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Title: 風波上を通過する気流の3次元直接数値計算
Other Titles: Direct numerical simulation of turbulent airflow over traveling wind waves
Authors: 木原, 直人  KAKEN_name
植田, 洋匡  KAKEN_name
花崎, 秀史  KAKEN_name
Author's alias: KIHARA, Naoto
UEDA, Hiromasa
Keywords: 風波
turbulent flow
air-sea interaction
boundary layer
direct numerical simulation
Issue Date: 1-Apr-2005
Publisher: 京都大学防災研究所 / Disaster Prevention Research Institute Kyoto University
Journal title: 京都大学防災研究所年報. B = Disaster Prevention Research Institute annuals. B
Volume: 48
Issue: B
Start page: 541
End page: 550
Abstract: 一定の位相速度で進行する風波上の気流に3次元直接数値計算を適用することにより,気流の乱流特性を調べた。7種類の波齢( c /u* =0, 4, 8, 10, 12, 16 and 20)で,それぞれについて乱流が統計的に定常状態になるまで計算した。その結果,気流及び乱流の挙動に強い波齢依存性が見られた。また,波によりゆがまされた流れは,臨界高さ近傍で大きく変化した。その結果,波の発達率と強い関係がある波による運動量フラックス(wave-induced momentum flux)は臨界高さより低い場所では正,高い場所では負となることがわかった。
Characteristics of the airflow over a train of waves moving at a constant speed are investigated using a direct numerical simulation. We simulate the flow for various wave ages ( c /u* =0, 4, 8, 10, 12, 16 and 20), where c is the phase speed of the wind wave and u* is the friction velocity on the wave surface. The results show that both the mean flow profiles and the turbulent statistics depend strongly on the wave age. For example, the mean-flow speed in the log layer generally decreases at small wave ages, I. E., when the wave growth rate is positive. Vertical profiles of the flow change significantly at the critical height zc , where the mean flow speed and the wave speed c agree. Then, the wave-induced vertical flux of the horizontal momentum is positive below zc , decreases rapidly near zc , and becomes negative above zc .
Appears in Collections:No.48 B

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