Submerged rigid vegetation effects on flow hydrodynamics within the pool morphology

Abstract

This research is centered on a comprehensive investigation into the impact of turbulence on the movement and dispersion of materials within a threedimensional (3D) bedform, specifically when there is a continuous presence of rigid vegetation submerged in the flow. To achieve our research objectives, we conducted extensive velocity measurements within a channel featuring this submerged vegetation. The measurements were carried out using an Acoustic Doppler Velocimeter (ADV). Additionally, our study delved into the intricate structures and turbulent characteristics of the flow, considering the coexistence of submerged vegetation and a 3D gravel pool. This pool featured entrance and exit slopes measuring 3 and 2.5°, respectively. Our experimental setup took place in a straight flume, measuring 14 m in length, 0.9 m in width, and 0.6m in depth. The flume was equipped with transparent side walls to facilitate observations. Furthermore, our investigation extended to the spatial variations in velocity and turbulence distributions. We analyzed various parameters including turbulence kinetic energy, integral turbulence lengths, dispersion coefficients, and advective transport. The results revealed that integral length scales offer key insights into turbulent eddy behavior. In the presence of vegetation and a 3D bedform, turbulent eddies undergo notable changes, flattening in the longitudinal direction and expanding in the transverse and vertical directions. Moreover, longitudinal advection is notably higher compared to flows without vegetation in a uniform flow or bare channel, especially for z/H > 0.2. This indicates that the presence of vegetation and a 3D bedform leads to an increase in turbulent kinetic energy (k values) that surpasses the reduction in the time-averaged velocity component (“U”) in the U × k term, thereby enhancing longitudinal advection.

Keywords

3D pool / advection / dispersion / integral turbulent length / submerged rigid vegetation

References

[1] Afzalimehr, H., Barahimi, M., & Sui, J. (2019). Non-uniform flow over cobble bed with submerged vegetation strip. In Proceedings of the Institution of Civil Engineers-Water Management. Thomas Telford Ltd.

[2] Afzalimehr, H., Nosrati, K., & Kazem, M. (2021). Resistance to flow in a cobble-gravel bed river with irregular vegetation patches and pool-riffle bedforms (case study: Padena Marbor River). Ferdowsi Civil Engineering, 34(2), 35–50.

[3] Aris, R. (1956). On the dispersion of a solute in a fluid flowing through a tube. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 235(1200), 67–77.

[4] Ben Meftah, M., & Mossa, M. (2016). Partially obstructed channel: Contraction ratio effect on the flow hydrodynamic structure and prediction of the transversal mean velocity profile. Journal of Hydrology, 542, 87–100.

[5] Coceal, O., Dobre, A., Thomas, T. G., & Belcher, S. E. (2007). Structure of turbulent flow over regular arrays of cubical roughness. Journal of Fluid Mechanics, 589, 375–409.

[6] Cornacchia, L., van de Koppel, J., van der Wal, D., Wharton, G., Puijalon, S., & Bouma, T. J. (2018). Landscapes of facilitation: How self-organized patchiness of aquatic macrophytes promotes diversity in streams. Ecology, 99(4), 832–847.

[7] Costanza, R., d’Arge, R., de Groot, R., Farber, S., Grasso, M., Hannon, B., Limburg, K., Naeem, S., O’Neill, R. V., Paruelo, J., Raskin, R. G., Sutton, P., & van den Belt, M. (1997). The value of the world’s ecosystem services and natural capital. Nature, 387(6630), 253–260.

[8] Defina, A., & Bixio, A. C. (2005). Mean flow and turbulence in vegetated open channel flow. Water Resources Research, 41(7), 1–12.

[9] D’Ippolito, A., Calomino, F., Alfonsi, G., & Lauria, A. (2021). Flow resistance in open channel due to vegetation at reach scale: A review. Water, 13(2), 116.

[10] El Kadi Abderrezzak, K., Ata, R., & Zaoui, F. (2015). One-dimensional numerical modelling of solute transport in streams: The role of longitudinal dispersion coefficient. Journal of Hydrology, 527, 978–989.

[11] Fazlollahi, A., Afzalimehr, H., & Sui, J. (2015). Effect of slope angle of an artificial pool on distributions of turbulence. International Journal of Sediment Research, 30(2), 93–99.

