Journal of Applied Science and Engineering

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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.

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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.

  1. [1] A. D’Ippolito, F. Calomino, G. Alfonsi, and A. Lauria, (2021) “Flow Resistance in Open Channel Due to Vegetation at Reach Scale: A Review" Water 13(2): DOI: 10.3390/w13020116.
  2. [2] F.-s. Wu, (2008) “Characteristics of flow resistance in open channels with non-submerged rigid vegetation" Journal of Hydrodynamics, Ser. B 20(2): 239–245. DOI: 10.1016/S1001-6058(08)60052-9.
  3. [3] F.-f. Gu, H.-g. Ni, and D.-m. Qi, (2007) “Roughness coefficient for unsubmerged and submerged reed" Journal of Hydrodynamics 19(4): 421–428. DOI: 10.1016/S1001-6058(07)60135-8.
  4. [4] K. R. Gubashi, S. Mulahasan, M. A. Jameel, and A.-S. T. Al-Madhhachi, (2022) “Evaluation drag coefficients for circular patch vegetation with different riverbed roughness" Cogent Engineering 9(1): 2044574. DOI: 10.1080/23311916.2022.2044574.
  5. [5] E.-q. Hui, X.-e. Hu, C.-b. Jiang, Z.-d. ZHU, et al., (2010) “A study of drag coefficient related with vegetation based on the flume experiment" Journal of Hydrodynamics, Ser. B 22(3): 329–337. DOI: 10.1016/S1001-6058(09)60062-7.
  6. [6] J.-t. Zhang and X.-h. Su, (2008) “Numerical model for flow motion with vegetation" Journal of Hydrodynamics 20(2): 172–178. DOI: 10.1016/S1001-6058(08)60043-8.
  7. [7] C. W. Li and C. Zeng, (2009) “3D Numerical modelling of flow divisions at open channel junctions with or without vegetation" Advances in Water Resources 32(1): 49– 60. DOI: 10.1016/j.advwatres.2008.09.005.
  8. [8] P.-f. Wang and C. Wang, (2011) “Numerical model for flow through submerged vegetation regions in a shallow lake" Journal of Hydrodynamics 23(2): 170–178. DOI: 10.1016/S1001-6058(10)60101-1.
  9. [9] M. M. Larmaei and T.-F. Mahdi, (2012) “Depthaveraged turbulent heat and fluid flow in a vegetated porous medium" International journal of heat and mass transfer 55(4): 848–863. DOI: 10.1016/j.ijheatmasstransfer.2011.10.023.
  10. [10] S. A. Mattis, C. N. Dawson, C. E. Kees, and M. W. Farthing, (2012) “Numerical modeling of drag for flow through vegetated domains and porous structures" Advances in Water Resources 39: 44–59.
  11. [11] S. Mulahasan, F. M. Al-Mohammed, and A.-S. T. AlMadhhachi, (2021) “Effect of blockage ratio on flow characteristics in obstructed open channels" Innovative Infrastructure Solutions 6(4): 211. DOI: 10.1007/s41062-021-00592-z.
  12. [12] T. R. Al-Husseini, A.-S. T. Al-Madhhachi, and Z. A. Naser, (2020) “Laboratory experiments and numerical model of local scour around submerged sharp crested weirs" Journal of King Saud UniversityEngineering Sciences 32(3): 167–176. DOI: 10.1016/j.jksues.2019.01.001.
  13. [13] S. S. Muhsun, A.-S. T. Al-Madhhachi, and Z. T. AlSharify, (2020) “Prediction and CFD simulation of the flow over a curved crump weir under different longitudinal slopes" International Journal of Civil Engineering 18(9): 1067–1076. DOI: 10.1007/s40999-020-00527-2.
  14. [14] P. Gualtieri, S. De Felice, V. Pasquino, and G. P. Doria, (2018) “Use of conventional flow resistance equations and a model for the Nikuradse roughness in vegetated flows at high submergence" Journal of Hydrology and Hydromechanics 66(1): 107–120. DOI: 10.1515/johh2017-0028.
  15. [15] P. Naden, P. Rameshwaran, O. Mountford, and C. Robertson, (2006) “The influence of macrophyte growth, typical of eutrophic conditions, on river flow velocities and turbulence production" Hydrological Processes: An International Journal 20(18): 3915–3938. DOI: 10.1002/hyp.6165.
  16. [16] F. Liwei, H. Reti, W. Wenxing, L. Zexiang, and Y. Zhiming, (2008) “Application of computational fluid dynamic to model the hydraulic performance of subsurface flow wetlands" Journal of Environmental Sciences 20(12): 1415–1422. DOI: 10.1016/S1001-0742(08)62542-5.
  17. [17] H. Cui, S. Felder, and M. Kramer, (2023) “Predicting flow resistance in open-channel flows with submerged vegetation" Environmental Fluid Mechanics: 1–22. DOI: 10.1007/s10652-023-09929-x.
  18. [18] F. López and M. H. García, (2001) “Mean flow and turbulence structure of open-channel flow through nonemergent vegetation" Journal of Hydraulic Engineering 127(5): 392–402. DOI: 10.1061/(ASCE )0733-9429(2001)127:5(392).
