Authors: Muhammad Mujahid Muhammad, Khamaruzaman Wan Yusof, Muhammad Raza Ul Mustafa, Aminuddin Ab. Ghani
Studying the velocity distributions in grassed channel such as swale can help in proper design of eco-friendly channel against erosion. To understand the hydrodynamics of vegetated channel, previous studies make use of artificial vegetation to perform laboratory experiments, and this has been challenged by several researches. The present study employed the use of natural submerged vegetation to investigate the velocity distribution within a grassed flume. To achieve this, velocity profiles were measured using Acoustic Doppler Velocimeter (ADV) in order to obtain the stream-wise and vertical velocity profiles along several vertical and cross sections. Evaluation of the experimental results revealed that the velocity profile was not uniformly distributed in channel infested by submerged grass; and the velocity distribution is greatly influenced by the vegetation density. It can be concluded that for a submerged flexible vegetation the velocity profiles for both stream-wise and verticals are being influenced by the grass roughness, geometry and the flow depth. From the results, it was found that the flow depth of 0.15 m has wider velocity range compared to the other depths of 0.20 m and 0.40 m respectively, with the 0.40 m depth having the least velocity range.
Keywords: Velocity distributions; Natural vegetation; Submerged vegetation; ADV; Stream-wise velocity; Vertical velocity