1997 Fiscal Year Final Research Report Summary
Development of Measuring System for Stability of a High-Speed Craft Using an Unmanned Towing Carriage
| Project/Area Number |
08555248
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
船舶工学
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| Research Institution | Osaka Prefecture University |
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Principal Investigator |
IKEDA Yoshiho Osaka Prefecture University, College of Engineering, Professor, 工学部, 教授 (10117989)
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| Co-Investigator(Kenkyū-buntansha) |
OTSUKA Koji Osaka Prefecture University, College of Engineering, Assistant Professor, 工学部, 講師 (90213769)
BABA Nobuhiro Osaka Prefecture University, College of Engineering, Associate Professor, 工学部, 助教授 (10198947)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Instability / Porpoising / Heave / Pitch / Restoring Moment / Planing Craft |
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| Research Abstract |
Measuring systems for ship motions and forces acting on high-speed craft have been developed in the towing tant of Osaka Prefecture University.
Using the system, experimental investigations are performed on the longitudinal dynamic instability, or porpoising, of a planing craft at high advanced speed up to Fn=6.0 in calm water.
Measurements of ship motions are carried out to reveal the characteristics and conditions of porpoising. The results show that the phase difference between heave and pitch is about 90 degrees at any advanced speed.
Captive model tests and forced motion tests are carried out to clarify the influence of the restoring, damping and added mass forces on the dynamic instability, The results show that the coupled heave restoring coefficient from pitch motion decreases with advanced speed and becomes negative at Froude number higher than 0.6, where the dynamic component in the total force are dominant. This suggests that the porpoising is a self-excited oscillation due to the energy exchange between heave and pitch motions.
Porpoising of the model ship are numerically simulated using a non-linear equation with measured non-linear hydrodynamic and hydrostatic coefficients. The simulated heave and pitch amplitudes are in good agreement with the measured results.
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