United States Navy – Naval Special Warfare Combatant Craft Division, Norfolk Detachment

Michael Riley, The Columbia Group
Kelly Haupt, NSWCCD Det Norfolk
Donald Jacobson, NSWCCD Det Norfolk
Timothy Coats, NSWCCD Det Norfolk

This brief presents an analysis of the acceleration response motions of a high-speed planing craft in waves. These motions are of interest because a broader awareness and a better understanding of cause and effect physical relationships in high speed wave impacts could be applied in craft design or comparative craft system evaluations to address multiple factors associated with seaworthiness, including hull design loads, stability, component ruggedness, and crew or passenger comfort and safety.

The paper builds on lessons learned from historical stochastic analysis methods that transition the randomness of ocean waves and full scale trials data to useful peak acceleration values. Parameters such as the average of the one-tenth and one-hundredth highest peak acceleration values are discussed, and the root- mean-square acceleration value is explained and applied in a new procedure for estimating the average acceleration amplitude for each wave slam event. The limitations of statistical approaches related to user subjectivity are summarized, and a new deterministic analysis methodology is presented that characterizes the rigid-body responses of the craft in terms of acceleration, velocity, displacement, and rotation motions during each wave impact event. Time-history comparison plots of various individual wave impact events are presented, new wave impact parameters and types of impacts are defined, and the results of regression analyses are presented. The results demonstrate that peak rigid-body acceleration values are repeatable and scalable. The limitations of these results are summarized and further research is suggested for achieving a broader level of knowledge for future applications.

Current hull design methodologies and seakeeping criteria are based on the solid foundation of understanding related to the randomness of ocean waves. It is envisioned that these methods coupled with the new analysis approach presented in this paper could help researchers, designers, engineers, builders, and operators increase their awareness and understanding of the dynamics of high-speed wave impacts in planing hulls. The increased awareness and understanding could have broad applications for improved standard processes, including structural design, correlation with computational modeling and simulation methodologies, correlation of full-scale and scale-model test data, comparative evaluations of different craft, and development of criteria for improved ruggedness and personnel comfort and safety.