| 振荡流层移输沙条件下悬沙层泥沙扩散系数垂向分布特征研究 |
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| 引用本文： | 谭泽宇,刘海江.振荡流层移输沙条件下悬沙层泥沙扩散系数垂向分布特征研究[J].海洋工程,2019,37(4):35-44. |
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| 作者姓名： | 谭泽宇 刘海江 |
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| 作者单位： | 浙江大学海洋学院;浙江大学建筑工程学院 |
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| 基金项目： | 国家重点研发计划资助项目（2017YFC0405401）；浙江省自然科学基金项目（LZ19E090001） |
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| 摘 要： | 层移输沙是海岸带泥沙运动的主要形式之一,其垂向悬沙浓度分布规律的研究一直是海岸工程关心的重点。一般情况下,经典的纯扩散模型被用来描述和解释悬沙浓度的试验数据,该模型认为周期平均悬沙浓度主要由参考浓度、泥沙沉速和泥沙扩散系数确定。泥沙扩散系数可以由泥沙沉速和悬沙浓度的垂向梯度反演得到。既往研究大多直接给出泥沙扩散系数的结果,对于不同反演计算方法间结果差别的研究较少。本研究汇总了已有振荡流层移输沙试验数据,采用曲线拟合方法和直接差分方法计算了相应的泥沙扩散系数,研究表明两种方法得到的计算结果在垂向位置z 0.15 m处差异不大,随着垂向位置的升高,差分方法的计算结果略微大于拟合方法。考虑到拟合方法可以得到连续的泥沙扩散系数垂向分布,本研究推荐使用幂函数形式的曲线拟合方法求解悬移泥沙扩散系数。基于此,对比分析了层移输沙悬沙层泥沙扩散系数随泥沙粒径、振荡流周期、均方根流速和振荡流类型等物理参数的变化规律。在纯振荡流层移输沙条件下,泥沙扩散系数随泥沙粒径的增大而增大,而振荡流周期和均方根流速几乎不影响泥沙扩散系数。在振荡流和定常流共同作用下,泥沙扩散系数受振荡流周期和定常流流速的影响,泥沙扩散系数随着振荡流周期的增大或定常流流速的减小而增大。
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| 关 键 词： | 泥沙扩散系数 层移输沙 曲线拟合方法 直接差分方法 悬沙浓度 振荡流 |
Study of vertical distribution of the sediment diffusion coefficient in suspended layer under the oscillatory sheet flow condition |
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| TAN Zeyu and LIU Haijiang.Study of vertical distribution of the sediment diffusion coefficient in suspended layer under the oscillatory sheet flow condition[J].Ocean Engineering,2019,37(4):35-44. |
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| Authors: | TAN Zeyu and LIU Haijiang |
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| Institution: | Ocean College, Zhejiang University, Hangzhou 310058, China and College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China |
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| Abstract: | Sheet flow regime is one of the main sediment movement patterns in coastal zone. Suspended sediment transport plays a significant role in studying the coastal sediment movement. In general, the traditional pure diffusion model is used to describe and interpret the existing experimental data. Accordingly, time-averaged suspended sediment concentration depends on the reference concentration, settling velocity and sediment diffusivity. Consequently, sediment diffusivity can be obtained using the sediment setting velocity and the vertical distribution of time-averaged suspended sediment concentration. However, most of the previous studies directly present the results of the sediment diffusivity, without comparing the differences among various calculation methods. In this study, the difference between the curve-fitting method and the direct-difference method is investigated. It is confirmed that difference between these two methods is trivial when vertical elevation is smaller than 0.15m. To obtain a continuous vertical distribution of sediment diffusivity, it is recommended to use the curve-fitting method. In addition, effects of grain size, oscillatory flow period, the root-mean-squared (RMS) oscillatory flow velocity and oscillatory flow type on the sediment diffusivity are also discussed. Under the pure oscillatory flow condition, the larger the grain size is, the larger the sediment diffusivity is. Nevertheless, both oscillatory flow period and RMS flow velocity hardly affect the sediment diffusivity. Under the combined oscillatory flow and current condition, sediment diffusivity however is affected by the oscillatory flow period and current velocity. The longer the oscillatory flow period or the smaller the current velocity is, the larger the sediment diffusivity is. |
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| Keywords: | sediment diffusivity sheet flow curve-fitting method direct-difference method sediment concentration oscillatory flow |
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