caa a22 4500 475777603 CHVBK 20180406123635.0 cr unu---uuuuu 170329e20000601xx s 000 0 eng 10.1023/A:1002693625637 doi (NATIONALLICENCE)springer-10.1023/A:1002693625637 Wind Tunnel And Field Measurements Of Turbulent Flow In Forests. Part I: Uniformly Thinned Stands [Elektronische Daten] [Michael Novak, Jon Warland, Alberto Orchansky, Rick Ketler, Steven Green] Many forest management methods alterstand density uniformly. The effectsof such a change on the wind andturbulence regimes in the forest arecritical to a number of processes governingthe stability of the stand and itsmicroclimate. We measured wind speed andturbulence statistics with a Dantec tri-axialhot-film probe in model forests of variousdensities (31-333 trees m-2), created byremoving whole trees in a regular pattern in awind tunnel, and compared them with similarmeasurements made with propeller anemometers insimilarly thinned plots (156-625 trees ha-1)within a Sitka spruce stand in Scotland. The results agree well, in general, with measurements made inother such studies with diverse canopy types.The systematic variations with density and verticalleaf-area distribution (which differed betweenwind-tunnel and field trees) in our work can explainmuch of the variability shown in scaled profiles ofbasic turbulence statistics reported in theliterature. The wind tunnel and field results are shown to be in good agreement overalldespite the difference in vertical leaf-areadistribution. Within-canopy and isolated-treedrag coefficients in the wind tunnel showthat tree-scale shelter effects increase astree density increases. The measurements indicatethat turbulence in the canopy is dominated bylarge-scale structures with dimensions of the sameorder as the height of the canopy as found inother studies but suggest that inter-tree spacing also modulates the size of these structures. These structures are associated with the sweeps that dominatemomentum exchange in the canopy and it is thisfact that allows the tri-axial probe to operate sowell despite the relatively narrow range of anglesin which the wind vector is correctly measured. Theratio of streamwise periodicity of these structuresto vorticity thickness varies systematically withtree density in the range 2.7-5.1, which spans theexpected range of 3.5-5 found in a laboratorymixing-layer, suggesting that tree spacing imposes another relevant length scale. This test andothers show that the results are in agreement withthe idea that canopy turbulence resembles that of a mixing layer even though they disagree with, and challenge the linear relationship between, streamwise periodicity andshear length scale presented recently in theliterature. The measurements are also in goodoverall agreement with simple drag models presented recently by other researchers. Kluwer Academic Publishers, 2000 Field measurements nationallicence Thinned forests nationallicence Turbulence nationallicence Wind tunnel nationallicence Novak Michael Faculty of Agricultural Sciences, The University of British Columbia, 266B-2357 Main Mall, V6T 1Z4, Vancouver, British Columbia, Canada aut Warland Jon Department of Land Resource Science, University of Guelph, N1G 2W1, Guelph, Ontario, Canada aut Orchansky Alberto Faculty of Agricultural Sciences, The University of British Columbia, 266B-2357 Main Mall, V6T 1Z4, Vancouver, British Columbia, Canada aut Ketler Rick Faculty of Agricultural Sciences, The University of British Columbia, 266B-2357 Main Mall, V6T 1Z4, Vancouver, British Columbia, Canada aut Green Steven The Horticulture and Food Research Institute of New Zealand Ltd., Private Bag 11-030, Palmerston North, New Zealand aut Boundary-Layer Meteorology Kluwer Academic Publishers 95/3(2000-06-01), 457-495 0006-8314 95:3<457 2000 95 10546 https://doi.org/10.1023/A:1002693625637 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1002693625637 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Novak Michael Faculty of Agricultural Sciences, The University of British Columbia, 266B-2357 Main Mall, V6T 1Z4, Vancouver, British Columbia, Canada aut NATIONALLICENCE 700 1- Warland Jon Department of Land Resource Science, University of Guelph, N1G 2W1, Guelph, Ontario, Canada aut NATIONALLICENCE 700 1- Orchansky Alberto Faculty of Agricultural Sciences, The University of British Columbia, 266B-2357 Main Mall, V6T 1Z4, Vancouver, British Columbia, Canada aut NATIONALLICENCE 700 1- Ketler Rick Faculty of Agricultural Sciences, The University of British Columbia, 266B-2357 Main Mall, V6T 1Z4, Vancouver, British Columbia, Canada aut NATIONALLICENCE 700 1- Green Steven The Horticulture and Food Research Institute of New Zealand Ltd., Private Bag 11-030, Palmerston North, New Zealand aut NATIONALLICENCE 773 0- Boundary-Layer Meteorology Kluwer Academic Publishers 95/3(2000-06-01), 457-495 0006-8314 95:3<457 2000 95 10546 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer