Grant-in-Aid for Scientific Research (A)
|Allocation Type||Single-year Grants |
|Research Institution||Kyushu University |
MASUDA Akira Kyushu University, Research Institute for Applied Mechanics, Prof, 応用力学研究所, 教授 (60091401)
YASUDA Takashi Kyushu University, Faculty of Engineering, Prof, 工学部, 教授 (10093329)
MATSUNAGA Nobuhiro Kyushu University, Interdisciplinary Graduate School, Prof, 総合理工学研究院, 教授 (50157335)
KARASUDANI Takashi Kyushu University, Research Institute for Applied Mechanics, Assoc.Prof, 応用力学研究所, 助教授 (30150527)
UENO Koji Meteorological College, Assoc.Prof, 気象大学校, 助教授
TANAKA Mitsuhiro Kyushu University, Faculty of Engineering, Prof, 工学部, 教授 (70163582)
草場 忠夫 九州大学, 応用力学研究所, 助教授 (00037871)
|Project Period (FY)
2000 – 2003
Completed (Fiscal Year 2003)
|Budget Amount *help
¥41,990,000 (Direct Cost: ¥35,000,000、Indirect Cost: ¥6,990,000)
Fiscal Year 2003: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
Fiscal Year 2002: ¥9,230,000 (Direct Cost: ¥7,100,000、Indirect Cost: ¥2,130,000)
Fiscal Year 2001: ¥18,200,000 (Direct Cost: ¥14,000,000、Indirect Cost: ¥4,200,000)
Fiscal Year 2000: ¥11,700,000 (Direct Cost: ¥11,700,000)
|Keywords||breaking of wind-waves / surface coverage of white cap / swell effect on wind-waves / sea surface flux of CO2 / numerical simulation of waves / sea surface roughness and drag coefficient / turbulence beneath the sea surface / spectral evolution of wind-waves and swell / 風波の破砕と側帯波不安定 / 海面境界過程と物質輸送 / 水中・気中の二酸化炭素濃度 / 水面下のラグランジュ循環流 / 風洞水槽実験 / 風波のスペクトル発展 / 大気境界層と海面下の乱流 / 水面下のラングミュア循環 / 現地海洋観測 / 大気境界と海面下の乱流|
1.[swell and wind-waves]
(1)Swell propagating with wind is known to suppress the growth of wind-waves. The suppression rate calculated based on the recently proposed hypothesis of Chen and Belcher was found to agree well with the result of the laboratory experiment, though careful verification is necessary. (2)A new term of swell dissipation was introduced to the operating MRI wave model. This term proved to much improve the accuracy of wave prediction off Hawaii in the Pacific, where most wave models have failed to predict the swell well so far.
2.[wave breaking and water turbulence]
(1)The surface flow was observed in a thin layer that is about twice as thick as the significant wave height under strong wind and intense wave breaking. A new model of the vertical distribution of surface flow was proposed based on that measurement. (2)As regards the dissipation of wave energy, a simple model of wave breaking was incorporated into a numerical model for the direct numerical simulation of irr
otational waves. That model yielded an estimate of energy dissipation that is compared favorably with laboratory experiments and wave prediction models.
Wave breaking is detected by a visible phenomenon of "whitecap". Based on the observation under various wind-sea conditions, whitecap coverage was confirmed to increase rapidly with the third power of wind velocity. Also whitecap coverage was found relatively high for (1)unstable density stratification, (2)decaying waves, and (3)wind-waves unaffected by swell.
4.[CO2 concentration and flux ]
(1)Daily variation and regional characteristics of atmospheric CO2 concentration was observed at Tsushima and Shikanoshima in the Eastern Tsushima Strait. (2)It was pointed out that correction due to the effect of vapor and temperature is necessary when eddy-correlation method is used to measure the CO2 flux in summer. (3)In a wind flume, CO2 flux across the water surface was measured accurately. Gas exchange velocity was found to depend not only on the wind velocity, but also on the fetch and a new empirical formula was proposed to express the fetch-dependence of the gas exchange velocity.
5.[momentum flux : wave effect on the drag coefficient and roughness length of sea surface]
(1) A non-dimensional formula of the roughness of water surface waves that takes into account surface tension and viscosity was proposed based on laboratory experiments of high accuracy. (2)Momentum flux above the sea surface was measured at a sea station by simultaneous application of eddy-correlation, inertial dissipation and, profile methods in order to guarantee the reliability. Then a new comprehensive formula was proposed to explain the various previous formulas of roughness length that have seemed even contradictory with one another, in particular as regards the dependence on wind-waves. Less