to the computation of convergent-divergent nozzle flows, and is found as a promising method for the practical calculation of high-speed liquid flows with cavitation.