Studies On Mechanisms Of The Interaction Between High-power Laser And Matter In Water

The laser-induced plasma shock waves propagation, laser-generated bubble dynamics and cavitation destruction mechanisms during the high-power laser and matter interaction in liquids are systemically investigated, as well as experimental measurement and numerical simulation of characteristic parameters.According to constraint conditions of the point-explosion spherical shock wave transmission in free space, it is first proposed the propagation characteristic of laser-induced plasma shock wave in air. The relation between the intense shock motion and thermodynamic variables as well as acoustical properties of mediums is established. These shock propagation formulas overcome defects in the famous Taylor model in the near and far field. Furthermore, Taylor equations are proved to be the approximation expression of the shock transmission formulas in the medium distance. Besides, the temporal and spatial variation of some important parameters on the shock front, including temperature, pressure, density and particle velocity are obtained.Based on non-ccntrosymmetry structure of laser-induced shock wave in liquids,the rotation ellipsoid plasma shock model in liquids is first proposed. The transfer laws of the shock front from an ellipsoidal to spherical distribution, as well as the shock parameters variation are revealed. It is proved the point-explosion spherical shock wave is a special case of the ellipsoidal wave in theory and by experimentBy the self-developed optical detection technique based on fiber-coupling beam deflection principle, the laser-induced plasma shock wave, laser-generated bubble and bubble-collapse-induced shock wave are investigated by experiment during the high-power laser interacts with a underwater target The temporal-spatial variation of plasma shock, the detachment of the plasma shock from bubble expansion wall, the bubble oscillation property and the bubble-collapse-induced shock wave formation are analyzed in detail. Further, based on the bubble dynamics, associated with the experimental results, the variation of the gas-vapor amount in the cavity during the bubble pulsation process is estimated and the effects of the bubble energy and gas-vapor content on the bubble oscillation are discussed.Effects of the cavitation destruction mechanisms on laser processing are investigated by experiment The relation between the cavitation effect and non-dimension parameter isestablished. The experimental results show that for in the range of 0.67 ~ 0.95, the destructive effect due to the liquid-jet plays a vital role during the cavitation bubble collapse, while, the bubble-induced shock wave in effect outweighs the liquid-jet impact.These research results will provide the theoretical and experimental reference to laser processing underwater, laser medicine and corresponding hydromechanics.