Comparison of hydrodynamic-impact acceleration and response for systems with single and with multiple elastic modes

Robert W. Miller
Feb 1958

Hydrodynamic-impact tests were made with a multimode elastic model consisting of a rigid prismatic float and a flexible wing, and the results were compared with similar experimental results for a single-mode system and with theoretical solutions. The model had a ratio of sprung mass to hull mass of 0.48 and a first-mode natural frequency of 4.38 cycles per second. The tests were conducted in smooth water at fixed trims of 3 degrees and 9 degrees with flight-path angles of 14 degrees and 6 degrees, respectively, and over a range of velocity. The analysis of the data and comparisons with other experimental and theoretical results indicated that the applied accelerations were in agreement with those obtained by the method of NACA Report 1074 and that the higher modes present in the multimode system had no significant effect on the applied accelerations.

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