Research On The The Pulsed Discharge Processes Of Underwater Source And Its Related Bubble Dynamics

Underwater plasma acoustic source, based on the technology of underwater pulsed discharge, is an ideal sound source for CUIS(Counterring Underwater Intruder System). However, the theory on underwater pulsed discharge is juvenility, the analysis concerning prebreakdown and breakdown of underwater pulsed discharge and the vibrational process of the bubble are still being disputed. The whole process of underwater pulsed discharge is still lack of systemic analysis. Therefore, the whole process of underwater pulsed discharge is primarily analyzed. The main work of this paper is summaried as follows:1. A testing system is established for underwater pulsed discharge, and the pressure and current signals are measured. A typical pressure wave measured by the testing system is analyzed. The discharge process is discovered to be divided into two phases, namely prebreakdown discharge phase and violent discharge phase. The peak of the pressure at the point of 15cm away from the centre of discharge is in the order of MPa. At the same time, the peak of the current is in the order of tens of thousand amperes.2. The time of prebreakdown discharge phase measured in experiment, is theoretically analyzed. Prebreakdown discharge phase is a stochastic process; the randomness of this phase will be decreases with the increase of discharge voltage; and the average time will be reduced with the raise of discharge voltage.3. The possibility of existing of cylindrical bubbles is analyzed from the point of view of energy. Three expressions of cylindrical bubbles are deduced from three different hypothesises, and are compared with each other.4. In order to quantitatively analysis the gasous polytropic index, an expression for this gasous polytropic index changing with the velocity of bubble wall is put forward and used in the numerical calculation of acoustic cavitation, which is compared with the experimental data.5. The whole process of underwater pulsed discharge is divided into four phases, namely streamer breakdown phase, prebreakdown phase, violent discharge phase and bubble pulsation phase, where the violent discharge phase is analyzed in details, the pressure, number density, temperature, radius, conductivity, resistance of the plasma channel, and the shock wave in the liquid are analyzed. Compared with the experimental data, very good agreement is found.