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Effects of Roughness Reynolds Number on Scalar Transfer Mechanisms at the Sediment-Water Interface

机译：雷诺数对沉积物-水界面标量传递机制的影响

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摘要

The passive scalar transport across a sediment-water interface (SWI) is of fundamental importance to river environments. A model for scalar transfer from water to organic sediment bed is developed. The bed is formed by packed particles so that combined effect of permeability and roughness can be considered. Large-eddy simulation is used to get spatial and temporal information. The numerical results are compared to data from laboratory experiments, which stress the importance of considering bed roughness to better characterize the turbulent diffusion across the SWI. From the smooth regime to the transitionally regime, the turbulent diffusion exceeds the molecular diffusion and the dominating role at the interface changes from molecular diffusion to turbulent diffusion. In the completely rough regime, the molecular diffusive flux can be ignored compared with the turbulent flux. Moreover, turbulent Schmidt number is found to be higher near the SWI and lower around the middle of flow depth, ranging from 0.5 to 1. The results will be helpful to design the parameterization for the scalar transport over streams, rivers, or coastal areas where flow near the bed surface is relatively high and hyporheic exchange is affected by roughness and bed permeability.
机译：穿过沉积物-水界面（SWI）的被动标量传输对于河流环境至关重要。建立了从水到有机沉积床的标量转移模型。该床是由堆积的颗粒形成的，因此可以考虑渗透率和粗糙度的综合作用。大涡模拟用于获取空间和时间信息。将数值结果与来自实验室实验的数据进行了比较，这些数据强调了考虑床粗糙度以更好地表征整个SWI湍流扩散的重要性。从光滑状态到过渡状态，湍流扩散超过了分子扩散，界面处的主导作用从分子扩散变为湍流扩散。在完全粗糙的状态下，与湍流相比，分子扩散通量可以忽略不计。此外，发现湍流的施密特数在SWI附近较高，在流动深度的中部较低，范围从0.5到1。该结果将有助于设计在河流，河流或沿海地区的标量运输的参数化床表面附近的水流相对较高，粗糙度和床渗透性会影响水交换。

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  • 来源
    《Water resources research》 |2019年第8期|6811-6824|共14页
  • 作者

    He G. J.; Han X.; Fang H. W.; Reible D.; Huang L.;

  • 作者单位

    Tsinghua Univ Dept Hydraul Engn State Key Lab Hydro Sci & Engn Beijing Peoples R China;

    Texas Tech Univ Dept Civil & Environm Engn Lubbock TX 79409 USA;

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