Velocity distribution in trapezoidal meandering channel

Abstract

Analysis of fluvial flows are strongly influenced by geometry complexity and large overall uncertainty on every single measurable property, such as velocity distribution on different sectional parameters like width ratio, aspect ratio and hydraulic parameter such as relative depth. The geometry selected for this study is that of a smooth sine generated trapezoidal main channel flanked on both sides by wide flood plains. The parameters which were changed in this research work include the overbank flow depth, main channel flow depth, incoming discharge of the main channel and floodplains. This paper presents a practical method to predict lateral depth-averaged velocity distribution in trapezoidal meandering channels. Flow structure in meandering channels is more complex than straight channels due to 3-Dimentional nature of flow. Continuous variation of channel geometry along the flow path associated with secondary currents makes the depth averaged velocity computation difficult. Design methods based on straight-wide channels incorporate large errors while estimating discharge in meandering channel. Hence based on the present experimental results, a nonlinear form of equation involving 3 parameters for estimating lateral depth-averaged velocity is formulated. The present experimental meandering channel is wide (aspect ratio = b/h > 5) and with high sinuosity of 2.04. A quasi1D model Conveyance Estimation System (CES) was then applied in turn to the same compound meandering channel to validate with the experimental depth averaged velocity. The study serves for a better understanding of the flow and velocity patterns in trapezoidal meandering channel. A commercial code, ANSYS-CFX 13.0 is used to simulate a 60 meander channel using Large Scale Eddy (LES) model. Contours regarding the velocities in three directions are derived.