Abstract
Large-eddy simulation is used to reproduce neutrallystratified airflow inside and immediately above a vegetation canopy. A passive scalaris released from the canopy and the evolution of scalar concentration above the canopyis studied. The most significant characteristic of the scalar concentration is the repeatedformation and dissipation of scalar microfronts, a phenomenon that has been observedin nature. These scalar microfronts consist of downstream-tilted regions of highscalar concentration gradients. Computer visualization tools and a conditional samplingand compositing technique are utilized to analyze these microfronts. Peaks in positivepressure perturbation exceeding an experimental threshold are found to be effectiveindicators of scalar microfronts. Convergence of the streamwise velocity componentand divergence of the cross-stream velocity component are observed in the immediatevicinity of scalar microfronts, which helps explain their relatively longlifetimes. Many of these three-dimensional features have been observedin previous field studies of canopy flow.
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References
Brown, K. W. and Covey, W.: 1966, 'The Energy-Budget Evaluation of the Micro-Meteorological Transfer Process within a Corn Field', Agric. Meteorol. 3, 73–96.
Brunet, Y. and Irvine, M. R.: 2000, 'The Control of Coherent Eddies in Vegetation Canopies: Streamwise Structure Spacing, Canopy Shear Scale and Atmospheric Stability', Boundary-Layer Meteorol. 94, 139–163.
Deardorff, J. W.: 1980, 'Stratocumulus-Capped Mixed Layers Derived from Three-Dimensional Model', Boundary-Layer Meteorol. 18, 495–527.
Dwyer, M. J., Patton, E. G., and Shaw, R. H.: 1997, 'Turbulent Kinetic Energy Budgets from a Large-Eddy Simulation of Airflow above and within a Forest Canopy', Boundary-Layer Meteorol. 84, 23–43.
Finnigan, J. J.: 1979, 'Turbulence inWavingWheat. II Structure of Momentum Transfer', Boundary-Layer Meteorol. 16, 213–236.
Gao, W., Shaw, R. H., and Paw U, K. T.: 1989, 'Observation of Organized Structure in Turbulent Flow within and above a Forest Canopy', Boundary-Layer Meteorol. 47, 349–377.
Kikuchi, T. and Chiba, O.: 1985, 'Step-Like Temperature Fluctuations Associated with Inverted Ramps in a Stable Surface Layer', Boundary-Layer Meteorol. 31, 51–63.
Moeng, C.-H.: 1984, 'A Large-Eddy-Simulation Model for the Study of Planetary Boundary-Layer Turbulence', J. Atmos. Sci. 41, 2052–2062.
Moeng, C.-H. and Wyngaard, J. C.: 1988, 'Spectral Analysis of Large-Eddy Simulation of the Convective Boundary Layer', J. Atmos. Sci. 45, 3573–3587.
Patton, E. G.: 1997, Large-Eddy Simulation of Turbulent Flow above and within a Plant Canopy, Ph.D. Dissertation, University of California, Davis, CA, 125 pp.
Patton, E. G., Shaw, R. H., Judd, M. J., and Raupach, M. R.: 1998, 'Large-Eddy Simulation of Windbreak Flow', Boundary-Layer Meteorol. 87, 275–306.
Paw U, K. T., Brunet, Y., Collineau, S., Shaw, R. H., Maitani, T., Qiu, J., and Hipps, L.: 1992, 'On Coherent Structures in Turbulence above and within Agricultural Plant Canopies', Agric. For. Meteorol. 61, 55–68.
Qiu, J., Paw U, K. T., and Shaw, R. H.: 1995, 'Pseudo-Wavelet Analysis of Turbulent Patterns in Three Vegetation Layers', Boundary-Layer Meteorol. 72, 177–204.
Raupach, M. R., Finnigan, J. J., and Brunet, Y.: 1989, 'Coherent Eddies in Vegetation Canopies', in preprint, Fourth Australasian Conference on Heat and Mass Transfer, University of Canterbury, Christchurch, New Zealand, May 9–12, 1989, pp. 75–90.
Raupach, M. R., Finnigan, J. J., and Brunet, Y.: 1996, 'Coherent Eddies and Turbulence in Vegetation Canopies: The Mixing-Layer Analogy', Boundary-Layer Meteorol. 78, 351–382.
Shaw, R. H. and Schumann, U.: 1992, 'Large-Eddy Simulation of Turbulent Flow above and within a Forest', Boundary-Layer Meteorol. 61, 47–64.
Shaw, R. H. and Zhang, X. J.: 1992, 'Evidence of Pressure-Forced Turbulent Flow in a Forest', Boundary-Layer Meteorol. 58, 273–288.
Shaw, R. H., Brunet, Y., Finnigan, J. J., and Raupach, M. R.: 1995, 'A Wind Tunnel Study of Air Flow in Waving Wheat: Two-Point Velocity Statistics', Boundary-Layer Meteorol. 76, 349–376.
Shaw, R. H., Den Hartog, G., and Neumann, H. H.: 1988, 'Influence of Foliar Density and Thermal Stability on Profiles of Reynolds Stress and Turbulence Intensity in a Deciduous Forest', Boundary-Layer Meteorol. 45, 391–409.
Shaw, R. H., Paw, U K. T., Zhang, X. J., Gao, W., Den Hartog, G., and Neumann, H. H.: 1990, 'Retrieval of Turbulent Pressure Fluctuations at the Ground Surface beneath a Forest', Boundary-Layer Meteorol. 50, 319–338.
Su, H.-B., Shaw, R. H., and Paw U, K. T.: 2000, 'Two-Point Correlation Analysis of Neutrally Stratified Flow within and above a Forest from Large-Eddy Simulation', Boundary-Layer Meteorol. 94, 423–460.
Sullivan, P. P., McWilliams, J. C., and Moeng, C.-H.: 1994, 'A Subgrid-Scale Model for Large-Eddy Simulation of Planetary Boundary-Layer Flows', Boundary-Layer Meteorol. 71, 247–276.
Zhang, C., Shaw, R. H., and Paw U, K. T.: 1992, 'Spatial Characteristics of Turbulent Coherent Structures within and above an Orchard Canopy', in S. E. Schwartz and W. G. N. Slim (eds.), Precipitation Scavenging and Atmosphere-Surface Exchange, Hemisphere Publishing Co., Washington, pp. 741–752.
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Fitzmaurice, L., Shaw, R.H., Paw U, K.T. et al. Three-Dimensional Scalar Microfront Systems in a Large-Eddy Simulation of Vegetation Canopy Flow. Boundary-Layer Meteorology 112, 107–127 (2004). https://doi.org/10.1023/B:BOUN.0000020159.98239.4a
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DOI: https://doi.org/10.1023/B:BOUN.0000020159.98239.4a