突变流道内空化准周期特性研究

采用环路动态实验测量和数值模拟方法对突变流道内的空化过程进行了研究，通过不同位置空泡气相体积分数、压力波动和频谱规律分析考察了不同空化状态下的准周期演化特性，发现不同空化状态下频谱规律不尽相同。由云状空化过程中的气相体积分数和压力波动分析可知，流场内存在两类波动频率，分别以空泡团的低频脱落和微小空泡的高频再生、汇聚形式存在；同时发现不同空化状态下低频、高频变化规律的差异与空泡的形态和汇聚演化过程紧密相关。这种现象阐释了空化准周期演化过程的本质是微小空泡周期性生长后汇聚成团或直接脱落所导致的。

Quasi-Periodic Characteristics of Cavitation in Sudden Change Channel

Cavitation process in a sudden change channel was studied with both loop dynamic experimental measurement and numerical simulation. Quasi-periodic evolution characteristics under different cavitation states were investigated through volume fraction analysis, pressure fluctuation and frequency spectrum of cavitation at different positions. It is found that the frequency spectra under different cavitation states are different. According to gas volume fraction analysis and pressure fluctuation in the cloud cavitation process, there are two kinds of fluctuation frequencies in the flow field. The above two frequencies are caused by low-frequency shedding of cavitation clusters, and high-frequency regeneration and convergence of micro cavitation, respectively. At the same time, it is found that the difference of low-frequency and high-frequency variation under different cavitation states is closely related with the shape and convergence evolution process of cavitation. This phenomenon explains that the essence of quasi-periodic evolution process of cavitation is caused by aggregation or direct shedding of micro-cavitation after periodic growth.