A two-layer approach for depth-limited open-channel flows with submerged vegetation

A two-layer approach for depth-limited open-channel flow with submerged vegetation is described. A momentum balance is applied to each layer and expressions for the mean velocities are proposed. The velocity is assumed to be uniform in the vegetation layer and logarithmic in the upper layer. The proposed relationship successfully predicts the mean velocity distribution when compared with the measured data. Using the velocity formula, the layer-averaged mean velocities in the upper layer and over the entire layer are derived. An expression for the roughness coefficient increased by vegetation is also presented, performing better for the roughness coefficient than other formulas. Another relationship is proposed for predicting the distribution of suspended sediment in depth-limited flow with submerged vegetation by using an eddy-viscosity profile. The predicted profiles moderately agree with the measured data. Comparisons with simulated data from the Reynolds-averaged Navier–Stokes equations with the k–ϵ model suggest that these proposals successfully predict suspended sediment transport in a depth-limited flow with submerged vegetation.

[1]  Syunsuke Ikeda,et al.  Three-Dimensional Organized Vortices above Flexible Water Plants , 1996 .

[2]  Z. G. Xu,et al.  Three-layer model for vertical velocity distribution in open channel flow with submerged rigid vegetation , 2009 .

[3]  Nicholas Kouwen,et al.  BIOMECHANICS OF VEGETATIVE CHANNEL LININGS , 1980 .

[4]  Marco Ghisalberti,et al.  The limited growth of vegetated shear layers , 2004 .

[5]  Fabian Lopez.  Open-Channel Flow With Roughness Elements of Different Spanwise Aspect Ratios: Turbulence Structure and Numerical Modeling , 1997 .

[6]  H. Nepf,et al.  Mixing layers and coherent structures in vegetated aquatic flows , 2002 .

[7]  Fabián López,et al.  open‐channel flow through simulated vegetation: Suspended sediment transport modeling , 1998 .

[8]  V. Babovic,et al.  On inducing equations for vegetation resistance , 2007 .

[9]  Nicholas Kouwen,et al.  Flow Retardance in Vegetated Channels , 1969 .

[10]  Marc R. Hoffmann.  APPLICATION OF A SIMPLE SPACE-TIME AVERAGED POROUS MEDIA MODEL FOR FLOW IN DENSELY VEGETATED CHANNELS , 2002 .

[11]  Anisotropy of Turbulence in Vegetated Open-Channel Flows , 2005 .

[12]  Darrel M. Temple.  Flow Retardance of Submerged Grass Channel Linings , 1982 .

[13]  Enrique R. Vivoni,et al.  Flow structure in depth-limited, vegetated flow , 2000 .

[14]  Stephen E. Darby,et al.  Effect of Riparian Vegetation on Flow Resistance and Flood Potential , 1999 .

[15]  J. Ackerman.  Diffusivity in a marine macrophyte canopy: implications for submarine pollination and dispersal. , 2002, American journal of botany.

[16]  Luca Ridolfi,et al.  The Effect of Vegetation Density on Canopy Sub-Layer Turbulence , 2004 .

[17]  Aronne Armanini,et al.  Direct measurement of vegetation resistance in prototype scale , 2005 .

[18]  Suzanne J.M.H. Hulscher,et al.  Analytical solution of the depth‐averaged flow velocity in case of submerged rigid cylindrical vegetation , 2007 .

[19]  R. Shaw,et al.  Observation of organized structure in turbulent flow within and above a forest canopy , 1989 .

[20]  John A. Roberson,et al.  A Theory of Flow Resistance for Vegetated Channels , 1976 .

[21]  D. Gutknecht,et al.  Hydraulic resistance of submerged flexible vegetation , 2002 .

[22]  Marco Ghisalberti,et al.  Flow and transport in channels with submerged vegetation , 2008 .

[23]  D. Klopstra,et al.  Analytical model for hydraulic roughness of submerged vegetation , 1997 .

[24]  Nicholas Kouwen,et al.  Field estimation of the biomechanical properties of grass , 1988 .

[25]  Allen Bateman,et al.  A new integrated, hydro-mechanical model applied to flexible vegetation in riverbeds , 2008 .

[26]  Juha Järvelä.  INFLUENCE OF VEGETATION ON FLOW STRUCTURE IN FLOODPLAINS AND WETLANDS , 2003 .

[27]  Sung-Uk Choi,et al.  Reynolds stress modeling of vegetated open-channel flows , 2004 .

[28]  Catherine Wilson,et al.  Flow resistance models for flexible submerged vegetation , 2007 .

[29]  Catherine Wilson,et al.  Open Channel Flow through Different Forms of Submerged Flexible Vegetation , 2003 .

[30]  Sung‐Uk Choi,et al.  Impact of stem flexibility on mean flow and turbulence structure in depth-limited open channel flows with submerged vegetation , 2009 .

[31]  Marco Ghisalberti,et al.  The Structure of the Shear Layer in Flows over Rigid and Flexible Canopies , 2006 .

[32]  Nicholas Kouwen,et al.  FLEXIBLE ROUGHNESS IN OPEN CHANNELS , 1973 .

[33]  Brian M. Stone,et al.  Hydraulic resistance of flow in channels with cylindrical roughness , 2002 .

[34]  T. Tsujimoto,et al.  HYDRAULIC RESISTANCE OF FLOW WITH FLEEXIBLE VEGETATION IN OPEN CHANNEL , 1996 .