In recent years, surface ship shock trials have been conducted in many countries for shock qualification of ship integrity, systems and subsystems. A ship trial identifies design and construction deficiencies that have negative impact on ship and crew survivability. Such a trial also validates shock hardening and performance of shipboard equipments. However, live fire ship shock trials and underwater explosion testing are both complex and expensive. As a possible alternative, numerical modeling and simulation may provide viable information to look into the details of dynamic characteristics of ships, including at the component and sub-component levels. Ship shock analyses were conducted using a finite element based coupled catamaran type ship with a fluid model. This model also applies to underwater explosion (UNDEX) simulation for movements with a high speed catamaran type ship. Catamaran type ship shock modeling and simulation has been performed and the simulation results were compared with the empirical data. The high speed craft of catamaran type ship shock analysis approach is presented and the important parameters are discussed.
The first high speed passenger catamaran was built on the Black Sea before World War II. The designer encountered two problems; comfortable accommodation of passengers and reasonable seaworthiness. By that time it was known that a catamaran has better seaworthiness than a mono-hull of greater displacement. In oblique waves, motions of a catamaran are smaller because the hulls do not encounter waves simultaneously. A twin-hull vessel with slender hulls was found to be stable and had good performance features (Dubrovsky and Lyakhovitsky, 2001). Surface ship shock simulation subjected to underwater explosion is generally complicated by free surface effects such as surface reflection waves resulting in bulk cavitation (Shin, 2004). In addition, there are phenomena such as hull cavitation, gas bubble oscillation and migration toward free surface, and cavitation closure pluses (Shin, 2004).