  19. [19] A. Defina and A. C. Bixio, (2005) “Mean flow and turbulence in vegetated open channel flow" Water Resources Research 41(7): DOI: 10.1029/2004WR003475.
  20. [20] C. Wilson, O. Yagci, H.-P. Rauch, and N. Olsen, (2006) “3D numerical modelling of a willow vegetated river/floodplain system" Journal of hydrology 327(1- 2): 13–21. DOI: 10.1016/j.jhydrol.2005.11.027.
  21. [21] T. Helmiö, (2002) “Unsteady 1D flow model of compound channel with vegetated floodplains" Journal of Hydrology 269(1-2): 89–99. DOI: 10.1016/S0022-1694(02)00197-X.
  22. [22] T. Fischer-Antze, T. Stoesser, P. Bates, and N. Olsen, (2001) “3D numerical modelling of open-channel flow with submerged vegetation" Journal of Hydraulic Research 39(3): 303–310. DOI: 10.1080/00221680109499833.
  23. [23] T. Stoesser, G. P. Salvador, W. Rodi, and P. Diplas, (2009) “Large eddy simulation of turbulent flow through submerged vegetation" Transport in porous media 78: 347–365. DOI: 10.1007/s11242-009-9371-8.
  24. [24] I. Nezu and M. Sanjou, (2008) “Turburence structure and coherent motion in vegetated canopy open-channel flows" Journal of hydro-environment research 2(2): 62–90. DOI: 10.1016/j.jher.2008.05.003.
  25. [25] T.-a. Okamoto and I. Nezu, (2010) “Large eddy simulation of 3-D flow structure and mass transport in openchannel flows with submerged vegetations" Journal of Hydro-environment Research 4(3): 185–197. DOI: 10.1016/j.jher.2010.04.015.
  26. [26] Z.-X. Xu, C. Ye, Y.-Y. Zhang, X.-K. Wang, and X.-F. Yan, (2020) “2D numerical analysis of the influence of near-bank vegetation patches on the bed morphological adjustment" Environmental Fluid Mechanics 20: 707–738. DOI: 10.1007/s10652-019-09718-5.
  27. [27] M. Shivashankar, M. Pandey, and A. K. Shukla, (2023) “Numerical Investigation on the Evaluation of the Sediment Retention Efficiency of Invert Traps in an Open Rectangular Combined Sewer Channel" Journal of Hazardous, Toxic, and Radioactive Waste 27(1): 04022045. DOI: 10.1061/(ASCE)HZ.2153-5515.0000733.
  28. [28] H. Tariq, U. Ghani, N. Anjum, and G. A. Pasha, (2022) “3D numerical modeling of flow characteristics in an open channel having in-line circular vegetation patches with varying density under submerged and emergent flow conditions" Journal of Hydrology and Hydromechanics 70(1): 128–144.
  29. [29] M. Kazem, H. Afzalimehr, and J. Sui, (2021) “Characteristics of turbulence in the downstream region of a vegetation patch" Water 13(23): 3468. DOI: 10.3390/w13233468.
  30. [30] J. Zhang, S. Zhang, C. Wang, W. Wang, and L. Ma, (2022) “Flow characteristics of open channels based on patch distribution of partially discontinuous rigid combined vegetation" Frontiers in Plant Science 13: 976646. DOI: 10.3389/fpls.2022.976646.
  31. [31] J. Qu and J. Yu, (2021) “A numerical modelling of flows in an open channel with emergent vegetation" Journal of Hydraulic Research 59(2): 250–262. DOI: 10.1080/00221686.2020.1770877.
  32. [32] W.-Y. Chang, G. Constantinescu, and W. F. Tsai, (2017) “On the flow and coherent structures generated by a circular array of rigid emerged cylinders placed in an open channel with flat and deformed bed" Journal of Fluid Mechanics 831: 1–40. DOI: 10.1017/jfm.2017.558.
  33. [33] Z. Chen, A. Ortiz, L. Zong, and H. Nepf, (2012) “The wake structure behind a porous obstruction and its implications for deposition near a finite patch of emergent vegetation" Water Resources Research 48(9): DOI: 10.1029/2012WR012224.
  34. [34] O. Bilhan, M. C. Aydin, M. E. Emiroglu, and C. J. Miller, (2018) “Experimental and CFD analysis of circular labyrinth weirs" Journal of Irrigation and Drainage Engineering 144(6): 04018007. DOI: 10.1061/(ASCE)IR.1943-4774.0001301.
  35. [35] H. M. Nepf, (1999) “Drag, turbulence, and diffusion in flow through emergent vegetation" Water resources research 35(2): 479–489. DOI: 10.1029/1998WR900069.
  36. [36] W.-q. Li, D. Wang, J.-l. Jiao, and K.-j. Yang, (2019) “Effects of vegetation patch density on flow velocity characteristics in an open channel" Journal of Hydrodynamics 31(5): 1052–1059. DOI: 10.1007/s42241-018-0086-6.
  37. [37] U. Ghani, N. Anjum, G. A. Pasha, and M. Ahmad, (2019) “Investigating the turbulent flow characteristics in an open channel with staggered vegetation patches" River Research and Applications 35(7): 966–978. DOI: 10. 1002/rra.3460. [38] L. Zong and H. Nepf, (2012) “Vortex development behind a finite porous obstruction in a channel" Journal of Fluid Mechanics 691: 368–391. DOI: 10.1017/jfm.2011.479.