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Turbulence structure above a vegetation canopy

Published online by Cambridge University Press:  07 October 2009

JOHN J. FINNIGAN ,
ROGER H. SHAW  and
EDWARD G. PATTON
JOHN J. FINNIGAN*
Affiliation:
CSIRO Marine and Atmospheric Research, GPO Box 3023, Canberra, ACT 2601, Australia
ROGER H. SHAW
Affiliation:
University of California, Davis, CA 95616, USA
EDWARD G. PATTON
Affiliation:
National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307-3000, USA
*
†Email address for correspondence: [email protected]
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Abstract

We compare the turbulence statistics of the canopy/roughness sublayer (RSL) and the inertial sublayer (ISL) above. In the RSL the turbulence is more coherent and more efficient at transporting momentum and scalars and in most ways resembles a turbulent mixing layer rather than a boundary layer. To understand these differences we analyse a large-eddy simulation of the flow above and within a vegetation canopy. The three-dimensional velocity and scalar structure of a characteristic eddy is educed by compositing, using local maxima of static pressure at the canopy top as a trigger. The characteristic eddy consists of an upstream head-down sweep-generating hairpin vortex superimposed on a downstream head-up ejection-generating hairpin. The conjunction of the sweep and ejection produces the pressure maximum between the hairpins, and this is also the location of a coherent scalar microfront. This eddy structure matches that observed in simulations of homogeneous-shear flows and channel flows by several workers and also fits with earlier field and wind-tunnel measurements in canopy flows. It is significantly different from the eddy structure educed over smooth walls by conditional sampling based only on ejections as a trigger. The characteristic eddy was also reconstructed by empirical orthogonal function (EOF) analysis, when only the dominant, sweep-generating head-down hairpin was recovered, prompting a re-evaluation of earlier results based on EOF analysis of wind-tunnel data. A phenomenological model is proposed to explain both the structure of the characteristic eddy and the key differences between turbulence in the canopy/RSL and the ISL above. This model suggests a new scaling length that can be used to collapse turbulence moments over vegetation canopies.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 637 , 25 October 2009 , pp. 387 - 424
Copyright
Copyright © Cambridge University Press 2009

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References

REFERENCES

Adrian, R. J. 2007 Hairpin vortex organization in wall turbulence. Phys. Fluids 19, 041301-1–041301-16.CrossRefGoogle Scholar
Adrian, R. J., Meinhart, C. D. & Tomkins, C. D. 2000 Vortex organization in the outer region of the turbulent boundary layer. J. Fluid Mech. 422, 1–54.Google Scholar
Baldocchi, D. D., Falge, E., Gu, L., Olson, R., Hollinger, D., Running, S., Anthoni, P., Bernhofer, C., Davis, K., Evans, R., Fuentes, J., Goldstein, A., Katul, G., Law, B., Lee, X., Malhi, Y., Meyers, T., Munger, W., Oechal, W., Paw, U. K. T., Pilegaard, K., Schmid, H. P., Valentini, R., Verma, S., Vesala, T., Wilson, K. & Wofsy, S. 2001 FLUXNET: a new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapour and energy flux densities. Bull. Am. Meteorol. Soc. 82, 2415–2434.Google Scholar
Baldocchi, D. D. & Hutchinson, B. A. 1987 Turbulence in an almond orchard: vertical variation in turbulence statistics. Boundary-Layer Meteorol. 40, 177–146.CrossRefGoogle Scholar
