Electroacoustic Process Study of Plasma Sparker Under Different Water Depth
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AbstractThe plasma sparker has been applied in oceanic high-resolution seismic exploration for decades. Normally it is towed on the water surface. This is suitable for shallow water, but if the water depth is great, the resolution will decrease dramatically, especially in the horizontal direction. This paper proposes the concept of a deep-towed plasma sparker and presents an experimental study of plasma sparker performance in terms of electric parameters, bubble behavior, and acoustic characteristics. The results show that hydrostatic pressure at a source depth ranging from 1 to 2000 m has a negligible influence on the electric parameters but a strong influence on bubble behavior, wherein both the maximum bubble radius and oscillation period are decreased. The collapse pulse vanishes when the source depth reaches 1000 m or deeper, and no bubble oscillation can be distinguished. The source level (evaluated by the expansion pulse) is also decreased as the source depth increases; moreover, the greater the discharge energy, the smaller the source level loss. The discharge energy per electrode should be greater than 20 J for the deep-towed plasma sparker, which can make the source level loss induced by hydrostatic pressure smaller than the transmission loss. The fast Fourier transform (FFT) results show that the dominant energy is around 20 kHz, which is mainly induced by the expansion pulse and its oscillation. According to the simulation results, the fundamental frequency of the acoustic waveform increases with source depth in accord with a log linear trend, and also reaches tens of kilohertz in deep water. So, before the development of deep-towed plasma sparker, a new technical solution will need to be developed to solve this problem. © 1976-2012 IEEE.
CitationHuang Y, Zhang L, Zhang X, Li S, Liu Z, et al. (2015) Electroacoustic Process Study of Plasma Sparker Under Different Water Depth. IEEE Journal of Oceanic Engineering 40: 947–956. Available: http://dx.doi.org/10.1109/JOE.2014.2382451.
SponsorsManuscript received March 03, 2014; revised May 30, 2014 and November 24, 2014; accepted December 11, 2014. Date of publication January 05, 2015; date of current version October 09, 2015. This work was supported by Fundamental Research Funds for the Central Universities in China, Chinese National High Technology Development Program under Grants 2013AA065001 and 2013AA065005; by the National Natural Science Foundation of China under Grant 41476080; and by the National Science Foundation (NSF) of Zhejiang Province under Grant LQ14D060004.