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Some Warship Slamming Investigations
DEFENCE RESEARCH ESTABLISHMENT ATLANTIC DARTMOUTH (NOVA SCOTIA)
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Excessive slamming is the most common cause of speed reduction for frigates and destroyers in heavy head seas. DREAs early interest in frigatedestroyer slamming was limited to the development of computer programs for ship seakeeping performance prediction. Published bottom slamming algorithms were adopted and refined to provide a slamming prediction capability for DREA software. In follow-on work described herein, both two-dimensional numerical simulations and three-dimensional model tests were performed by contractors to obtain better physical insight and expand the empirical data base. The two-dimensional numerical simulation results required considerable smoothing to reduce numerical noise, but still yielded form factors in satisfactory agreement with two-dimensional theoretical and experimental results The simulations also 1. gave unique insight into the girthwise development of slamming pressures. The three-dimensional model tests indicated that pivoted drop tests in waves may be substituted for conventional seakeeping tests, but the general applicability of the results was limited by difficulties with measurement of relative impact velocity. Notwithstanding the velocity measurement difficulties, the three-dimensional tests provided important information on longitudinal and girthwise pressure pulse velocities. Further experimental work will be required to develop a usable experimental data base.
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