Influence of Vegetation on Shear Stress and Flow Rate in Open Channel using Flow3D

Abstract

Flood accidents account for approximately one-third of all financial losses worldwide. Analysis of the trend of accidents shows that in recent years such incidents have increased dramatically. In recent years, river engineers have been looking for a suitable solution to reduce the impact of floods. The critical role of floodplains in flood relief is significant and their reconstruction is being promoted [1]. The hydraulic flow exchange between the river channel and its floodplain is complex. In a relatively high discharge that engulfs the adjacent floodplain, the exchange of flow between the main channel and the floodplain results in rotational currents [2]. Traditionally, the presence of vegetation on the floodplain as a problem that disrupts flow capacity has been the focus of river engineers [3]. The presence of vegetation in the floodplains adds a degree of complexity to the analysis of composite channel flows and the amount of drag force applied by the flow to the plant cannot be ignored. Observing the riverbanks shows that plant growth in a row on the edge of a flood plain is a common arrangement [4]. A range of coastal plants may be used for shore sustainability, promoting environmental diversity or for creating scenic landscapes. Hubble [5] et al. Knowledge about the impact of vegetation on the flow structure is scarce at present. In order to achieve simultaneous protection against floods and environmental requirements, better awareness of the hydraulic flow in composite channels with vegetation is required. High-momentum rotational currents transmit the current from the main channel to the floodplain, which results in a decrease in transmission in the main channel and its increase near the floodplain. This phenomenon is known as the kinematic effect [6]. The relative depth of Dr is defined as the ratio of the flow depth in the floodplain (Hfp) to the water depth in the main channel (Hmc) [7]. Strong exchange was observed at a relative depth between 0.1 and 0.3 [8]. In composite channels like simple straight channels, rotational currents are caused by non-isotropic perturbations and their properties are influenced by many factors such as channel transverse geometry, shape ratio, relative depth and turbulence value. Tominaga and Nezu [9] performed experiments on a rectangular composite channel and concluded that the size and position of secondary flows were highly dependent on channel geometry [10]. The researchers identified a weak secondary current in the main channel and floodplain at a relative depth of Dr = 0.5, and a rotational current near the free surface of the current along the side wall of the main channel [11].