2007 Fiscal Year Final Research Report Summary
Study on Analysis of Non-stationary Ship Motion Data
| Project/Area Number |
17560706
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Naval and maritime engineering
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| Research Institution | Tokyo University of Marine Science and Technology |
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Principal Investigator |
ISEKI Toshio Tokyo University of Marine Science and Technology, Faculty of Marine Technology, Professor (70212959)
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| Project Period (FY) |
2005 – 2007
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| Keywords | TVAR modeling / Instantaneous spectral analysis / Parametric rolling / Instantaneous bispectral analysis / Tri-spectral analysis / non-linear ship motions / Variation of non-linear restoring moment |
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| Research Abstract |
The non-linear ship responses, such as parametric rolling, have become the key issues in the research field of ship stability. After an accident of a post-Panamax container ship happened in 1998, the experimental and theoretical studies in the time domain are carried out vigorously and revision of the Intact Stability Code of the International Maritime Organization (IMO) is now under way.
The main objective of this research is development of new techniques for analyzing the spectral structure of non-stationary ship responses. The research work was continued for three years from the theoretical and experimental viewpoints. The results are summarized below:
1. Theoretical results: The non-linear pitching motion in following seas and its fluctuating skewness were investigated. Since the geometrical phase-relationship between waves and ship's hull can be considered as the main cause of the fluctuating skewness, the phenomenon was simulated by using simplified equations of motion for a single-degree-of-freedom and the instantaneous bispectral analysis, which is based on Time-varying coefficient autoregressive (TVAR) modeling and an extension of the instantaneous power spectral analysis, was proposed. The effectiveness of the proposed method was shown for analyzing the transition of skewness of non-linear ship responses. Finally, the characteristics of the parametric rolling were confirmed by applying the tri-spectral analysis.
2. Experimental results: On board measurements were carried out using the training ship Shioji-maru and the radar wave observation system at Nojima cape was used to obtain reliable wave data in corporation with Japan Coast Guard. Furthermore, a 1/40 scale self propulsive model ship was made up by loading the hand-made control unit, motion sensor and RS232C wireless communication unit to measure the large amplitude ship motion data.
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Research Products
(20 results)
