Slamming of High Speed Craft: A Parametric Study of Severe Cases

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Virginia Tech


High-speed planing craft slamming into waves can cause structural damage to the vessel as well as hinder or injure personnel onboard. As a result, it is one of the primary constraints that limit the operating envelope of high-speed surface vessels. The controlled motion experiments presented in this thesis were designed to be an intermediate step between vertical water entry tests of a wedge and a traditional tow tank experiment of a planning hullform in waves. This allowed a deeper study of the hydrodynamic loads that occur during slamming. A planing hull model was subjected to controlled motions in the vertical plane to replicate the types of slamming motions that a vessel may experience in the ocean. The slamming events investigated were chosen based on towing tank experiments previously conducted at the U.S. Naval Academy. Hydrodynamic forces were measured globally and also at particular locations near the bow. The vertical motions were programmed into a pair of linear actuators that were rigidly mounted to the towing carriage. The towing carriage prescribed the horizontal motion. Each actuator was independently controlled and capable of moving at 1.3 m/s and 15 m/s^2. Pressure sensors were used to measure the pressure time history at discrete points on the model. Force sensors mounted beneath the actuators were used to compute the overall slamming load and moments induced by the slam event. A combination of other sensors were used to verify the accuracy of the prescribed motion profile. The results suggested that total impact velocity is correlated with the load growth rate. In addition, the velocity normal to the keel was found to be most impactful on the magnitude of the peak force.



Slamming, Planing Vessels, Controlled Motion