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Impact of height heterogeneity on canopy turbulence

  • A. M. Hamed (a1), M. J. Sadowski (a1), H. M. Nepf (a2) and L. P. Chamorro (a1) (a3) (a4)
Abstract

The flow development above and within homogeneous and heterogeneous canopies was experimentally studied using particle image velocimetry in a refractive-index-matching channel. The experiments were designed to gain insight into the effect of height heterogeneity on the structure and spatial distribution of the turbulence. The homogeneous model (base case) is constituted of elements of height $h$ arranged in a staggered configuration; whereas the heterogeneous canopy resembled a row canopy and consisted of elements of two heights $h_{1}=h+(1/3)h$ and $h_{2}=h-(1/3)h$ alternated every two rows. Both canopies had the same density, element geometry and mean height. The flow was studied under three submergences $H/h=2$ , 3 and 4, where $H$ denotes the flow depth. The experiments were performed at Reynolds number $Re_{H}\simeq 6500$ , 11 300 and 12 300 and nearly constant Froude number $Fr\simeq 0.1$ . Turbulence statistics complemented with quadrant analysis and proper orthogonal decomposition reveal richer flow dynamics induced by height heterogeneity. Topography-induced spatially periodic mean flows are observed for the heterogeneous canopy. Furthermore, and in contrast to the homogeneous case, non-vanishing vertical velocity is maintained across the entire length of the heterogeneous canopy with increased levels at lower submergence depths. Further alternations were induced in the magnitude and distribution of the turbulent kinetic energy, Reynolds shear stress and characteristics of the canopy mixing layer, evidencing enhanced mixing and turbulent transport for the heterogeneous canopy especially at lower submergence depths. Overall, the results indicate that heterogeneous canopies exhibit greater vertical turbulent exchange at the canopy interface, suggesting a potential for greater scalar exchange and a greater impact on channel hydraulic resistance than a homogeneous canopy of similar roughness density.

