An Experimental Evaluation of the Local Effects of a Water Microjet on the Cavitation Erosion

1.为了准确区分微射流和冲击波的冲击压力，制作了多个局部压力传感器。每个传感器元件的敏感面积为1 mm × 1 mm，与微射流的主截面几乎相同。通过传感器和空化泡的闪光照片，精确地测量了微射流和冲击波的冲击压力，揭示了空化泡在第一和第二膨胀阶段的冲蚀机理.自制了一种方便的瞬态空化泡运动观测装置。利用CCD线阵图像传感器，在4 MHz的高采样频率下，对气泡运动进行了动态观测。CCD传感器的输出数据经A/D转换器和缓冲存储器系统直接采样后送入微机。该装置对一维数据的采样速度约为37微秒，这对应于约27000帧/秒的高速摄影。将该装置应用于固体边界附近空化泡运动的观测，证实了该装置在观察瞬态空化泡运动和微射流产生方面的有效性。

1. In order to distinguish the impulsive pressures of a microjet and a shock wave precisely, several local pressure sensors are manufactured. Each sensor element has its sensitive area of 1mmX1mm, which is almost the same as the main cross section of the microjet. By the sensor and flash photographs of the cavitation bubble, the impulsive pressures of the microjet and shock wave are precisely evaluated and the erosion mechanism by cavitation bubbles is revealed at the first and second collapsereexpansion stages of the cavitation bubble.2. A handy apparatus is made to observe the transient cavitation bubble motion. The bubble motion is potically observed by a CCD linear image sensor, which is driven by high sampling frequency of 4 MHz. The output data of the CCD sensor are directly sampled by an A/D converter and buffer memory system and transferred to a microcomputer. The sampling speed of the apparatus for one-dimensional data is about 37 microseconds, which corresponds to a high-speed photograph of about 27000 frames/s. The apparatus is applied to observe the cavitation bubble motion near solid boundary and it is confirmed that the apparatus is very useful to observe the transient cavitation bubble motion and the microjet generation.