Lateral distributions of streamwise velocity in compound channels with partially vegetated floodplains. (English) Zbl 1422.86009
Summary: Natural rivers are commonly characterized by a main channel for primary flow conveyance and a floodplain, often partially covered with vegetation such as shrubs or trees, to carry extra flow during floods. The hydraulic resistance due to vegetation on the floodplain typically causes a further reduction of flow velocity and increases the velocity difference between the main channel and the floodplain. As a consequence a strong lateral shear layer leads to the exchange of mass and momentum between the main channel and floodplain, which in turn affects the overall channel conveyance and certain fluvial processes. The prediction of the lateral velocity distribution is important for many flood alleviation schemes, as well as for studies on sediment transport and dispersion in such channels. The present paper proposes a method for predicting the depth-averaged velocity in compound channels with partially vegetated floodplains, based on an analytical solution to the depth-integrated Reynolds-Averaged Navier-Stokes equation with a term included to account for the effects of vegetation. The vegetation is modelled via an additional term in the momentum equation to account for the additional drag force. The method includes the effects of bed friction, drag force, lateral turbulence and secondary flows, via four coefficients \(f, C_{\text D}, \lambda \& \Gamma \) respectively. The predicted lateral distributions of depth-averaged velocity agree well with the experimental data. The analytical solutions can also be used to predict the distribution of boundary shear stresses, which adds additional weight to the method proposed.
References:
| [1] | Knight D W, Shiono K. Turbulence measurements in a shear layer region of a compound channel. J Hydraul Res, 1990, 28(2): 175–196 · doi:10.1080/00221689009499085 |
| [2] | Knight D W, Shiono K. River channel and floodplain hydraulics. In: Anderson M G, Walling D E, Bates P D, eds. Floodplain Processes. Chichester: Wiley, 1996. 139–181 |
| [3] | Abril J B, Knight D W. Stage-discharge prediction for rivers in flood applying a depth-averaged model. J Hydraul Res, 2004, 42(6): 616–629 · doi:10.1080/00221686.2004.9628315 |
| [4] | Ervine D A, Babaeyan-Koopaei K, Sellin R H J. Two-dimensional solution for straight and meandering overbank flows. J Hydraul Eng, 2000, 126(9): 653–669 · doi:10.1061/(ASCE)0733-9429(2000)126:9(653) |
| [5] | Tominaga A, Nezu I. Turbulent structure in compound open-channel flows. J Hydraul Eng, 1991, 117(1): 21–41 · doi:10.1061/(ASCE)0733-9429(1991)117:1(21) |
| [6] | van Prooijen B C, Battjes J A, Uijttewaal W S J. Momentum exchange in straight uniform compound channel flow. J Hydraul Eng, 2005, 131(3): 175–183 · doi:10.1061/(ASCE)0733-9429(2005)131:3(175) |
| [7] | Tang X, Knight D W. Lateral depth-averaged velocity distribution and bed shear in rectangular compound channels. J Hydraul Eng, 2008, 134(9): 1337–1342 · doi:10.1061/(ASCE)0733-9429(2008)134:9(1337) |
| [8] | Pasche E, Rouve G. Overbank flow with vegetatively roughened flood plains. J Hydraul Eng, 1985, 111(9): 1262–1278 · doi:10.1061/(ASCE)0733-9429(1985)111:9(1262) |
| [9] | Rameshwaran P, Shiono K. Quasi two-dimensional model for straight overbank flows through emergent vegetation on floodplains. J Hydraul Res, 2007, 45(3): 302–315 · doi:10.1080/00221686.2007.9521765 |
| [10] | Fischer-Antze T, Stoesser T, Bates P, et al. 3D numerical modelling of open-channel flow with submerged vegetation. J Hydraul Res, 2001, 39(3): 303–310 · doi:10.1080/00221680109499833 |
| [11] | Tanino Y, Nepf H M. Laboratory investigation of mean drag in a random array of rigid, emergent cylinders. J Hydraul Eng, 2008, 134(1): 34–41 · doi:10.1061/(ASCE)0733-9429(2008)134:1(34) |
| [12] | Shiono K, Knight D W. Turbulent open channel flows with variable depth across the channel. J Fluid Mech, 1991, 222(5): 617–646 · doi:10.1017/S0022112091001246 |
| [13] | Shiono K, Knight D W. Mathematical models of flow in two or multi stage straight channels. In: Proceedings of the International Conference on River Flood Hydraulics. New York: John Wiley & Sons, 1990. 229–238 |
| [14] | Tominaga A, Knight D W. Numerical evaluation of secondary flow effects on lateral momentum transfer in overbank flows. In: Proceedings of the International Conference on Fluvial Hydraulics. London: Taylor & Francis, 2006. 353–361 |
| [15] | Knight D W, Omran M, Abril J B. Boundary conditions between panels in depth-averaged flow models revisited. In: Proceedings of the International Conference on Fluvial Hydraulics. London: Taylor & Francis, 2006. 371–380 |
| [16] | Sun X, Shiono K. Flow resistance of one-line emergent vegetation along the floodplain edge of a compound channel. Adv Water Resour, 2009, 32(3): 430–438 · doi:10.1016/j.advwatres.2008.12.004 |
| [17] | Kravchenko A G, Moin P. Numerical studies of flow over a circular cylinder at ReD = 3900. J Physics Fluid, 2000, 12(2): 403–417 · Zbl 1149.76441 · doi:10.1063/1.870318 |
| [18] | Ghisalberti M, Nepf H M. The limited growth of vegetated shear layers. Water Resour Res, 2004, 40, W07502, doi:10.1029/2003WR 002776 · doi:10.1029/2003WR002776 |
| [19] | Yang K, Cao S, Knight D W. Flow patterns in compound channels with vegetated floodplains. J Hydraul Eng, 2007, 133(2): 148–159 · doi:10.1061/(ASCE)0733-9429(2007)133:2(148) |
This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. In some cases that data have been complemented/enhanced by data from zbMATH Open. This attempts to reflect the references listed in the original paper as accurately as possible without claiming completeness or a perfect matching.
