Seakeeping Characteristics of the XR-5, A High Length-Beam Ratio Manned Surface Effect Testcraft: III. Results of Random Wave Experiments Investigation of Linear Superposition for Ship Motions and Trim and Draft in Random Waves

Seakeeping Characteristics of the XR-5, A High Length-Beam Ratio Manned Surface Effect Testcraft: III. Results of Random Wave Experiments Investigation of Linear Superposition for Ship Motions and Trim and Draft in Random Waves

Author: Joseph J. Ricci

Publisher:

Published: 1976

Total Pages: 63

ISBN-13:

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Motion responses derived from model experimental results in regular and irregular head waves for the XR-5 high length-beam ratio surface effect ship are presented. Frequency response functions for pitch, heave, relative bow motion, heave acceleration and bow acceleration were computed from the random wave experiments and are presented herein. Comparisons are made with responses derived from regular wave experiments. The results indicate that the rigid body motions are reasonably linear for the Froude numbers and sea conditions investigated. Nonlinear effects that increase with the severity of the sea state are evident in the accelerations. In addition, the motion of the stern seal with respect to the relative motion at the stern is presented. These responses are generally linear although some nonlinear effects appear with increasing Froude number. Probability distributions for the double amplitude of wave height, heave and pitch are presented. Comparisons are made with Rayleigh probability distributions based on the variances of the sample data and on the minimum Chi Square estimators computed from the distributions. (Author).


Journal of Hydronautics

Journal of Hydronautics

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Publisher:

Published: 1977

Total Pages: 504

ISBN-13:

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A publication of the American Institute of Aeronautics and Astronautics devoted to marine science and technology.


Seakeeping Characteristics of the XR-5, a High Length-Beam Ratio Manned Surface Effect Testcraft: II. Results of Linearity Investigation, Effects of Changes from Reference Operating Condition and Trim and Draft in Regular Waves

Seakeeping Characteristics of the XR-5, a High Length-Beam Ratio Manned Surface Effect Testcraft: II. Results of Linearity Investigation, Effects of Changes from Reference Operating Condition and Trim and Draft in Regular Waves

Author: Allen H. Magnuson

Publisher:

Published: 1975

Total Pages: 53

ISBN-13:

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Motion responses in regular head waves for the XR-5 high length-beam ratio surface effect ship are presented. Frequency response functions based on an equivalent amplitude derived from the total energy are presented for pitch, heave, relative bow motion, heave acceleration and bow acceleration. These are compared with responses computed from the first harmonic component of each signal. The results show that the pitch, heave, relative bow motion and bow acceleration exhibit linear behavior for the Froude numbers investigated. Some nonlinear behavior is evident in the heave acceleration at frequencies near the natural frequency in pitch. The effect of varying lift fans and duct valve settings on the response is determined. The pitch magnification is shown to increase when the duct valves are opened beyond the reference settings. Trim angles and drafts for the reference operating condition are presented as a function of encounter frequency for three speeds. The results indicate a moderate variation in trim and draft with frequency.


Seakeeping Characteristics of the Xr-5, a High Length-beam Ratio Manned Surface Effect Testcraft

Seakeeping Characteristics of the Xr-5, a High Length-beam Ratio Manned Surface Effect Testcraft

Author: Allen H. Magnuson

Publisher:

Published: 1975

Total Pages: 89

ISBN-13:

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Motion response data for regular waves in head seas is presented for a model of a high length/beam ratio surface effect ship (SES). Data is presented in normalized form for pitch, heave, relative bow velocity, relative bow motion, stern seal motion, bow acceleration and heave acceleration. The pitch motion data exhibits a resonant or underdamped behavior governed by a constant natural frequency throughout the speed range investigated. The wave pumping effect was observed in the supercritical frequency range, and was particularly evident in the normalized acceleration data. The relative bow motion exhibits a pronounced peak at a frequency slightly above the pitching natural frequency.


Wave Excitation and Vertical Plane Oscillation Experiments on a High Length-to-Beam Ratio Surface Effect Ship

Wave Excitation and Vertical Plane Oscillation Experiments on a High Length-to-Beam Ratio Surface Effect Ship

Author: James A. Fein

Publisher:

Published: 1976

Total Pages: 77

ISBN-13:

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Captive model experiments were conducted on a high length-to-beam ratio surface effect ship testcraft design to determine vertical plane characteristics and to evaluate captive model experimental techniques. Model results for forced heave oscillation and pitch oscillations, and regular-wave exciting forces and moments and transient-waves exciting forces and moments are reported. The effects of sidewalls and cushion pressure variation on the oscillation results are identified. The correlation between the regular waves and transient waves techniques for determining the excitation is shown. (Author).