Study on Cavitation Erosion Mechanism and its Prediction

这项为期两年的计划的主要目标是研究空化侵蚀的机理及其预测。空化气泡崩塌产生的冲击力是一个关键特性，无论是对空化侵蚀机理的研究还是对空化侵蚀的预测，测量都是可取的。两名成员分别于1995年和1996年在格勒诺布尔的IMG呆了两个月，进行关于传感器可靠性和准确性的合作研究实验。在CAVERMOD涡流空化腐蚀试验装置上，对两种类型的压电式传感器(压电陶瓷和PVDF)和一种新型的氧化镁晶体传感器进行了测试。三种传感器的增益吻合得很好，证实了这些传感器可以作为标准。云空化和撞击涡空化的数值分析。通过对测量到的金属表面凹坑形状的分析，估算冲击压力分布。假设Strouhal相似和水锤效应，通过模型的坑计数预测原型的侵蚀强度。根据实测的冲击力分布预测侵蚀强度。提出了一种无需实验即可预测撞击力分布的方案。流体特性，如声阻抗、表面张力、粘度对侵蚀的影响。

The main objective of this two year program is research on mechanism of cavitation erosion and its prediction.Impact force caused by collapsing cavity bubble is a key property and the measurement is desirable mostly both for research of the mechanism and for the prediction. Two members stayd two months in 1995 and 1996 at IMG,Grenoble for cooperative research experiments on the reliability and the accuracy of sensors. Two types of piezo sensors (piezo ceramic and PVDF) and a new sensor of MgO crystal were tested in a vortex cavitation erosion testing facility, named Cavermod. The gain of the three sensors agreed very well among them and it was confirmed that those sensors can be used as standard.The following researches were made by the members of the present program.1. Numerical analysis of cloud cavitation and impinging vortex cavitation.2. Estimation of impact pressure distribution by analysing measured pit shapes on metal surface.3. Prediction of erosion intensity on prototype from pit counting of model assuming Strouhal similarity and water-hammer effect.4. Prediction of erosion intensity from measured impact force distribution.5. Proposal of a scenario for prediction of impact force distribution without experiment.6. Effect of fluid properties such as acoustic impedance, surface tension, viscosity, on erosion.