Abstract
A three-prong spruce twig was modeled as three independent circular cylinders as part of a wind tunnel study of the drag and wake characteristics of twigs in flow velocities ranging from 0.5 to 4.5 m s-1. Using this model, the wake structure and twig drag were explained and length scales describing the microscale wake turbulence were proposed.
Results indicate that the drag force on the twig is influenced by the two flow regimes within the range of velocities studied. The two flow regimes are separated by an apparent shift in the flow field evidenced by a rapid change in the drag coefficient at approximately 1.5 m s-1. For the low velocity regime (0.5 to 1.5 m s-1), the flow ‘sees’ a highly porous twig-cylinder with pores a function of the inter-needle spacing and a length scale related to the needle length. For the high velocity regime (1.5 to 4.5 m s-1), the flow ‘sees’ a twig-cylinder with low porosity and a dominant length scale related to the twig needle-tip to needle-tip diameter.
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References
Allen, L. H., Jr.: 1968, ‘Turbulence and Wind Speed Spectra within a Japanese Larch Plantation’, J. Appl. Meteorol. 7, 73–78.
Arkin, G. F. and Perrier, E. R.: 1974, ‘Vorticular Air Flow within an open Row Crop Canopy’, Agric. Meteorol. 13, 359–374.
Baines, G. B. K.: 1972, ‘Turbulence in Wheat Crop’, Agric. Meteorol. 10, 93–105.
Bruun, H. H. and Davies, P. O. A. L.: 1972, ‘Measurements of Turbulent Quantities by Single hot Wires and X hot Wires Using Digital Evaluation Techniques’, in D. J. Cockrell (ed.), Fluid Dynamics Measurements in the Industry and Medical Environment, Vol. 1, Leicester Press, Surry GB, pp. 163–166.
Bull, G. A. D. and Reynolds, E. R. C.: 1968, ‘Wind Turbulence Generated by Vegetation and its Implications’, Suppl. to Forestry, Journal of the Society of Foresters of Great Britain 28–37.
Castro, I. P.: 1971, ‘Wake Characteristics ofTwo-Dimensional Perforated Plates Normal to an Air Stream’, J. Fluid Mech. 46, 599–609.
Cionco, R. M.: 1965, ‘A Mathematical Model for Air Flow in a Vegetative Canopy’, J. Appl. Meteorol. 4, 517–522.
Goldstein, S. (ed.): 1938, Modern Developments in Fluid Mechanics. Vol. II, Clarendon Press, Oxford.
Guyot, G.: 1978, ‘Determination des efforts exerces par le vent sur un brise-vent’, Boundary-Layer Meteorol. 15, 57–67.
Inoue, E.: 1963, ‘On the Turbulent Structure of Airflow within Crop Canopies’, J. Meteorol. Soc. Japan 41, 317–325.
Isobe, S.: 1972, ‘A spectral Analysis of Turbulence in a Corn Canopy’, Bull. Natl. Inst. Agric. Sci. (Japan Ser. A.) 19, 101–112.
Jarvis, P. G., James, G. B., and Landsberg, J. J.: 1976, ‘Coniferous Forest’, in Monteith, J. L. (ed.), Vegetation and the Atmosphere Vol. 2, Academic Press, London, pp. 171–240.
Landsberg, J. J. and Powell, D. B. B.: 1983, ‘Surface Exchange Characteristics of Leaves Subject to Mutual Interference’, Agric. Meteorol. 12, 169–184.
Landsberg, J. J. and Thom, A. S.: 1971, ‘Aerodynamic Properties of a Plant of Complex Structure’, Quart. J. Roy. Meteorol. Soc. 97, 565–570.
Mair, W. A. and Maull, D. J.: 1971, ‘Bluff Bodies and Vortex Shedding- a Report on Euromech 17’, J. Fluid Mech. 45, 209–224.
Majola, O. O.: 1974, ‘A Hot Wire Method for Three Dimensional Shear Flows’, DISA Information 16, 11–14.
McBean, G. A.: 1968, ‘An Investigation of Turbulence within the Forest’, J. Appl. Meteorol. 7, 410–416.
Meroney, R. N.: 1968, ‘Characteristics of Wind and Turbulence in and above Model Forests’, J. Appl. Meteorol. 7, 410–416.
Perrier, E. R., Robertson, J. M., Mulligan, R. J., and Peters, D. B.: 1972, ‘Spatial and Temporal Variation of Wind above and within a Soybean Canopy’, Agric. Meteorol. 10, 421–442.
Plate, E. J.: 1971, ‘The Aerodynamics of Shelterbelts’, Agric. Meteor. 8, 203–222.
Raupach, M. R. and Thom, A. S.: 1981, ‘Turbulence in and above Plant Canopies’, Ann. Rev. Fluid Mech. 13, 97–129.
Roshko, A.: 1954, ‘On the Drag and Shedding Frequency of Two-Dimensional Bluff Bodies’, NACA Report No. 1191.
Saito, T., Nagai, Y., Isobe, S., and Horibe, Y.: 1970, ‘An Investigation of Turbulence within a Corn Canopy’, (Japanese, english summary), J. Agric. Meteorol. (Tokyo) 25, 205–214.
Seginer, I.: 1974, ‘Aerodynamic Roughness of Vegetated Surfaces’, Boundary-Layer Meteorol. 5, 383–393.
Seginer, I., Mulhearn, P. J., Bradley, E. F., and Finnigan, J. J.: 1976, ‘Turbulent Flow in a Model Plant Canopy’, Boundary-Layer Meteorol. 10, 423–453.
Schuepp, P.: 1982, ‘Laboratory Studies on Dry Deposition of Sub Micron — Size Particles on Coniferous Foliage’, Boundary-Layer Meteorol. 24, 465–480.
Silversides, R. H.: 1974, ‘On Scaling Parameters for Turbulence Spectra within Plant Canopies’, Agric. Meteorol. 13, 203–211.
Surry, J.: 1965, ‘Experimental Investigation of the characteristics of Flow about Curved Circular Cylinders’, Univ. Toronto Inst. for Aero. Studies Tech. note No. 89.
Surry, J. and Surry, D.: 1967, ‘The Effect of Inclination on the Strouhal Number and Other Wake Properties of Circular Cylinders at Sub-critical Reynolds Numbers’, Univ. Toronto Inst. for Aero. Studies Tech. note No. 116.
Tibbals, E. C., Carr, E. K., Gates, D. M., and Kreith, F.: 1964, ‘Radiation and Convection in Conifers’, Am. J. Bot. 51, 527–538.
Zaman, K. B. M. Q. and Hussain, A. K. M. F.: 1981, ‘Taylor's Hypothesis and Large Scale Coherent Structures’, J. Fluid. Mech. 112, 379–396.
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Grant, R.H. The scaling of flow in vegetative structures. Boundary-Layer Meteorol 27, 171–184 (1983). https://doi.org/10.1007/BF00239613
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DOI: https://doi.org/10.1007/BF00239613