Estimation of Hydrodynamic Derivatives derived from Transient Manoeuvring Tests

Research Project

Project/Area Number	60850084
Research Category	Grant-in-Aid for Developmental Scientific Research
Allocation Type	Single-year Grants
Research Field	船舶抵抗・運動性能・計画
Research Institution	OSAKA UNIVERSITY
Principal Investigator	HAMAMOTO Masami Osaka University, 工学部, 教授 (30107130)
Co-Investigator(Kenkyū-buntansha)	HONDA Keinosuke Kobe University of Mercantile Marine, 商船学部, 教授 (00031427) TAGUCHI Katashi Osaka Prefectural University, 工学部, 教授 (40081385) TATANO Hisayoshi Osaka University, 工学部, 助手 (00029042) HASEGAWA Kazuhiko Osaka University, 工学部, 講師 (60106804)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥9,000,000 (Direct Cost: ¥9,000,000) Fiscal Year 1986: ¥3,000,000 (Direct Cost: ¥3,000,000) Fiscal Year 1985: ¥6,000,000 (Direct Cost: ¥6,000,000)
Keywords	hydrodynamic derivatives / frequency dependency / transient response / impulsive response; causalty / 因果律 / Kramers-Kronigの関係 / 流体力 / 過渡運動 / 操縦性
Research Abstract	Hydrodynamic derivatives including the effect of frequency are estimated by means of transient manoeuvring tests. Planar motion mechanism (PMM) was used for this purpose, but partially changed to allow transient motions. Utilising the Fourier analysis, linear derivatives are obtained in wide frequency range and they coincide with those derived from regular PMM tests. But the reliability of the results deeply depends on the characteristics of input transient motions and on the quality of measured forces. Then, the effect of maximum amplitude and time parameters applied to the transient motions are studied. Each pairs of derivatives (e.g. added mass coefficient and damping coefficient) satisfied the Kramers-Kronig relationship in nature. First, Hilbert transform was applied to the experiment results, and the relationship was confirmed in general. But, there are unnegligible difference, because of the limitation in measured frequency range. Next, supposing the causal system, each transfer function is assumed to a rational function with a finite order of Hurwitz polynominal. If a proper set of coefficients in the transfer function is identified, we need no more to confirm the Kramers-Kronig relationship. Bode's diagram of the transfer function is used for parameter identification, and each experiment result is coincided with the transfer function very well.