Velocity Profiles in Vegetated Open-Channel Flows: Combined Effects of Multiple Mechanisms
This article has been corrected.
VIEW CORRECTIONPublication: Journal of Hydraulic Engineering
Volume 139, Issue 10
Abstract
Vertical profile of longitudinal velocity in vegetated channels reflects complex mechanics of flow-vegetation interactions and determines the bulk flow velocity and flow rate. Most available models of velocity profiles in vegetated channels are based on a single physical concept that underpins theoretical considerations and data interpretation. However, measured velocity profiles suggest that the use of a single concept is not sufficient to cover all possible scenarios of flow-vegetation interactions. As a result, a number of models in which different concepts are applied to different flow regions have been recently developed. Within this framework, the overall velocity profile is represented with a set of linked segments. Although such segment-based models have improved velocity profile description, there is a need for more robust approaches and better analytical formulations. This paper proposes a new approach where a vertical velocity profile in vegetated channels is modelled as a linear superposition of four concepts: (1) uniform velocity distribution, (2) mixing layer analogy and a hyperbolic tangent profile, (3) boundary layer concept and a logarithmic profile, and (4) wake function concept. In contrast to the segment-based models, the proposed analytical expression combines these concepts simultaneously over the whole flow depth allowing significant overlaps of the momentum transport and turbulence production mechanisms. The model is tested using extensive laboratory experiments.
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Acknowledgments
The research was partly supported by the Leverhulme Trust, grant F/00152/Z “Biophysics of flow-plant interactions in aquatic systems,” FP7-People-2012-ITN grant HYTECH, GA-2012-316546, and also stimulated by the Scientific Research Network WO.027p11N.
References
Carollo, F. G., Ferro, V., and Termini, D. (2002). “Flow velocity measurements in vegetated channels.” J. Hydraul. Eng., 128(7), 664–673.
Coleman, N. L. (1986). “Effects of suspended sediment on the open-channel velocity distribution.” Water Resour. Res., 22(10), 1377–1384.
Coles, D. (1956). “The law of the wake in the turbulent boundary layer.” J. Fluid Mech., 1(2), 191–226.
Folkard, A. M. (2011). “Vegetated flows in their environmental context: A review.” Proc. Inst. Civ. Eng. Eng. Comput. Mech., 164(1), 3–24.
Ghisalberti, M., and Nepf, H. M. (2002). “Mixing layers and coherent structures in vegetated aquatic flows.” J. Geophys. Res., 107(C2), 3-1–3-11.
Ghisalberti, M., and Nepf, H. M. (2004). “The limited growth of vegetated shear layers.” Water Resour. Res., 40(7), W07502.
Inoue, E. (1963). “On the turbulent structure of air-flow within crop canopies.” J. Meteor. Soc. Japan, 41(6), 317–326.
Järvelä, J. (2002). “Flow resistance of flexible and stiff vegetation: a flume study with natural plants.” J. Hydrol., 269(1–2), 44–54.
Katul, G., Poggi, D., and Ridolfi, L. (2011). “A flow resistance model for assessing the impact of vegetation on flood routing mechanics.” Water Resour. Res., 47(8), W08533.
Katul, G., Wiberg, P., Albertson, J., and Hornberger, G. (2002). “A mixing layer theory for flow resistance in shallow streams.” Water Resour. Res., 38(11), 32-1–32-8.
Kironoto, B. A., and Graf, W. H. (1994). “Turbulence characteristics in rough uniform open-channel flow.” Proc. Inst. Civ. Eng. Water Marit. Energy, 106(4), 333–344.
Kironoto, B. A., and Graf, W. H. (1995). “Turbulence characteristics in rough non-uniform open-channel flow.” Proc. Inst. Civ. Eng. Water Marit. Energy, 112(4), 336–348.
Kouwen, N., and Li, R. M. (1980). “Biomechanics of vegetative channel linings.” J. Hydraul. Div., ASCE, 106(HY6), 1085–1103.
Kouwen, N., Unny, T. E., and Hill, H. M. (1969). “Flow retardance in vegetated channels.” J. Hydraul. Div., ASCE, 95(IR2), 329–342.
Maltese, A., Cox, E., Folkard, A. M., Ciraolo, G., La Loggia, G., and Lombardo, G. (2007). “Laboratory measurements of flow and turbulence in discontinuous distributions of Ligulate seagrass.” J. Hydraul. Eng., 133(7), 750–760.
