Hostname: page-component-cd9895bd7-fscjk Total loading time: 0 Render date: 2025-01-02T15:14:36.722Z Has data issue: false hasContentIssue false
  • English
  • Français

Flow adjustment and interior flow associated with a rectangular porous obstruction

Published online by Cambridge University Press:  13 June 2011

JEFFREY T. ROMINGER  and
HEIDI M. NEPF
JEFFREY T. ROMINGER
Affiliation:
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
HEIDI M. NEPF
Affiliation:
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Get access Rights & Permissions [Opens in a new window]

Abstract

The flow at the leading edge and in the interior of a rectangular porous obstruction is described through experiments and scaling. The porous obstruction consists of an emergent, rectangular array of cylinders in shallow flow, a configuration that mimics aquatic vegetation. The main features of the flow depend upon the non-dimensional canopy flow-blockage, which is a function of the obstruction width and porosity. For the ranges of canopy flow-blockage tested in this paper, the fluid decelerates upstream of the obstruction over a length scale proportional to the array width. For high flow-blockage, the interior adjustment length within the porous obstruction is set by the array width. For low flow-blockage, the array's frontal area per unit volume sets the interior adjustment length. Downstream of the adjustment regions, the interior velocity is governed by a balance between the lateral divergence of the turbulent stress and canopy drag, or by a balance between the pressure gradient and canopy drag, depending on the lateral penetration into the array of Kelvin–Helmholtz (KH) vortices, which is set by the non-dimensional canopy flow-blockage. For a porous obstruction with two stream-parallel edges, the KH vortex streets along the two edges are in communication across the width of the array: a phenomenon that results in cross-array vortex organization, which significantly enhances the vortex strength and creates significant lateral transport within the porous obstruction.

JFM classification

Geophysical and Geological Flows: Coastal engineering Geophysical and Geological Flows: Shallow water flows
Type
Papers
Information
Journal of Fluid Mechanics , Volume 680 , 10 August 2011 , pp. 636 - 659
Copyright
Copyright © Cambridge University Press 2011

