Hydraulic jump morphology and dynamics on beds roughened by rigid and flexible vegetation
摘要
Interaction of hydraulic jumps with rough beds was investigated extensively for engineered stilling basin floors equipped with rigid roughness elements, while the effects of flexible vegetation roughness that is commonly encountered in natural waterways remain unclear. This study investigates rough-bed hydraulic jumps across six vegetation bed configurations, including both rigid and flexible vegetation types of comparable equivalent roughness heights, for Froude numbers ranging from 2.8 to 5.9 and Reynolds numbers in the order of 105. The free-surface profiles and fluctuation features are measured, and the impacts of vegetation types, equivalent roughness heights and flow Froude numbers on the morphological features are analyzed. The results indicate that the upward roller motion induced by the jump-vegetation interaction significantly modifies the jump morphology over rough beds. The flow and vegetation interact at varying intensities, which can be assessed with the aid of the self-similarity in surface profile. The analysis reveals different evolutionary relations between the free-surface characteristics and Froude number for the tested bed conditions. The findings highlight complex morphological features of flexible-vegetation-bed hydraulic jumps, which cannot be simplistically predicted based on the conclusions deriving from observations of hydraulic jumps over rigid rough beds.