Bohm, M., Finnigan, J. J. & Raupach, M. R. 2000 Dispersive fluxes and canopy flows: just how important are they? In Proceedings of 24th Conference on Agricultural and Forest Meteorology, American Meteorological Society, Davis, CA.Google Scholar
Brown, G. L. & Roshko, A. 1974 On density effects and large structure in turbulent mixing layers. J. Fluid Mech. 64, 775–816.Google Scholar
Brown, K. W. & Covey, W. 1966 The energy-budget evaluation of the micro-meteorological transfer process within a corn field. Agric. Meteorol. 3, 73–96.Google Scholar
Brunet, Y., Finnigan, J. J. & Raupach, M. R. 1994 A wind tunnel study of air flow in waving wheat: single-point velocity statistics. Boundary-Layer Meteorol. 70, 95–132.Google Scholar
Butler, K. M. & Farrell, B. F. 1992 Three-dimensional optimal perturbations in viscous shear flow. Phys. Fluids A 8, 1637–1650.CrossRefGoogle Scholar
Cellier, P. & Brunet, Y. 1992 Flux-gradient relationships above tall plant canopies. Agric. Forest Meteorol. 58, 93–117.CrossRefGoogle Scholar
Chakraborty, P., Balachandar, S. & Adrian, R. J. 2005 On the relationships between local vortex identification schemes. J. Fluid Mech. 535, 189–214.CrossRefGoogle Scholar
Chen, F. & Schwerdtfeger, P. 1989 Flux-gradient relationships above tall plant canopies. Quart. J. R. Meteorol. Soc. 115, 335–352.Google Scholar
Christen, A. & Vogt, R. 2004 Direct measurement of dispersive fluxes within a cork oak plantation. In Proceedings of 26th Conference on Agricultural and Forest Meteorology, American Meteorological Society, Vancouver, BC, Canada.Google Scholar
Christensen, K. T. & Adrian, R. J. 2001 Statistical evidence of hairpin vortex packets in wall turbulence. J. Fluid Mech. 431, 433–443.Google Scholar
Coceal, O., Dobre, A., Thomas, T. G. & Belcher, S. E. 2007 Structure of turbulent flow over regular arrays of cubical roughness. J. Fluid Mech. 589, 375–409.Google Scholar
Collineau, S. & Brunet, Y. 1993 a Detection of turbulent coherent motions in a forest canopy. Part 1. Wavelet analysis. Boundary-Layer Meteorol. 65, 357–379.CrossRefGoogle Scholar
Collineau, S. & Brunet, Y. 1993 b Detection of turbulent coherent motions in a forest canopy. Part 2. Timescales and conditional averages. Boundary-Layer Meteorol. 66, 49–73.Google Scholar
Deardorff, J. W. 1980 Stratocumulus-capped mixed layers derived from a three-dimensional model. Boundary-Layer Meteorol. 18, 495–527.CrossRefGoogle Scholar
Drazin, P. G. & Reid, W. H. 1981 Hydrodynamic Stability. Cambridge University Press.Google Scholar
Dwyer, M. J., Patton, E. G. & Shaw, R. H. 1997 Turbulent kinetic energy budgets from a large-eddy simulation of airflow above and within a forest. Boundary-Layer Meteorol. 84, 23–43.Google Scholar
Finnigan, J. J. 1979 Turbulence in waving wheat. Part 2. Structure of momentum transfer. Boundary-Layer Meteorol. 16, 213–236.Google Scholar
Finnigan, J. J. 1985 Turbulent transport in flexible plant canopies. In The Forest–Atmosphere Interaction (ed. Hutchison, B. A. & Hicks, B. B.), pp. 443–480. Reidel.Google 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 empirical orthogonal function analysis of the large-eddy motion. Boundary-Layer Meteorol. 96, 211–255.Google Scholar
Finnigan, J. J. & Shaw, R. H. 2008 Double-averaging methodology and its application to turbulent flow in and above vegetation canopies. Acta Geophys. 5, 534–561.CrossRefGoogle Scholar
Fitzmaurice, L., Shaw, R. H., Paw, U. K. T. & Patton, E. G. 2004 Three-dimensional scalar microfront systems in a large-eddy simulation of vegetation canopy flow. Boundary-Layer Meteorol. 112, 107–127.CrossRefGoogle Scholar