[12] Ghisalberti, M., & Nepf, H. (2006). The structure of the shear layer in flows over rigid and flexible canopies. Environmental Fluid Mechanics, 6, 277–301.

[13] Ghisalberti, M., & Nepf, H. M. (2002). Mixing layers and coherent structures in vegetated aquatic flows. Journal of Geophysical Research: Oceans, 107(C2), 1–11.

[14] Ghisalberti, M., & Nepf, H. M. (2004). The limited growth of vegetated shear layers. Water Resources Research, 40(7), 1–12.

[15] Goring, D. G., & Nikora, V. I. (2002). Despiking acoustic Doppler velocimeter data. Journal of Hydraulic Engineering, 128(1), 117–126.

[16] Gurnell, A. (2014). Plants as river system engineers. Earth Surface Processes and Landforms, 39(1), 4–25.

[17] Kazem, M., Afzalimehr, H., & Sui, J. (2021). Characteristics of turbulence in the downstream region of a vegetation patch. Water, 13(23), 3468.

[18] Liu, D., Alobaidi, K., & Valyrakis, M. (2022). The assessment of an Acoustic Doppler Velocimetry profiler from a user’s perspective. Acta Geophysica, 70(5), 2297–2310.

[19] Marion, A., Zaramella, M., & Bottacin-Busolin, A. (2008). Solute transport in rivers with multiple storage zones: The STIR model. Water Resources Research, 44(10), 1–10.

[20] Mossa, M., Ben Meftah, M., De Serio, F., & Nepf, H. M. (2017). How vegetation in flows modifies the turbulent mixing and spreading of jets. Scientific Reports, 7(1), 6587.

[21] Naden, P., Rameshwaran, P., Mountford, O., & Robertson, C. (2006). The influence of macrophyte growth, typical of eutrophic conditions, on river flow velocities and turbulence production. Hydrological Processes, 20(18), 3915–3938.

[22] Nepf, H., & Ghisalberti, M. (2008). Flow and transport in channels with submerged vegetation. Acta Geophysica, 56, 753–777.

[23] Nepf, H. M. (1999). Drag, turbulence, and diffusion in flow through emergent vegetation. Water Resources Research, 35(2), 479–489.

[24] Nepf, H. M. (2012a). Flow and transport in regions with aquatic vegetation. Annual Review of Fluid Mechanics, 44, 123–142.

[25] Nepf, H. M. (2012b). Hydrodynamics of vegetated channels. Journal of Hydraulic Research, 50(3), 262–279.

[26] Nepf, H. M., Mugnier, C. G., & Zavistoski, R. A. (1997). The effects of vegetation on longitudinal dispersion. Estuarine, Coastal and Shelf Science, 44(6), 675–684.

[27] Nepf, H. M., & Vivoni, E. R. (2000). Flow structure in depth-limited, vegetated flow. Journal of Geophysical Research: Oceans, 105(C12), 28547–28557.

[28] Nikora, V. I., Stoesser, T., Cameron, S. M., Stewart, M., Papadopoulos, K., Ouro, P., McSherry, R., Zampiron, A., Marusic, I., & Falconer, R. A. (2019). Friction factor decomposition for rough-wall flows: Theoretical background and application to open-channel flows. Journal of Fluid Mechanics, 872, 626–664.

[29] Nordin, C. F., & Sabol, G. V. (1974). Empirical data on longitudinal dispersion in rivers. US Geological Survey.

[30] Nosrati, K., Afzalimehr, H., & Sui, J. (2022). Interaction of irregular distribution of submerged rigid vegetation and flow within a straight pool. Water, 14(13), 2036.

[31] Nosrati, K., Afzalimehr, H., Sui, J., & Reisifar, H. R. (2024). Characteristics of turbulent flow in 3-D pools in the presence of submerged rigid vegetation in channel bed. Journal of Hydrodynamics, 36, 158–169.

[32] Okubo, A. (1971). Oceanic diffusion diagrams, Deep sea research and oceanographic abstracts. Elsevier.

[33] Perucca, E., Camporeale, C., & Ridolfi, L. (2009). Estimation of the dispersion coefficient in rivers with riparian vegetation. Advances in Water Resources, 32(1), 78–87.

[34] Poggi, D., Krug, C., & Katul, G. G. (2009). Hydraulic resistance of submerged rigid vegetation derived from first-order closure models. Water Resources Research, 45(10), 1–14.

