FLOW CHARACTERISTICS IN OPEN-CHANNEL FLOWS WITH STRONG UNSTEADINESS

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  • NEZU Iehisa
    社団法人 土木学会 京都大学大学院 環境地球工学専攻
  • ONITSUKA Kouki
    社団法人 土木学会 京都大学大学院 環境地球工学専攻

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  • 強い非定常性を受ける開水路乱流の平均流特性
  • ツヨイ ヒテイジョウセイ オ ウケル カイスイロ ランリュウ ノ ヘイキンリュウ トクセイ

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Abstract

Turbulence measurements in open-channel flows with strong unsteadiness were conducted with a two component laser Doppler anemometer (LDA). The water-surface fluctuations at three points were measured by making use of 3 sets of ultrasonic wave gauges. It was found that the Karman constant κ can be dealt with as a universal constant (κ=0.41) in the case that the unsteadiness parameter α is smaller than 0.002. In contrast, the integration constant A of the log-law changes in a complicated manner. The time-dependent property of each term in the momentum equation (4) was examined on the basis of experimental data. The gravity term is smaller than the pressure and acceleration terms. The pressure term has an effect of increase upon the bed-shear stress τb in the rising stage, and vise versa in the falling stage. On the other hand, the unsteady term has the opposite effect to the pressure term.

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