Frederiksen, J. S. & Branstator, G. 2005 seasonal variability of teleconnection patterns. J. Atmos. Sci. 62, 1346–1365.Google Scholar
Gao, W., Shaw, R. H. & Paw, U. K. T. 1989 Observation of organized structure in turbulent flow within and above a forest canopy. Boundary-Layer Meteorol. 47, 349–377.CrossRefGoogle Scholar
Gardiner, B. A. 1994 Wind and wind forces in a plantation spruce forest. Boundary-Layer Meteorol. 67, 161–186.CrossRefGoogle Scholar
Garratt, J. R. 1980 Surface influence on vertical profiles in the atmospheric near-surface layer. Quart. J. R. Meteorol. Soc. 106, 803–819.Google Scholar
Garratt, J. R. 1983 Surface influence upon vertical profiles in the nocturnal boundary layer. Boundary-Layer Meteorol. 26, 69–80.CrossRefGoogle Scholar
Gerz, T., Howell, J. & Mahrt, L. 1994 Vortex structures and microfronts. Phys. Fluids 6, 1242–1251.Google Scholar
Ghisalberti, M. & Nepf, H. 2002 Mixing layers and coherent structures in vegetated aquatic flow. J. Geophys. Res. 107, 1–11.Google Scholar
Grass, A. J. 1971 Structural features of turbulent flow over smooth and rough boundaries. J. Fluid Mech. 50, 233–255.Google Scholar
Haidari, A. H. & Smith, C. R. 1994 The generation and regeneration of single hairpin vortices. J. Fluid Mech. 277, 135–162.Google Scholar
Harman, I. N. & Finnigan, J. F. 2007 A simple unified theory for flow in the canopy and roughness sublayer. Boundary-Layer Meteorol. 123, 339–363.CrossRefGoogle Scholar
Harman, I. N. & Finnigan, J. F. 2008 Scalar concentration profiles in the canopy and roughness sublayer. Boundary-Layer Meteorol. 129, 323–351.Google Scholar
Head, M. & Bandyopadhyay, P. 1981 New aspects of turbulent boundary layer structure. J. Fluid Mech. 107, 297–338.Google Scholar
Holmes, P., Lumley, J. L. & Berkooz, G. 1996 Turbulence, Coherent Structures, Dynamical Systems and Symmetry. Cambridge University Press.CrossRefGoogle Scholar
Hunt, J. C. R. & Carruthers, D. J. 1990 rapid distortion theory and the ‘problems’ of turbulence. J. Fluid Mech. 212, 497–532.CrossRefGoogle Scholar
Hunt, J. C. R. & Morrison, J. F. 2000 Eddy structure in turbulent boundary layers. Eur. J. Mech. B. 19, 673–694.Google Scholar
Jeong, J. & Hussain, F. 1995 On the identification of a vortex. J. Fluid Mech. 285, 69–94.Google Scholar
Jeong, J., Hussain, F., Schoppa, W. & Kim, J. 1997 Coherent structures near the wall in a turbulent channel flow. J. Fluid Mech. 332, 185–214.Google Scholar
Kaimal, J. C. & Finnigan, J. J. 1994 Atmospheric Boundary Layer Flows: Their Structure and Measurement. Oxford University Press.CrossRefGoogle Scholar
Katul, G. & Vidakovic, B. 1998 Identification of low-dimensional energy containing/flux transporting eddy motion in the atmospheric surface layer using wavelet thresholding methods. J. Atmos. Sci. 55, 377–389.2.0.CO;2>CrossRefGoogle Scholar
Katul, G. G., Poggi, D., Cava, D. & Finnigan, J. J. 2006 The relative importance of ejections and sweeps to momentum transfer in the atmospheric boundary layer. Boundary-Layer Meteorol. 120, 367–375.CrossRefGoogle Scholar
Kim, J. & Moin, P. 1986 The structure of the vorticity field in turbulent channel flow. Part 2. Study of ensemble-averaged fields. J. Fluid Mech. 162, 339–363.Google Scholar
Leonard, A. 1974 Energy cascade in large-eddy simulations of turbulent fluid flows. Adv. Geophys. 18A, 237–248.Google Scholar
Liu, J. T. C. 1988 Contributions to the understanding of large-scale coherent structures in developing free turbulent shear flows. Adv. Appl. Mech. 26, 183–309.Google Scholar
