Abstract
The integral length-scalesL for the three orthogonal components of diffusivityK=σL are derived from spectral analysis of velocity time series measurements. A 3-D sonic anemometer was used to make these velocity measurements at heights in the range 0.7–7.0 m in and above a 2 m orchard canopy with near-neutral atmospheric boundary-layer stability conditions. The integral length-scale is compared with another length-scale of diffusionL ∈ obtained by fitting an exponential model to the auto-correlation spectrumR E (t) in the region 0.95<R E (t)<0.5 for smallt. This length-scale is appropriate to a high frequency region of the energy spectrum where turbulent momentum transport becomes diffusion-like and the turbulent energy varies with the inverse square of frequence. This region has been shown by others to determine the magnitude of the dissipation rate of turbulent energy by the action of viscosity even though the dominant dynamics are inviscid. Within the crop, the ratio of the length-scalesL/L ∈ were found to be smaller than the values measured above the crop for vertical turbulence. This was attributed to the enhanced decay rate of turbulent energy due to the effect of the airflow interaction with the crop. It is unclear whether similar effects are present in the horizontal plane because of greater scatter in the data, resulting from the more variable nature of the wind direction in the horizontal plane.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Amiro, B. D.: 1990, ‘Drag Coefficients and Turbulence Spectra Within Three Boreal Forest Canopies’,Boundary-Layer Meteorol. 52, 227–246.
Batchelor, G. K., Binnie, A. M. and Phillips, O. M.: 1955, ‘The Mean Velocity of Discrete Particles in Turbulent Flow in a Pipe’,Proc. Phys. Soc. BLXVIII, 1095.
Baldocchi, D. D. and Hutchison, B. A.: 1988, ‘Turbulence in an Almond Orchard: Spatial Variations in Spectra and Coherence’,Boundary-Layer Meteorol. 42, 293–311.
Corrsin, S.: 1963, ‘Estimates of the Relations Between Eulerian and Lagrangian Scales in Large Reynolds Number Turbulence’,Adv. Geophys. 18A, 25–60.
Hinge, J. O.: 1975, Turbulence, 2nd edn; McGraw-Hill Inc. New York.
Hunt, J. C. R. and Carruthers, D. J.: 1990, ‘Rapid Distortion Theory and the ‘Problem’ of Turbulence’,J. Fluid Mech. 212, 497–532.
Kaimal, J. C. and Kristensen, L.: 1991, ‘Time Series Tapering for Short Data Samples’,Boundary-Layer Meteorol. 57, 187–194.
Lumley, J. L.: 1957, ‘Some Problems Connected with the Motion of Small Particles in Turbulent Fluid’, Dissertation for Doctor of Philosophy at John Hopkins University, Baltimore.
Massey, B. S.: 1970, ‘Mechanics of Fluids’, 2nd Edition, Van Nostrand Reinhold Company Ltd., London, p. 289.
Meyers, T. P. and Baldocchi, D. D.: 1991, ‘The Budgets of Turbulent Kinetic Energy and Reynolds Stress Within and Above a Deciduous Forest’,Agricul. Forest Meteorol. 53, 207–222.
Meyers, T. P. and Paw, K. T.: 1986, ‘Testing of a Higher-Order Closure Model for Modeling Airflow Within and Above Plant Canopies’,Boundary-Layer Meteorol. 37, 297–311.
McCartney, H. A. and Shaw, R. H.: 1985, ‘Gust Penetration into Plant Canopies’,Atmos. Envir. 19(5), 827–830.
Monin, A. S. and Yaglom, A. M.: 1971,Statistical Theory of Turbulence, Vol. II, MIT Press. Cambridge.
Press, W. H., Flannery, B. P., Teukols, S. A. and Vetterling, W. T.: 1986, ‘Numerical Recipes: The Art of Scientific Computing’, Cambridge University Press, pp. 381–453.
Raupach, M. R.: 1988, ‘Canopy Transport Processes’, in: W. L. Steffen and O. T. Denmead (eds.),Flow and transport in the Natural Environment: Advance and Application, Springer Verlag, Berlin.
Raupach, M. R., Coppin, P. A. and Legg, B. J.: 1986, ‘Experiments on Scalar Dispersion Within a Model Plant Canopy, Part 1: The Turbulent Structure’,Boundary-Layer Meteorol. 35, 21–52.
Raupach, M. R. and Shaw, R. H.: 1982, ‘Averaging Procedure for Flow Within Vegitative Canopies’,Boundary-Layer Meteorol. 22, 79–90.
Raupach, M. R. and Thom, A. S.: 1981, ‘Turbulence in and Above Plant Canopies’,Ann. Rev. Fluid Mech. 13, 97–129.
Ruck, B. and Adams, E.: 1991, ‘Fluid Mechanical Aspects of the Pollutant Transport to Coniferous Trees’,Boundary-Layer Meteorol. 56, 163–195.
Shaw, R. H. and Seginer, I.: 1985, ‘The Dissipation of Turbulence in Plant Canopies’,7th Symposium on Turbulence and Diffusion, American Meteorol. Soc., Boston, MA, pp. 200–203.
Shaw, R. H., Silverside, R. H. and Thurtell, G. M.: 1974, ‘Some Observations of Turbulence and Turbulent Transport Within and Above Plant Canopies’,Boundary-Layer Meteorol. 5, pp. 429–449.
Snyder, W. H. and Lumley, J. L.: 1971, ‘Some Measurements of Particle Velocity Autocorrelation Function in a Turbulent Flow’,J. Fluid Mech. 48, pp. 41–71.
Steinke, W. E. and Yates, W. E.: 1989, ‘Modifying Gaussian Models to Obtain Improved Drift Predictions’, paper No 891525 ASAE meeting Marriott New Orleans.
Svensson, U. and Haggkvist, K.: 1990, ‘A Two-Equation Turbulence Model for Canopy Flows’,J. Wind Eng. Indus. Aerodynamics 35, 201–211.
Taylor, G. I.: 1921, ‘Diffusion by Continuous Movements’,Proc. London Math. Soc., A20, pp. 169–212.
Tennekes, H. and Lumley, J. L.: 1971,A First Course in Turbulence, MIT Press, Cambridge, MA.
Unsworth, M. H. and Wilshaw, J. C.: 1989, ‘Wet, Occult and Dry Deposition of Pollutants on Forests’,Agric. Forest Meteorol. 47, 221–238.
Walklate, P. J.: 1983, ‘A Holographic Technique for the Study of Heat Transfer from Rib Roughened Surfaces’,Proceedings of the Third International Symposium on Flow Cisualization, University of Michigan, Ann Arbor Sept. 6–9, pp. 763–771.
Wilson, J. D., Ward, D. P., Thurtell, G. W. and Kidd, G. E.: 1982, ‘Statistics of Atmospheric Turbulence Within and Above a Corn Canopy’,Boundary-Layer Meteorol. 24, 495–519.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Walklate, P.J. The effect of orchard crop structure on the integral length-scale of turbulence. Boundary-Layer Meteorol 63, 1–22 (1993). https://doi.org/10.1007/BF00705374
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00705374