[35] Poggi, D., Porporato, A., Ridolfi, L., Albertson, J. D., & Katul, G. G. (2004). The effect of vegetation density on canopy sub-layer turbulence. Boundary-Layer Meteorology, 111, 565–587.

[36] Rubol, S., Battiato, I., & de Barros, F. P. J. (2016). Vertical dispersion in vegetated shear flows. Water Resources Research, 52(10), 8066–8080.

[37] Schlichting, H., & Gersten, K. (1979). Boundary-Layer Theory. MacGraw Hill.

[38] Schultz, R. C., Collettil, J. P., Isenhart, T. M., Simpkins, W. W., Mize, C. W., & Thompson, M. L. (1995). Design and placement of a multi-species riparian buffer strip system. Agroforestry systems, 29, 201–226.

[39] De Serio, F., Ben Meftah, M., Mossa, M., & Termini, D. (2018). Experimental investigation on dispersion mechanisms in rigid and flexible vegetated beds. Advances in Water Resources, 120, 98–113.

[40] Shucksmith, J. D., Boxall, J. B., & Guymer, I. (2011). Determining longitudinal dispersion coefficients for submerged vegetated flow. Water Resources Research, 47(10), 1–13.

[41] Sonnenwald, F., Hart, J. R., West, P., Stovin, V. R., & Guymer, I. (2017). Transverse and longitudinal mixing in real emergent vegetation at low velocities. Water Resources Research, 53(1), 961–978.

[42] Stoesser, T., Kim, S. J., & Diplas, P. (2010). Turbulent flow through idealized emergent vegetation. Journal of Hydraulic Engineering, 136(12), 1003–1017.

[43] Tanino, Y., & Nepf, H. M. (2008). Lateral dispersion in random cylinder arrays at high Reynolds number. Journal of Fluid Mechanics, 600, 339–371.

[44] Taylor, G. I. (1953). Dispersion of soluble matter in solvent flowing slowly through a tube. Proceedings of the Royal Society of London, Series A: Mathematical and Physical Sciences, 219(1137), 186–203.

[45] Termini, D. (2016). Reduction of scouring downstream of a rigid bed by means of a vegetated carpet: Experimental investigation in a laboratory flume. Environmental Fluid Mechanics, 16, 1111–1127.

[46] Termini, D. (2019). Turbulent mixing and dispersion mechanisms over flexible and dense vegetation. Acta Geophysica, 67(3), 961–970.

[47] Ting, F. C. K., & Kirby, J. T. (1994). Observation of undertow and turbulence in a laboratory surf zone. Coastal Engineering, 24(1–2), 51–80.

[48] Ting, F. C. K., & Kirby, J. T. (1995). Dynamics of surf-zone turbulence in a strong plunging breaker. Coastal Engineering, 24(3–4), 177–204.

[49] Valentine, E. M., & Wood, I. R. (1977). Longitudinal dispersion with dead zones. Journal of the Hydraulics Division, 103(9), 975–990.

[50] Valyrakis, M., Gilja, G., Liu, D., & Latessa, G. (2024). Transport of floating plastics through the fluvial vector: The impact of riparian zones. Water, 16(8), 1098.

[51] Valyrakis, M., Liu, D., Turker, U., & Yagci, O. (2021). The role of increasing riverbank vegetation density on flow dynamics across an asymmetrical channel. Environmental Fluid Mechanics, 21, 643–666.

[52] Västilä K., Oh, J., Sonnenwald, F., Ji, U., Järvelä J., Bae, I., & Guymer, I. (2022). Longitudinal dispersion affected by willow patches of low areal coverage. Hydrological Processes, 36(6), e14613.

[53] White, B. L., & Nepf, H. M. (2003). Scalar transport in random cylinder arrays at moderate Reynolds number. Journal of Fluid Mechanics, 487, 43–79.

[54] Zhang, J., Wang, W., Li, Z., Wang, H., Wang, Q., & Mi, Z. (2023). Evaluation of a random displacement model for scalar mixing in ecological channels partially covered with vegetation. Environmental Science and Pollution Research, 30(11), 31281–31293.

[55] Zong, L., & Nepf, H. (2012). Vortex development behind a finite porous obstruction in a channel. Journal of Fluid Mechanics, 691, 368–391.

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