The whipping response of a submerged free-free cylinder due to underwater explosions

Underwater explosions (UNDEX) generated by torpedos and mines present one of the most significant threats to the survivability of naval vessels. A non-contact UNDEX event produces two distinct pressure loading phenomena: an initial short duration, high frequency shock wave followed by a relatively low frequency pulsating bubble containing the gaseous products of detonation. The pulsating bubble may excite global, beam-like, structural response modes of the vessel, known as UNDEX induced whipping. Depending on the size and position of the explosive charge relative to the vessel, the maximum strain levels during whipping may exceed those during the initial shock phase. Due to the large costs of full-scale explosive trials, development of validated numerical modelling procedures for UNDEX whipping and shock response are required to assess the survivability of naval vessels. An experiment has been conducted to investigate the UNDEX whipping response of a fully submerged cylindrical pipe structure considering the effects of different charge sizes, stand-off distances and longitudinal positions along the hull. It was found that the longitudinal stand-off location has a significant influence on the whipping response and that the peak whipping response may not always occur at the stand-off point.