Search

The empirical time-varying resistance model of the plasma channel $R_{\mathrm {pl}}(t) = \beta l^{2}/W_{\mathrm {in}}(t)$ in underwater discharge has been widely used, but the internal energy of the plasma channel $W_{\mathrm {in}}(t)$ is difficult to obtain and the discharge coefficient $\beta $ varies widely under different experimental conditions. This article introduces an improved empirical plasma channel resistance model $R_{\mathrm {pl}}(t) = \beta l^{2}/E_{\mathrm {pl}}(t)$ as well as a method for determining the discharge coefficient $\beta $. The effectiveness and the feasibility of the method are verified by comparing the simulation results and test results. The improved plasma channel resistance model and the method to determine the discharge coefficient can help guide the application of electrohydraulic shockwaves. [ABSTRACT FROM AUTHOR]

This paper reports on analysis of two different types successive underwater shock waves generated by a device incorporating a compact shock-wave generator with a magnetic pulsed compression circuit. To generate shock waves, underwater pulsed electric discharges in high-impedance saline water were used. The saline water made possible underwater shock waves propagation in tissue with low reflection between the solution and tissue boundary, owing to their similar acoustic impedances. A cylindrical electrode holder and a semiellipsoidal shock-wave focusing reflector/generator were used in this paper. The diameter of the compact shock-wave reflector was 20 mm. Two kinds of successive underwater shock waves, one generated by electric discharge plasma expansion and the other by bubble collapse, were observed. The shock waves were studied by time-resolve high-speed visualization and direct pressure measurement using a fiber optic probe hydrophone pressure transducer. The former method elucidated propagation of underwater shock waves and behavior and collapse of the bubble near the electrodes, while the later measured two kinds of underwater shock waves pressures at different voltage amplitudes using the cylindrical electrode holder and the shock focusing generator. This paper clearly shows the importance of the secondary shock waves, their control, and damping, for effective and safe medical application of shock waves. [ABSTRACT FROM PUBLISHER]

Pulsed power, used to produce underwater discharges, has been the subject of numerous studies to elucidate its mechanisms and applications. This paper reports on observation by a high-speed camera of the production and progress of streamer discharges created using a magnetic pulse compression pulsed power generator with maximum output energy of 40 Joules per shot in the medium of both tap and distilled water. Bubble production along streamers, bubble collapse, generation of shock waves, and extinction of bubbles was also observed by a high-speed camera. [ABSTRACT FROM PUBLISHER]

We are developing the rice powder manufacturing system using an underwater shock wave. The purpose of this study is to research a mechanism of the shock wave generation and energy efficiency by underwater discharge in order to increase energy of the underwater shock wave. We observed the shock wave generation using the visualization device with a high speed camera, and measured voltage current characteristics at the same time. As a result, it was clarified that countless underwater shock waves were generated at the time of water plasma expansion by discharge. But, the shock wave was not confirmed at the time of after a second peak of the damping oscillation. It was clarified that one part of charging energy was used to generation of the shock wave. Therefore, it was clarified that to release energy by the critical oscillation is desirable for efficient generation of the shock wave. [ABSTRACT FROM AUTHOR]

Food processing utilizing underwater shock wave softens the food by breaking cells, and prevents loss of nutrients since there is little influence of heat. Moreover, it is also possible to extract a nutrient easily and reduce processing time. A device to generate a high intensity shock wave is required in order to process various kinds of food. The purposes of this research are to investigate the best condition to generate high intensity shock waves and to understand the behavior of converged shock wave.The capacitor electric discharge circuit was used as an underwater shock wave generating device. The waveform of discharge voltage and current were measured in order to search for the best condition of underwater discharge. It was confirmed that the larger charge voltage of capacitors become, the larger optimum electrodes interval become. Propagation and convergence of underwater shock wave was observed by numerical analysis. [ABSTRACT FROM AUTHOR]