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On the surface expression of a canopy-generated shear instability

Published online by Cambridge University Press:  26 March 2019

Tracy L. Mandel Open the ORCID record for Tracy L. Mandel [Opens in a new window] ,
Saksham Gakhar ,
Hayoon Chung ,
Itay Rosenzweig Open the ORCID record for Itay Rosenzweig [Opens in a new window]  and
Jeffrey R. Koseff Open the ORCID record for Jeffrey R. Koseff [Opens in a new window]
Tracy L. Mandel*
Affiliation:
Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA School of Natural Sciences, University of California, Merced, CA 95343, USA
Saksham Gakhar
Affiliation:
Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA
Hayoon Chung
Affiliation:
Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA
Itay Rosenzweig
Affiliation:
Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA
Jeffrey R. Koseff
Affiliation:
Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA
*
†Email address for correspondence: tmandel2@ucmerced.edu
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Abstract

Results are presented from a laboratory study on the free-surface signal generated over an array of submerged circular cylinders, representative of submerged aquatic vegetation. We aim to understand whether aquatic ecosystems generate a surface signature that is indicative of both what is beneath the water surface as well as how it is altering the flow. A shear layer forms over the canopy, generating coherent vortex structures which eventually manifest in the free-surface slope field. We connect the vortex properties measured at the surface with measurements of the bulk flow, and show that correlations between these quantities are adequate to create a parameterized model in which the interior velocity profile can be predicted solely from measurements taken at the free surface. Experimental surface observations yield a Strouhal number that is twice the most amplified mode predicted by linear stability theory, suggesting that vortices may evolve between generation at the canopy height and their manifestation at the water surface. Additionally, the surface signal continues evolving with distance downstream, with vortices becoming spread farther apart and the passage frequency gradually decreasing. By the trailing edge of the canopy, surface-impacting boils emerge for canopies with higher submergence ratios, suggesting a transition from coherent two-dimensional rollers to transversely varying structures.

JFM classification

Waves/Free-surface Flows: Channel flow Geophysical and Geological Flows: Shallow water flows Wakes/Jets: Shear layers
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 867 , 25 May 2019 , pp. 633 - 660
Copyright
© 2019 Cambridge University Press 

