A numerical model to evaluate flow characteristics in a circular vegetation patch for flume experiments

Karim R.  Gubashi; Shaymaa A.  Al-Hashimi; Saad  Mulahasan; Abdul-Sahib T.  Al-Madhhachi

doi:10.6180/jase.202501_28(1).0008

A numerical model to evaluate flow characteristics in a circular vegetation patch for flume experiments

Karim R. GubashiThis email address is being protected from spambots. You need JavaScript enabled to view it., Shaymaa A. Al-Hashimi, Saad Mulahasan, and Abdul-Sahib T. Al-Madhhachi

Mustansiriyah University, College of Engineering, Department of Water Resources Engineering, Iraq

Received: December 10, 2023
Accepted: February 19, 2024
Publication Date: March 23, 2024

Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.6180/jase.202501_28(1).0008

A 2D numerical model was performed for the flume experiments to clarify the combined effect of the vegetation patches mimicked by circular cylinders attached vertically in a laboratory canal with different bed roughness on the flow characteristics. Eleven patches with numbers of cylinders were distributed uniformly at a distance of 0.20 m center-to-center along the flume length starting from 1.2 m from the flume entrance. The combined effect of the vegetation patch and bed materials on the drag coefficient Cd, the velocity distribution, and turbulent kinetic energy has been investigated using computational fluid dynamics. A mathematical model was established using the experimental data available in the literature. Results showed good agreement between the experimental and numerical drag coefficients by the vegetation patch and for the different bed roughness with a correlation coefficient of more than 99%. Results also showed a high correlation coefficient for all the laboratory experiments between Cd and n. One of the main problems with this type of flow is that vortices are strongly influenced by the adjacent cylinders downstream. Clear differences in velocity distribution and turbulent kinetic energy through the patches for the various bed materials have been monitored. The turbulent kinetic energy within the patch is increased by 2-3 times downstream of the patch. In this computational numerical domain, the simulation of the flow velocity in open channels with and without vegetation elements is well captured within and downstream of the patch and the wake by the individual cylinders.

Keywords: vegetated patch, drag coefficient, hydrodynamic model, computation fluid dynamics, flow properties.

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