Abstract
The damage effects of ship structures under the contact jet loads of bubble are studied by using an electric spark bubble as well as high-speed photography. A series of model experiments of ship structures under contact explosion was carried out in a water tank. On the one hand, we monitored the displacement and period of the oscillation of a hull plate of a ship model with a large bending rigidity. On the other hand, we observed the overall motion of a box-beam model with a small bending rigidity. The results show that when the distance parameter is less than 0.6, the bubble jet will impact on the surface of the structure directly, which is defined as “contact bubble jet” herein. The contact bubble jet causes significant local loads on the ship and induces the “sagging moment” effect. This mainly results from the relatively negative bending moment caused by the bubble attached to the hull. With the increase of detonation distance, this negative bending moment decreases. As a result, the oscillation amplitude of the ship structure decreases sharply and the oscillation period reduces gradually.
Highlights
Underwater explosion (UNDEX) has been an effective way to attack surface vessels and underwater submarines
It is generally thought that UNDEX generates two types of loads mainly (Cole, 1948 [1]): the primary shock wave and the following bubble
A large number of studies have been done on the damage effects of shock waves in UNDEX, but a relatively lower number of studies have been done on those of bubbles
Summary
Underwater explosion (UNDEX) has been an effective way to attack surface vessels and underwater submarines. Following the shock wave, the bubble expands and collapses many times while it migrates to the free surface, causing a whipping response of the structure (ISSC, 2015 [8]) Another feature of bubble behavior near rigid surfaces is the attraction to the wall during its contraction, which is known as Bjerknes force (Bjerknes, 1966 [9]). It seems from the previous studies that few researchers studied the impact of bubble jet loads very close to the structure in experiments, or contact impact on the structure, especially on the ship hull This phenomenon happens in the contact UNDEX, exerts high pressure on the ship, and causes severe damage. It is very important to study the damage effects of the contact jet
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