Drag coefficient for rigid vegetation in subcritical open-channel flow

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.