Influence of explosive charges with different L/D ratios on peak vibration velocity of submarine pipe
In order to reveal the influence of the length-to-diameter ratios of explosives on the peak vibration velocity of submarine pipelines during underwater explosions,finite element(FE)model consisting of water body,seabed soil,TNT explosive and X70 pipe was established and the influence of cylindrical explosive charges with different length-to-diameter(L/D)ratios(1.31＜L/D＜2.83)on the peak vibration velocity of the pipes was numerically analyzed by using FE software ANSYS/LS-DYNA.Moreover,a prediction formula for the peak velocity of submarine pipes subjected to explosion loading was obtained by using the Sadaovsk empirical formula and the least squares polynomial fitting method.The results showed that the vibration velocity of the pipe is periodically attenuated in the range of near-field explosion.In the case of constant-mass charge,the larger the L/D ratio of explosive charge,the greater the peak velocity of the pipe.When the velocity of the front blast surface of the pipe reaches the peak value,the back blasting surface of the pipe will drop to the valley value of the velocity,and vice versa.If one side of the blasting surface and the back blasting surface of the pipe reaches the peak of the vibration velocity,the other side will fall to the trough of the vibration velocity,and the whole process will continue until the charge energy is exhausted.When 3.6＞R＞1.8,compared with the fitting results of Sadaovsk formula,the fitting error of vibration velocity of pipe by quadratic polynomial method is small.In the range of 9＞R＞3.6,both fitting methods are suitable for the vibration velocity fitting of submarine pipe under blast loading.
submarine pipeunderwater explosionpeak vibration velocityfluid-structure interactionlength-to-diameter ratio
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