Michalke, A. (1964). “On the inviscid instability of the hyperbolic-tangent velocity profile.” J. Fluid Mech., 19(4), 543–556.
Monin, A. S., and Yaglom, A. M. (1971). Statistical fluid mechanics: Mechanics of turbulence, Vol. 1, MIT Press, Boston.
Nepf, H. M. (2012). “Hydrodynamics of vegetated channels.” J. Hydraul. Res., 50(3), 262–279.
Nepf, H. M., and Ghisalberti, M. (2008). “Flow and transport in channels with submerged vegetation.” Acta Geophys., 56(3), 753–777.
Nepf, H. M., and Vivoni, E. R. (2000). “Flow structure in depth-limited, vegetated flow.” J. Geophys. Res., 105(C12), 28,547–28,557.
Nezu, I., and Nakagawa, H. (1993). Turbulence in open-channel flows, IAHR-Monograph, Rotterdam, Netherlands.
Nezu, I., and Rodi, W. (1986). “Open-channel flow measurements with a laser Doppler anemometer.” J. Hydraul. Eng., 112(5), 335–355.
Nezu, I., and Sanjou, M. (2008). “Turbulence structure and coherent motion in vegetated canopy open-channel flows.” J. Hydro-Environ. Res., 2(2), 62–90.
Nikora, V. (2010). “Hydrodynamics of aquatic ecosystems: an interface between ecology, biomechanics and environmental fluid mechanics.” River Res. Appl., 26(4), 367–384.
Nikora, V., Goring, D., McEwan, I., and Griffiths, G. (2001). “Spatially averaged open-channel flow over rough bed.” J. Hydraul. Eng., 127(2), 123–133.
Nikora, V., Koll, K., McEwan, I., McLean, S., and Dittrich, A. (2004). “Velocity distribution in the roughness layer of rough-bed flows.” J. Hydraul. Eng., 130(10), 1036–1042.
Nikora, V., Larned, S., Nikora, N., Debnath, K., Cooper, G., and Reid, M. (2008). “Hydraulic resistance due to aquatic vegetation in small streams: A field study.” J. Hydraul. Eng., 134(9), 1326–1332.
Nikora, V., McEwan, I., McLean, S., Coleman, S., Pokrajac, D., and Walters, R. (2007a). “Double averaging concept for rough-bed open-channel and overland flows: Theoretical background.” J. Hydraul. Eng., 133(8), 873–883.
Nikora, V., et al. (2007b). “Double averaging concept for rough-bed open-channel and overland flows: Applications.” J. Hydraul. Eng., 133(8), 884–895.
Poggi, D., Krug, C., and Katul, G. G. (2009). “Hydraulic resistance of submerged rigid vegetation derived from first-order closure models.” Water Resour. Res., 45(10), W10442.
Poggi, D., Porporato, A., Ridolfi, L., Albertson, J. D., and Katul, G. G. (2004). “The effect of vegetation density on canopy sub-layer turbulence.” Bound.-Lay. Meteorol., 111(3), 565–587.
Pokrajac, D., Finnigan, J. J., Manees, C., McEwan, I., and Nikora, V. (2006). “On the definition of the shear velocity in rough bed open channel flows.” Proc., Int. Conf. on Fluvial Hydraulics River Flow 2006, Vol. 1, Taylor & Francis, London, 89–98.
Raupach, M. R., Finnigan, J. J., and Brunet, Y. (1996). “Coherent eddies and turbulence in vegetation canopies: The mixing layer analogy.” Bound.-Lay. Meteorol., 78(3–4), 351–382.
Righetti, M. (2008). “Flow analysis in a channel with flexible vegetation using double-averaging method.” Acta Geophys., 56(3), 801–823.
Stephan, U., and Gutknecht, D. (2002). “Hydraulic resistance of submerged flexible vegetation.” J. Hydrol., 269(1–2), 27–43.
Wu, F.-C., Shen, H. W., and Chou, Y.-J. (1999). “Variation of roughness coefficients for unsubmerged and submerged vegetation.” J. Hydraul. Eng., 125(9), 934–942.
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Published In
Journal of Hydraulic Engineering
Volume 139 • Issue 10 • October 2013
Pages: 1021 - 1032
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Nov 22, 2012
Accepted: May 21, 2013
Published online: May 23, 2013
Published in print: Oct 1, 2013
Discussion open until: Oct 23, 2013
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