Drag coefficient for rigid vegetation in subcritical open-channel flow |
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Authors: | Xiaoguang?Liu Email author" target="_blank">Yuhong?ZengEmail author |
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Institution: | 1.State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan,China |
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Abstract: | Drag coefficient has been commonly used as a quantifying parameter to represent the vegetative drag, i.e., resistance to the flow by vegetation. In this study, the measured data on the drag coefficient for rigid vegetation in subcritical open-channel flow reported in previous studies are collected and preprocessed for multi-parameter analysis. The effect of Froude number (Fr) on the drag coefficient for rigid vegetation in subcritical flow cannot be ignored, especially when \(Fr < 0.12\). The drag coefficient is observed to exponentially decrease with the stem Reynolds number (R d ) and logarithmically decreased with the vegetation density (λ) when \(0.012 < \lambda < 0.12\). The relative submergence (h * ) has a significant effect on the drag coefficient, and a positive logarithmic relationship is summarized. A simplified three-stage empirical formula is obtained based on the divisions of Fr. Laboratory tests (with \(Fr < 0.02\)) prove that the present empirical model has higher precision compared with existing models. |
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