The Water Laser Plasma Vacuolization And Experimental Study Of The Shock Wave Propagation Characteristics

The generation of laser-induced acoustic waves in water and propagation are investigated.the cavitation bubble dynamics,plasma shock wave evolution and frequency analysis are measured experimentally and calculated numerically.By optical shadow method of electronic delay, the growth and collapse of a cavitation which is produced by laser-induced plasma were investigated. With the image of the different delayed time,the bubble evolution was observed,and bubble collapse duration was obtained. compared the calculation of the maximum bubble radius with the size of shadow photo, the results are basically the same. From the date of bubble radius at the delayed time, analysis the causes of the velocity of bubble evolution, in the experiment, the clear images are obtained about the plasma shock wave and bubble expansion wave and collapse wave.Used the HNP-1000 needle hydrophones to detect laser-induced acoustic waves.. Study of the attenuation characteristics of laser-induced plasma shock wave, within the first 20cm, sound pressure amplitude decreases rapidly with increasing distance. With the transmission distance farther away, the sound pressure still decreases, but at this time decay rate is slowed, the shock wave has been attenuated to sound waves. Finally, the frequency characteristics of a shock wave propagation have been studied, the peak intensity of the frequency is decreased with the shock wave propagation, the attenuation is large within the 2.5cm, then as the distance increases, the peak intensity continued to decline, but slowed.at 3cm,the frequency curve is smooth, spread to 12cm and 16cm,the curve oscillation more severe, the authors believed it may be the water medium absorbed the wave of some frequency.These results help to provide theoretical and experimental basis about the application of cavitation underwater,and the target detection and location.