The Royal Canadian Navy: Ready for underwater shocks.

Modern naval vessels must be designed to withstand underwater shock (UNDEX) loads,  meeting survivability standards. The Royal Canadian Navy asked us to thoroughly assess the strength of one of its combatant ships when facing such complex forces. 

To reduce the risk posed by underwater shock events, our client needed to understand the resulting effects caused by ‘whipping’. Calculating the whipping factor was key to this analysis. Our study’s scope covered different charge locations, sizes, and standoffs; the variation in charge details would have an impact on the possible bending stresses experienced by the vessel for a range of foreseeable threats. 

Our applied technology experts brought over 20 years’ experience of underwater shock analyses to this project. The team was supported by our proprietary software, Trident Suite.  

In relation to an underwater blast, whipping is a dynamic response to the charge bubble expansion and collapse resulting from an event. This whipping causes substantial hull girder bending stresses, which may result in large hull and deck deformations, and ultimately, vessel immobility. 

The severity of hull whipping is defined in terms of a whipping factor. At a particular hull cross section, the maximum bending moment identified in the whipping analysis is compared to the allowable bending moment at that section. The ratio of these two values (the former divided by the latter) is the whipping factor. A whipping factor greater than unity implies the hull will not remain elastic and may suffer local damage, induced by whipping.

The whipping analysis enabled our client to ensure that its vessel’s design could withstand extreme global hull girder bending stresses. The naval vessel was prepared for the dynamic response to a shock bubble expansion and collapse.