Liu, Z., Adrian, R. J. & Hanratty, T. J. 2001 Large-scale modes of turbulent channel flow: transport and structure. J. Fluid Mech. 448, 53–80.Google Scholar
Lu, S. S. & Willmarth, W. W. 1973 Measurements of the structure of Reynolds stress in a turbulent boundary layer. J. Fluid Mech. 60, 481–571.Google Scholar
Lumley, J. L. 1967 The structure of inhomogeneous turbulent flows. In Atmospheric Turbulence and Radio Wave Propagation (ed. Yaglom, A. M. & Tatarsky, V. I.), p. 166. Nauka.Google Scholar
McKeon, B. J. & Sreenivasen, K. R. 2007 Introduction: scaling and structure in high Reynolds number wall-bounded flows. Phil. Trans. R. Soc. A 365, 635–646.Google Scholar
Michalke, A. 1964 On the inviscid instability of the hyperbolic-tangent velocity profile. J. Fluid Mech. 19, 543–556.Google Scholar
Michalke, A. 1965 On spatially growing disturbances in an inviscid shear layer. J. Fluid Mech. 23, 521–544.CrossRefGoogle Scholar
Moin, P. & Kim, J. 1985 The structure of the vorticity field in a turbulent channel flow. part 1. analysis of the instantaneous fields and statistical correlations. J. Fluid Mech. 155, 441–464.Google Scholar
Moin, P. & Moser, R. D. 1989 Characteristic-eddy decomposition of turbulence in a channel. J. Fluid Mech. 200, 471–509.CrossRefGoogle Scholar
Mölder, M., Grelle, A., Lindroth, A. & Halldin, S. 1999 Flux-profile relationships over a boreal forest-roughness sublayer corrections. Agric. Forest Meteorol. 98–99, 645–658.Google Scholar
Moser, R. D. & Rogers, M. M. 1993 The three-dimensional evolution of a plane mixing layer: pairing and the transition to turbulence. J. Fluid Mech. 247, 275–320.CrossRefGoogle Scholar
Patton, E. G., Davis, K. J., Barth, M. C. & Sullivan, P. P. 2001 Decaying scalars emitted by a forest canopy – a numerical study. Boundary-Layer Meteorol. 100, 91–129.Google Scholar
Patton, E. G., Sullivan, P. P. & Davis, K. J. 2003 The influence of a forest canopy on top-down and bottom-up diffusion in the planetary boundary layer. Quart. J. R. Meteorol. Soc. 129, 1415–1434.Google Scholar
Patton, E. G., Sullivan, P. P. & Moeng, C.-H. 2005 The influence of idealized heterogeneity on wet and dry planetary boundary layers coupled to the land surface. J. Atmos. Sci. 62, 2078–2097.Google Scholar
Perry, A. E. & Maruic, I. 1995 A wall-wake model for the turbulence structure of boundary layers. Part 1. Extension of the attached eddy hypothesis. J. Fluid Mech. 298, 361–388.Google Scholar
Pierrehumbert, R. T. & Widnall, S. E. 1982 The two- and three-dimensional instabilities of a spatially periodic shear layer. J. Fluid Mech. 112, 467–474.Google Scholar
Raupach, M. R. 1979 Anomalies in flux-gradient relationships over forest. Boundary-Layer Meteorol. 16, 467–486.CrossRefGoogle Scholar
Raupach, M. R. 1992 Drag and drag partition on rough surfaces. Boundary-Layer Meteorol. 60, 375–395.Google Scholar
Raupach, M. R., Coppin, P. A. & Legg, B. J. 1986 Experiments on scalar dispersion within a model plant canopy. Part 1. The turbulence structure. Boundary-Layer Meteorol. 35, 21–52.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.Google Scholar
Raupach, M. R. & Shaw, R. H. 1982 Averaging procedures for flow within vegetation canopies. Boundary-Layer Meteorol. 22, 79–90.Google Scholar
Reynolds, R. T., Hayden, P., Castro, I. P. & Robins, A. G. 2007 Spanwise variations in nominally two-dimensional rough-wall boundary layers. Exp. Fluids 42, 311–320.Google Scholar
Robinson, S. K. 1991 Coherent motions in the turbulent boundary layer. Annu. Rev. Fluid Mech. 23, 601–639.Google Scholar
