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中文核心期刊

沿岸流不稳定多模式运动的理论分析

The theoretical analysis on multi-mode of the instability of longshore currents

  • 摘要: 目前对沿岸流不稳定研究比较成熟的理论基础是线性不稳定理论,该理论假定增长率最大的不稳定模式决定着沿岸流的波动特性,但实验分析结果表明对有些情况下该假定难以解释实验中观测到的情况.利用沿岸流不稳定运动的多模式理论分析了实验中观测到的情况.结果表明沿岸流速度剖面对于沿岸流不稳定运动模式影响很大,特别是速度剖面的变化会导致不稳定模式出现多个模式的情况,即增长率曲线出现多于两个峰的情况.用解析的速度剖面分析了速度剖面前剪切和后剪切同时变化及单独变化对于沿岸流不稳定多模式运动的影响.结果表明对于坡度为1:100的平直斜坡的情况用前剪切不稳定理论可以解释其观测到的现象.

     

    Abstract: Thepopular theory for the instability of longshore currents is thelinear shear instability theory. It is assumed that theinstability mode with the largest growth rate dominates theinstability of longshore currents. However, the assumption cannotbe used to some case from the experimental results. In the presentpaper, milti-mode unstable process (or behavior) has been analyzedwhich is in good agreement with our previous experiment results.Velocity profile has great effects on the growth mode of theinstability of longshore currents. Specially, variations can leadto multi-mode of the instability of longshore currents, viz. morethan two peaks occur in growth rate curve. In present paper, weanalyze the effect of frontshear and backshear simultaneousvariations and individually of the both on the multi-mode of theinstability of longshore currents using analytic velocityprofiles. The analysis shows that the wave development(orphenomena, formation,evolution) in our experiment can beattributed to the frontshear instability.

     

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