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References

Bailey, B. N. & Stoll, R. 2016 The creation and evolution of coherent structures in plant canopy flows and their role in turbulent transport. J. Fluid Mech. 789, 425–460.Google Scholar
Batchelor, G. 1967 An Introduction to Fluid Dynamics. Cambridge University Press.Google Scholar
Biancofiore, L., Heifetz, E., Hoepffner, J. & Gallaire, F. 2017 Understanding the destabilizing role for surface tension in planar shear flows in terms of wave interaction. Phys. Rev. Fluids 2 (10), 103901.Google Scholar
Chen, Z., Jiang, C. & Nepf, H. M. 2013 Flow adjustment at the leading edge of a submerged aquatic canopy. Water Resour. Res. 49, 5337–5551.Google Scholar
Chickadel, C. C., Horner-Devine, A. R., Talke, S. A. & Jessup, A. T. 2009 Vertical boil propagation from a submerged estuarine sill. Geophys. Res. Lett. 36 (10), L10601.Google Scholar
Coceal, O. & Belcher, S. 2004 A canopy model of mean winds through urban areas. Q. J. R. Meteorol. Soc. 130 (599), 1349–1372.Google Scholar
Cornelisen, C. D. & Thomas, F. I. M. 2004 Ammonium and nitrate uptake by leaves of the seagrass Thalassia testudinum: Impact of hydrodynamic regime and epiphyte cover on uptake rates. J. Mar. Syst. 49 (1), 177–194.Google Scholar
Cornelisen, C. D. & Thomas, F. I. M. 2006 Water flow enhances ammonium and nitrate uptake in a seagrass community. Mar. Ecol. 312, 1–13.Google Scholar
Davies, A. G. & Heathershaw, A. D. 1984 Surface-wave propagation over sinusoidally varying topography. J. Fluid Mech. 144, 419–443.Google Scholar
Finnigan, J. 2000 Turbulence in plant canopies. Annu. Rev. Fluid Mech. 32 (1), 519–571.Google Scholar
Finnigan, J. J. 1979 Turbulence in waving wheat. I. Mean statistics and honami. Boundary-Layer Meteorol. 16 (3), 181–211.Google Scholar
Finnigan, J. J., Shaw, R. H. & Patton, E. G. 2009 Turbulence structure above a vegetation canopy. J. Fluid Mech. 637, 387–424.Google Scholar
Ghisalberti, M. & Nepf, H. 2006 The structure of the shear layer in flows over rigid and flexible canopies. Environ. Fluid Mech. 6 (3), 277–301.Google Scholar
Ghisalberti, M. & Nepf, H. 2009 Shallow flows over a permeable medium: the hydrodynamics of submerged aquatic canopies. Trans. Porous Med. 78 (2), 309–326.Google Scholar
Ghisalberti, M. & Nepf, H. M. 2002 Mixing layers and coherent structures in vegetated aquatic flows. J. Geophys. Res. 107 (C2), 3011.Google Scholar
Ghisalberti, M. & Nepf, H. M. 2004 The limited growth of vegetated shear layers. Water Resour. Res. 40 (7), W07502.Google Scholar
Ho, C.-M. & Huerre, P. 1984 Perturbed free shear layers. Annu. Rev. Fluid Mech. 16, 365–424.Google Scholar
Järvelä, J. 2002 Flow resistance of flexible and stiff vegetation: A flume study with natural plants. J. Hydrol. 269 (1), 44–54.Google Scholar
Lowe, R. J., Koseff, J. R. & Monismith, S. G. 2005 Oscillatory flow through submerged canopies: 1. Velocity structure. J. Geophys. Res. 110 (C10), C10016.Google Scholar
Luhar, M., Rominger, J. & Nepf, H. 2008 Interaction between flow, transport and vegetation spatial structure. Environ. Fluid Mech. 8 (5–6), 423–439.Google Scholar
Mandel, T. L., Rosenzweig, I., Chung, H., Ouellette, N. T. & Koseff, J. R. 2017 Characterizing free-surface expressions of flow instabilities by tracking submerged features. Exp. Fluids 58 (11), 153.Google Scholar
Moisy, F., Rabaud, M. & Salsac, K. 2009 A synthetic Schlieren method for the measurement of the topography of a liquid interface. Exp. Fluids 46 (6), 1021–1036.Google Scholar
Narayanan, C., Rama Rao, V. & Kaihatu, J. 2004 Model parameterization and experimental design issues in nearshore bathymetry inversion. J. Geophys. Res. 109 (C8), C08006.Google Scholar
Nepf, H., Rominger, J. & Zong, L. 2013 Coherent flow structures in vegetated channels. In Coherent Flow Structures at Earth’s Surface (ed. Venditti, J. G., Best, J. L., Church, M. & Hardy, R. J.), pp. 135–147. Wiley.Google Scholar
Nepf, H. M. 2011 Flow over and through biota. In Treatise on Estuarine and Coastal Science, pp. 267–288. Elsevier.Google Scholar
Nepf, H. M. & Vivoni, E. R. 2000 Flow structure in depth-limited, vegetated flow. J. Geophys. Res. 105 (C12), 28547–28557.Google Scholar
Nezu, I. & Sanjou, M. 2008 Turbulence structure and coherent motion in vegetated canopy open-channel flows. J. Hydro-Environ. Res. 2 (2), 62–90.Google Scholar
Nikora, V., Larned, S., Nikora, N. & Debnath, K. 2008 Hydraulic resistance due to aquatic vegetation in small streams: field study. J. Hydraul. Engng 134 (9), 1326–1332.Google Scholar
Okamoto, T.-A. & Nezu, I. 2009 Turbulence structure and ‘Monami’ phenomena in flexible vegetated open-channel flows. J. Hydraul. Res. 47 (6), 798–810.Google Scholar
Okamoto, T.-A., Nezu, I. & Sanjou, M. 2016 Flow–vegetation interactions: length-scale of the ‘monami’ phenomenon. J. Hydraul. Res. 54 (3), 251–262.Google Scholar
O’Riordan, C., Monismith, S. G. & Koseff, J. R. 1993 A study of concentration boundary-layer formation over a bed of model bivalves. Limnol. Oceanogr. 38 (8), 1712–1739.Google Scholar
Orth, R. J., Luckenbach, M. & Moore, K. A. 1994 Seed dispersal in a marine macrophyte: implications for colonization and restoration. Ecology 75 (7), 1927–1939.Google Scholar
Ouellette, N. T., Xu, H. & Bodenschatz, E. 2006 A quantitative study of three-dimensional Lagrangian particle tracking algorithms. Exp. Fluids 40 (2), 301–313.Google Scholar
Poggi, D., Katul, G. G. & Albertson, J. D. 2004 A note on the contribution of dispersive fluxes to momentum transfer within canopies. Boundary-Layer Meteorol. 111 (3), 615–621.Google Scholar
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), 351–382.Google Scholar
Rosenzweig, I.2017 Experimental investigation of the surface expression of a canopy-induced shear instability. PhD thesis, Stanford University, Stanford, CA.Google Scholar
Sanjou, M., Nezu, I. & Okamoto, T. 2017 Surface velocity divergence model of air/water interfacial gas transfer in open-channel flows. Phys. Fluids 29 (4), 045107.Google Scholar
Savelsberg, R. & van de Water, W. 2008 Turbulence of a free surface. Phys. Rev. Lett. 100 (3), 034501.Google Scholar
Stegner, A. & Wesfreid, J. E. 1999 Dynamical evolution of sand ripples under water. Phys. Rev. E 60 (4), R3487–R3490.Google Scholar
Tanino, Y. & Nepf, H. M. 2008 Laboratory investigation of mean drag in a random array of rigid, emergent cylinders. J. Hydraul. Engng 134 (1), 34–41.Google Scholar
Tsai, W.-T. 1998 A numerical study of the evolution and structure of a turbulent shear layer under a free surface. J. Fluid Mech. 354, 239–276.Google Scholar
Weideman, J. A. & Reddy, S. C. 2000 A MATLAB differentiation matrix suite. ACM Trans. Math. Softw. 26 (4), 465–519.Google Scholar