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Beavers, G. S. & Joseph, D. D. 1967 Boundary conditions at a naturally permeable wall. J. Fluid Mech. 30, 197–207.CrossRefGoogle Scholar
Belcher, S. E., Finnigan, J. J. & Harman, I. N. 2008 Flows through forest canopies in complex terrain. Ecol. Appl. 18 (6), 1436–1453.CrossRefGoogle ScholarPubMed
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, 369–398.CrossRefGoogle Scholar
Bentham, T. & Britter, R. 2003 Spatially averaged flow within obstacle arrays. Atmos. Environ. 37, 2037–2043.CrossRefGoogle Scholar
Bouma, T. J., van Duren, L. A., Temmerman, S., Claverie, T., Blanco-Garcia, A., Ysebaerty, T. & Herman, P. M. J. 2007 Spatial flow and sedimentation patterns within patches of epibenthic structures: combining field, flume and modelling experiments. Cont. Shelf Res. 27, 1020–1045.CrossRefGoogle Scholar
Brown, G. & Roshko, A. 1974 On density effects and large structure in turbulent mixing layers. J. Fluid Mech. 64, 775–816.CrossRefGoogle Scholar
Coceal, O. & Belcher, S. E. 2004 A canopy model of mean winds through urban areas. Q. J. R. Met. Soc. 130, 1349–1372.CrossRefGoogle Scholar
Drazin, P. & Reid, W. 1981 Hydrodynamic Stability. Cambridge University Press.Google Scholar
Eames, I., Hunt, J. C. R. & Belcher, S. E. 2004 Inviscid mean flow through and around groups of bodies. J. Fluid Mech. 515, 371–389.CrossRefGoogle Scholar
Finnigan, J. J. 2000 Turbulence in plant canopies. Annu. Rev. Fluid Mech. 32, 519–571.CrossRefGoogle Scholar
Finnigan, J. J. & Shaw, R. H. 2000 A wind-tunnel study of airflow in waving wheat: an EOF analysis of the structure of the large-eddy motion. Boundary Layer Meteorol. 96, 211–255.CrossRefGoogle Scholar
Gaylord, B., Rosman, J. H., Reed, D. C., Koseff, J. R., Fram, J., MacIntyre, S., Arkema, K., McDonald, C., Brzezinski, M. A., Largier, J. L., Monismith, S. G., Raimondi, P. T. & Mardian, S. 2007 Spatial patterns of flow and their modification within and around a giant kelp forest. Limnol. Oceanogr. 52 (5), 1838–1852.CrossRefGoogle Scholar
Ghisalberti, M. & Nepf, H. M. 2002 Mixing layers and coherent structures in vegetated aquatic flows. J. Geophys. Res. 107 (C2), 3011.CrossRefGoogle Scholar
Ghisalberti, M. & Nepf, H. M. 2009 Shallow flows over a permeable medium: the hydrodynamics of submerged aquatic canopies. Transport in Porous Media 78, 309–326.CrossRefGoogle Scholar
Gray, W. G. & Lee, P. C. Y. 1977 On the theorems for local volume averaging of multiphase systems. Intl J. Multiphase Flow 3 (4), 333–340.CrossRefGoogle Scholar
Grimmond, C. S. B. & Oke, T. R. 1999 Aerodynamic properties of urban areas derived from analysis of surface form. J. Appl. Meteorol. 38 (9), 1262–1292.2.0.CO;2>CrossRefGoogle Scholar
Ho, C. & Huerre, P. 1984 Perturbed free shear layers. Annu. Rev. Fluid Mech. 16, 365–424.CrossRefGoogle Scholar
Jackson, G. A. 1997 Currents in the high drag environment of a coastal kelp stand off california. Cont. Shelf Res. 17 (15), 1913–1928.CrossRefGoogle Scholar
Jackson, G. A. & Winant, C. D. 1983 Effect of a kelp forest on coastal currents. Cont. Shelf Res. 2 (1), 75–80.CrossRefGoogle Scholar
Koch, D. L. & Ladd, A. J. C. 1997 Moderate Reynolds number flows through periodic and random arrays of aligned cylinders. J. Fluid Mech. 349, 31–66.CrossRefGoogle Scholar
Krzikalla, F. 2005 Numerical investigation of the interaction between wind and forest and heterogeneous conditions. Master's thesis, University of Karlsruhe.Google Scholar
Luhar, M., Coutu, S., Infantes, E., Fox, S. & Nepf, H. 2010 Wave-induced velocities inside a model seagrass bed. J. Geophys. Res. 115, C12005.CrossRefGoogle Scholar
Nepf, H. M., Ghisalberti, M., White, B. L. & Murphy, E. 2007 Retention time and dispersion associated with submerged aquatic canopies. Water Resour. Res. 43, W04422.CrossRefGoogle Scholar
Nikora, V., McEwan, I., McLean, S., Coleman, S., Pokrajac, D. & Walters, R. 2007 Double-averaging concept for rough-bed open-channel and overland flows: theoretical background. J. Hydraul. Engng 133 (8), 873–883.CrossRefGoogle Scholar
Poggi, D., Katul, G. & Albertson, J. 2004 a A note on the contribution of dispersive fluxes to momentum transfer within canopies. Boundary Layer Meteorol. 11 (3), 615–621.CrossRefGoogle Scholar
Poggi, D., Porporato, A., Ridolfi, L., Albertson, J. D. & Katul, G. G. 2004 b The effect of vegetation density on canopy sub-layer turbulence. Boundary Layer Meteorol. 111, 565–587.CrossRefGoogle 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, 351–382.CrossRefGoogle Scholar
Raupach, M. R. & Shaw, R. H. 1982 Averaging procedures for flow within vegetation canopies. Boundary Layer Meteorol. 22, 79–90.CrossRefGoogle Scholar
Rosman, J. H., Koseff, J. R., Monismith, S. G. & Grover, J. 2007 A field investigation into the effects of a kelp forest (macrocystis pyrifera) on costal hydrodynamics and transport. J. Geophys. Res. 112, C02016.CrossRefGoogle Scholar
Sand-Jensen, K. & Pedersen, M. L. 2008 Streamlining of plant patches in streams. Freshwat. Biol. 53, 714–726.CrossRefGoogle Scholar
Schatz, M., Barkley, D. & Swinney, H. 1995 Instability in a spatially periodic open flow. Phys. Fluids 7 (2), 344–358.CrossRefGoogle Scholar
Tamai, N., Asaeda, T. & Ikeda, H. 1986 Study on generation of periodical large surface eddies in a composite channel flow. Water Resour. Res. 22, 1129–1138.CrossRefGoogle 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.CrossRefGoogle Scholar
Thom, A. S. 1971 Momentum absorption by vegetation. Q. J. R. Meteorol. Soc. 96, 414–428.CrossRefGoogle Scholar
Vogel, S. 1994 Life in Moving Fluids: The Physical Biology of Flow, 2nd edn. Princeton University Press.Google Scholar
White, B. L. & Nepf, H. M. 2007 Shear instability and coherent structures in shallow flow adjacent to a porous layer. J. Fluid Mech. 593, 1–32.CrossRefGoogle Scholar
Zong, L. & Nepf, H. 2010 Flow and deposition in and around a finite patch of vegetation. Geomorphology 116, 363–372.CrossRefGoogle Scholar