Field Observation of Orbital Motion in Waves
Grant-in-Aid for General Scientific Research (B)
|Allocation Type||Single-year Grants|
|Research Institution||Research Institute for Applied Mechanics|
KOTERAYAMA Wataru Kyushu Univ Research Institute for Applied Mechanics Professor, 応用力学研究所, 教授 (80038562)
光易 亘 九州大学, 応用力学研究所, 教授 (30038533)
NAKAMURA Masahiko Research Institute for Applied Mechanics Research Associate Professor, 応用力学研究科, 助手 (40155859)
KYOZUKA Yusaku Graduate School of Engineering Science, 総合理工学研究所, 教授 (80177948)
堀 勉 九州大学, 応用力学研究所, 助手 (10199523)
|Project Period (FY)
1990 – 1991
Completed(Fiscal Year 1991)
|Budget Amount *help
¥6,900,000 (Direct Cost : ¥6,900,000)
Fiscal Year 1991 : ¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1990 : ¥4,700,000 (Direct Cost : ¥4,700,000)
|Keywords||Field experiments / Wave directional function / Spreading parameter / Wave force coefficients|
In this research project, two major target were investigated using the data on the orbital motion in waves, one was the characteristics of wave directional function and another was the nature of the wave force coefficient. The main conclusions obtained are as follows ;
Ocean waves have been observed with a wave height meter array and a three component current meter suspended from an ocean research platform. Directional spectra of measured waves are determined using the Maximum Likelyhood Method. The results obtained with these two sets of instruments were compared and investigations revealed the following ;
(a) representation of directional function due to Mitsuyasu et al., which was developed on the basis of the well developed wave data in mid-ocean, are in good agreement with that determined here form wave data collected near the coast and contained wide range of the development stage.
(b) time series of wind speed, significant value of wave height and spreading parameter Smax at the pe
ak frequency were in good mutual relation, and the value of Smax may be estimated practically from the significant value of wave height.
(c) measured values of the characteristics regarding the angular spreading of wave energy obtained with the wave height meter array and three-component current meter showed good agreement.
The wave forces were measured with two 2-component dynamometers set at either end of the test cylinder. The following was found.
(d) the values of Cp and CH obtained from least squares fit of the complete force time series of a random wave record were well ordered as a function of Keulegan-Carpenter number K2 defined by significant orbital displacement and the diameter of the cylinder, but those determined by the least squares fit on a wave-by-wave basis were widely scattered.
(e) ocean wave force exerted on the cylinder was well represented by Morison's formula ; the ratio of predicted wave force by this formula to the directly measured force was 90%, and the ratio was very stable throughout the experiments. Less
Research Output (9results)