Analysis of time-frequency characteristics of underwater bottom explosion pressure signals
Due to changes in charge equivalent and the influence of seabed boundaries,the time-frequency characteristics and energy distribution of underwater explosion pressure signals undergo significant changes compared to the explosion of small equivalent charges under free field conditions.In order to obtain the characteristics of underwater bottom explosion pressure signals,measured pressure data was used to analyze using wavelet analysis method,and the characteristics and energy distribution of the signals at different time frequencies were obtained.The analysis results show that the energy proportion of pressure signals in the frequency band below 4 kHz exceeds 95%,the energy proportion in the frequency band below 250 Hz exceeds 75%,and the peak pressure proportion in the frequency band below 250 Hz is 39%.The energy and peak pressure distribution are concentrated in the lower frequency band;The energy proportion during the shock wave period exceeds 64%,and the energy proportion during the after-flow period is about 30%,while the energy proportion during the secondary pressure wave period is about 6%.The explosion energy is mainly concentrated in the shock wave and after flow periods.Therefore,when analyzing the impact response of ship structures and equipment under the condition of underwater explosion,the focus should be on the low-frequency band in the frequency domain,and the impact of the shock wave and after flow period in the time domain.
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