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Corresponding author
Email address for correspondence: lpchamo@illinois.edu
References
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Bai K. & Katz J. 2014 On the refractive index of sodium iodide solutions for index matching in PIV. Exp. Fluids 55, 16.
Bai K., Katz J. & Meneveau C. 2015 Turbulent flow structures inside a canopy with complex multi-scale elements. Boundary-Layer Meteorol. 155 (3), 435457.
Belcher E. S. 2005 Mixing and transport in urban areas. Phil. Trans. R. Soc. Lond. A 363, 29472968.
Belcher S. E., Harman I. N. & Finnigan J. J. 2011 The wind in the willows: flows in forest canopies in complex terrain. Annu. Rev. Fluid Mech. 44, 479504.
Belcher S. E., Jerram N. & Hunt J. C. R. 2003 Adjustment of a turbulent boundary layer to a canopy of roughness elements. J. Fluid Mech. 488, 369398.
Berkooz G., Holmes P. & Lumley J. L. 1993 The proper orthogonal decomposition in the analysis of turbulent flows. Annu. Rev. Fluid Mech. 25 (1), 539575.
Blois G., Christensen K. T., Best J. L., Elliot G., Austin J., Dutton C., Bragg M., Garcia M. & Fouke B.2012 A versatile refractive-index-matched flow facility for studies of complex flow systems across scientific disciplines. AIAA Paper 2012-0736.
Chahine A., Dupont S., Sinfort C. & Brunet Y. 2014 Wind-flow dynamics over a vineyard. Boundary-Layer Meteorol. 151 (3), 557577.
Chen Z., Jiang C. & Nepf H. M. 2013 Flow adjustments at the leading edge of a submerged quatic canopy. Water Resour. Res. 49, 55375551.
Coceal O. & Belcher S. E. 2004 A canopy model of mean winds through urban areas. Q. J. R. Meteorol. Soc. 130, 13491372.
Dennison W. C., Orth R. J., Moore K. A., Stevenson J. C., Carter V., Kollar S., Bergstorm P. W. & Batiuk R. A. 1993 Assessing water quality with submersed aquatic vegetation. BioScience 43 (2), 8694.
Denny M. W., Gaylord B. P. & Cowen E. A 1997 Flow and flexibility ii. the roles of size and shape in determining wave forces on the bull kelp Nereocystis luetkeana . J. Expl Biol. 200, 31653183.
Dijkstra J. T. & Uittenbogaard R. E. 2010 Modeling the interaction between flow and highly flexible aquatic vegetation. Water Resour. Res. 46 (12), W12547.
Finnigan J. 2000 Turbulence in plant canopies. Annu. Rev. Fluid Mech. 32 (1), 519571.
Fonseca M. S. & Cahalan J. A. 1992 A preliminary evaluation of wave attenuation by four species of seagrass. Estuar. Coast. Shelf Sci. 35, 565576.
Ghisalberti M. 2009 Obstructed shear flows: similarities across systems and scales. J. Fluid Mech. 641, 5161.
Hamed A. M., Kamdar A., Castillo L. & Chamorro L. P. 2015 Turbulent boundary layer over 2D and 3D large scale wavy walls. Phys. Fluids 27, 106601.
Hawkins C. P., Murphy M. L., Anderson N. H. & Wilzbach M. A. 1983 Density of fish and salamanders in relation to riparian canopy and physical habitat in streams of the northwestern United States. Can. J. Fish. Aquat. Sci. 40.
Heilman J. L., McInnes K. J., Savage M. J., Gesch R. W. & Lascano R. J. 1994 Soil and canopy energy balances in a west Texas vineyard. Agric. Forest Meteorol. 71 (1–2), 99114.
Lai C., Katul G., Oren R., Ellsworth D. & Schäfer K. 2000 Modeling CO2 and water vapor turbulent flux distributions within a forest canopy. J. Geophys. Res. Atmos. 105 (D21), 2633326351.
Lu S. S. & Willmarth W. W. 1973 Measurements of the structure of the Reynolds stress in a turbulent boundary layer. J. Fluid Mech. 60 (03), 481511.
Luhar M. & Nepf H. M. 2011 Flow-induced reconfiguration of buoyant and flexible aquatic vegetation. Limnol. Oceanogr. 56 (6), 20032017.
Luhar M. & Nepf H. M. 2013 From the blade scale to the reach scale: a characterization of aquatic vegetative drag. Adv. Water Resour. 51, 305316.
Lumley J. 1970 Stochastic Tools in Turbulence. Academic Press.
Morse A. P., Gardiner B. A. & Marshall B. J. 2002 Mechanisms controlling turbulence development across a forest edge. Boundary-Layer Meteorol. 103 (2), 227251.
Nepf H. M. 2012 Flow and transport in regions with aquatic vegetation. Annu. Rev. Fluid Mech. 44, 123142.
Nepf H. M. & Vivoni E. R. 2000 Flow structure in depth-limited, vegetated flow. J. Geophys. Res. Oceans 105 (C12), 2854728557.
Nezu I. & Sanjou M. 2008 Turbulent structure and coherent motion in vegetated canopy open-channel flows. J. Hydro Environ. Res. 2, 6290.
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 Meteorol. 111 (3), 565587.
Raupach M. R., Finnigan J. J. & Brunet Y. 1996 Coherent eddies and turbulence in vegetation canopies: the mixing-layer analogy. Boundary-Layer Meteorol. 78 (3–4), 351382.
Raupach M. R. & Thom A. S. 1981 Turbulence in and above plant canopies. Annu. Rev. Fluid Mech. 13 (1), 97129.
Rominger J. T. & Nepf H. M. 2011 Flow adjustment and interior flow associated with a rectangule porous obstruction. J. Fluid Mech. 680, 636659.
Sen M., Bhaganagar K. & Juttijudata V. 2007 Application of proper orthogonal decomposition (POD) to investigate a turbulent boundary layer in a channel with rough walls. J. Turbul. 8, N41.
Sirovich L. 1987 Turbulence and the dynamics of coherent structures. Part I: coherent structures. Q. Appl. Maths 45 (3), 561571.
Souch C. & Grimmond S. 2006 Applied climatology: urban climate. Prog. Phys. Geog. 30 (2), 270.
Tanino Y. & Nepf H. M. 2008 Laboratory investigation of mean drag in a random array of rigid, emergent cylinders. J. Hydraul. Engng ASCE 134, 3441.
Weiss A. & Allen L. H. 1976 Air-flow patterns in vineyard rows. Agric. Meteorol. 16 (3), 329342.
White B. L. & Nepf H. M. 2007 Shear instability and coherent structures in shallow flow adjacent to a porous layer. J. Fluid Mech. 593, 132.
Zhu W., van Hout R. & Katz J. 2007 On the flow structure and turbulence during sweep and ejection events in a wind-tunnel model canopy. Boundary-Layer Meteorol. 124 (2), 205233.
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Journal of Fluid Mechanics
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  • EISSN: 1469-7645
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