Rogers, M. M. & Moin, P. 1987 The structure of the vorticity field in homogeneous turbulent flows. J. Fluid Mech. 176, 33–66.CrossRefGoogle Scholar
Rogers, M. M. & Moser, R. D. 1994 Direct simulation of a self-similar turbulent mixing layer. Phys. Fluids 6, 903–923.Google Scholar
Shaw, R. H., Brunet, Y., Finnigan, J. J. & Raupach, M. R. 1995 A wind tunnel study of air flow in waving wheat: two-point velocity statistics. Boundary-Layer Meteorol. 76, 349–376.CrossRefGoogle Scholar
Shaw, R. H. & Patton, E. G. 2003 Canopy element influences on resolved- and subgrid-scale energy within a large-eddy simulation. Agric. Forest Meteorol. 115, 5–17.CrossRefGoogle Scholar
Shaw, R. H, Paw U. K. T., Zhang, X. J., Gao, W., Den hartog, G. & Neumann, H. H. 1990 Retrieval of turbulent pressure fluctuations at the ground surface beneath a forest. Boundary-Layer Meteorol. 50, 319–338.CrossRefGoogle Scholar
Shaw, R. H. & Schumann, U. 1992 Large-eddy simulation of turbulent flow above and within a forest. Boundary-Layer Meteorol. 61, 47–64.Google Scholar
Shaw, R. H., Tavanger, J. & Ward, D. P. 1983 Structure of the Reynolds stress in a canopy layer. J. Climate Appl. Meteorol. 22, 1922–1931.2.0.CO;2>CrossRefGoogle Scholar
Stuart, J. T. 1967 On finite amplitude oscillations in laminar mixing layers. J. Fluid Mech. 29, 417–440.Google Scholar
Sullivan, P. P., Horst, T. W., Lenschow, D. H., Moeng, Chin-Hoh & Weil, J. C. 2003 Structure of subfilter-scale fluxes in the atmospheric surface layer with application to large-eddy simulation modelling. J. Fluid Mech. 482, 101–139.Google Scholar
Sullivan, P. P. & Patton, E. G. 2008 A highly parallel algorithm for turbulence simulations in planetary boundary layers: results with meshes up to 10243. Paper No. 11B5. In Proceedings of 18th American Meteorological Society Symposium on Boundary Layers and Turbulence. 9–13 June 2008, Stockholm, Sweden.Google Scholar
Theordorsen, T. 1952 Mechanism of turbulence. In Proceedings of Second Midwestern Conference on Fluid Mechanics. Ohio State University, Columbus, OH.Google Scholar
Thom, A. S. Stewart, J. B., Oliver, H. R. & Gash, J. H. C. 1975 Comparison of aerodynamic and energy budget analysis of fluxes over a pine forest. Quart. J. R. Meteorol. Soc. 101, 93–105.Google Scholar
Tomkins, C. D. & Adrian, R. J. 2003 Spanwise structure and scale growth in turbulent boundary layers. J. Fluid. Mech. 490, 37–74.Google Scholar
Townsend, A. A. 1976 The Structure of Turbulent Shear Flow. Cambridge University Press.Google Scholar
Watanabe, W. 2004 Large-eddy simulation of coherent turbulence structures associated with scalar ramps over plant canopies. Boundary-Layer Meteorol. 112, 307–341.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
Widnall, S. E. 1975 The structure and dynamics of vortex filaments. Annu. Rev. Fluid Mech. 7, 141–165.Google Scholar
Winant, C. & Browand, F. 1974 Vortex pairing, the mechanism of turbulent mixing layer growth at moderate Reynolds number. J. Fluid Mech. 63, 237–255.Google Scholar
Wyngaard, J. C. 1982 Boundary layer modelling. In Atmospheric Turbulence and Air Pollution Meteorology (ed. Nieuwstadt, F. T. M. & van Dop, H.), pp. 69–106, Reidel.Google Scholar
Zhang, S. & Choudhury, D. 2006 Eigen helicity density: a new vortex identification scheme and its application in accelerated inhomogeneous flows. Phys. Fluids 18 058104-1–058104-4.Google Scholar
Zhou, J., Adrian, R. J., Balachandar, S. & Kendall, T. M. 1999 Mechanisms for generating coherent packets of hairpin vortices in channel flow. J. Fluid Mech. 387, 353–396.Google Scholar