Laboratory investigation of flow behavior in an open channel with emerged porous rigid and flexible vegetation

Abstract

This study aims to investigate the influence of various vegetation patches with varying porosities on the hydraulic properties of a vegetated open channel under subcritical flow conditions. This research work investigated three types of vegetation patches: Rigid, flexible, and a combination of the two. In total five vegetation patches with three different porosities for each patch were investigated. Effect of these vegetation patches on various hydraulic parameters such as backwater rise, energy reduction, water surface slope in the vegetation patch, hydraulic jump formation on the downstream side of the vegetation patch, reduction in fluid force index (RFI), moment index (RMI), overflow volume (ΔQ) were studied. The findings revealed that the backwater rise increased in the case of rigid patch as the initial Froude number increased, whereas it decreased in the case of flexible and combined vegetation patches. It was observed that as the porosity increased from low (P_r = 0.90) to high (P_r = 0.99), the backwater rise decreased for all vegetation patches. The relative energy reduction rate increased for the rigid patch and showed a reverse trend for the flexible and combined vegetation patches with increasing initial Froude number. In the combined vegetation arrangement, the energy reduction values were highest for the alternate rigid and flexible (ARF) vegetation patches and lowest for the longitudinal rigid and flexible (LRF) vegetation patches. This study identified the presence of a hydraulic jump downstream of the vegetation patch, as indicated by the Froude number in the range of 1.0–1.7. The study also found that RFI, RMI, ΔQ had the highest values of 19.05%, 19.05%, 80.20%. The results of this study provide insight into the impact of vegetation patches with varying porosities on open-channel flow characteristics and can help develop sustainable vegetation management strategies.