Field Study of Wind Through and Over a Forest Edge PDF Download
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Author: D. R. Miller
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
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Book Description
Three-dimensional miniature wind sensors that are stationary and have a high frequency response were developed and used to measure the wind structure inside and outside a forest edge. Extensive data sets were taken at different distances from the edge with the sensors arranged vertically through the canopy on movable towers both inside and outside the edge. Horizontally spaced sensors showed the flow inside the forest was correlated spatially at spacing less than 4 m. More persistent autocorrelations at higher wind speeds demonstrated that larger eddies penetrated the canopy at higher wind speeds. Measurements above the canopy demonstrated a decay of Reynolds stress with decreasing height in the roughness sublayer. Velocity spectra demonstrated that mechanical turbulence is generated by the canopy at frequencies of about 1 hz. Comparisons of in-forest profiles with the wind blowing into and out of the forest showed the effects of the edge on the turbulent intensities, streamwise and cross stream Reynolds stresses. The flow through the edge intensified the turbulences below and above the forest canopy. Conditional sampling analyses demonstrated the sweeping and ejection mechanism of large scale momentum transfer is modified by the edge. Measurements outside the edge show the evolution of intermittent stagnation eddies against the edge.
Author: D. R. Miller
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
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Book Description
Three-dimensional miniature wind sensors that are stationary and have a high frequency response were developed and used to measure the wind structure inside and outside a forest edge. Extensive data sets were taken at different distances from the edge with the sensors arranged vertically through the canopy on movable towers both inside and outside the edge. Horizontally spaced sensors showed the flow inside the forest was correlated spatially at spacing less than 4 m. More persistent autocorrelations at higher wind speeds demonstrated that larger eddies penetrated the canopy at higher wind speeds. Measurements above the canopy demonstrated a decay of Reynolds stress with decreasing height in the roughness sublayer. Velocity spectra demonstrated that mechanical turbulence is generated by the canopy at frequencies of about 1 hz. Comparisons of in-forest profiles with the wind blowing into and out of the forest showed the effects of the edge on the turbulent intensities, streamwise and cross stream Reynolds stresses. The flow through the edge intensified the turbulences below and above the forest canopy. Conditional sampling analyses demonstrated the sweeping and ejection mechanism of large scale momentum transfer is modified by the edge. Measurements outside the edge show the evolution of intermittent stagnation eddies against the edge.
Author:
Publisher:
ISBN:
Category : Military research
Languages : en
Pages : 294
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Book Description
Author: J. D. Lin
Publisher:
ISBN:
Category :
Languages : en
Pages : 116
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Book Description
This study focused on field measurements to determine the spatial variability of the turbulence characteristics under various atmospheric and forest canopy conditions. A high-speed multi-channel data acquisition system was configured and tested. Fixed and movable observation towers have been set up in the University experimental forest in Coventry, Conn. Two wind velocity sensors, being tested and evaluated in the laboratory for their capability to measure the three-dimensional flow with high turbulence intensity that generally characterizes the flow regime in a forest canopy; are a dual triple-split hot-film probe and a tri-diagonal hot-film probe with a wind octant electronic sensor (WOES). The response of WOES tested in the low-speed wind nozzle appears to be promising and its compatibility with the tri-diagonal hot-film probe is being evaluated. A number of field measures has been conducted over and inside the forest canopy, using a vertical array of velocity sensors which includes a propeller anemometer, and x-hot wire and hot film anemometers.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1126
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author:
Publisher:
ISBN:
Category : Forests and forestry
Languages : en
Pages : 258
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Book Description
Author: United States. Army Research Office
Publisher:
ISBN:
Category : Military research
Languages : en
Pages : 296
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Book Description
Vols. for 1977- consist of two parts: Chemistry, biological sciences, engineering sciences, metallurgy and materials science (issued in the spring); and Physics, electronics, mathematics, geosciences (issued in the fall).
Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 1002
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Book Description
Author:
Publisher:
ISBN:
Category : Agroforestry
Languages : en
Pages : 8
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Book Description
Author:
Publisher:
ISBN:
Category : Forests and forestry
Languages : en
Pages : 616
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Book Description
Author: B.A. Hutchison
Publisher: Springer Science & Business Media
ISBN: 9400953054
Category : Science
Languages : en
Pages : 683
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Book Description
The effects of meteorological phenomena upon forest produc tivity and forestry operations have been of concern for many years. With the evolution of system-level studies of forest eco system structure and function in the International Biological Program and elsewhere, more fundamental interactions between forest ecosystems and the atmosphere received scientific atten tion but the emphasis on meteorological and climatological effects on forest processes remained. More recently, as recogni tion has developed of potential and actual problems associated with the atmospheric transport, dispersion, and deposition of airborne pollutants, the effects of forest canopies upon boundary-layer meteorological phenomena has come under scientific scrutiny. Looking to the future, with rising atmospheric con centrations of C02 and increasing competition for the finite fresh-water resources of the earth, interest in the role of forests in global C02 and water balances can also be expected to intensify. Thus, the nature of forest canopy-atmosphere interac tions, that is to say, the meteorological phenomena occurring in and above forest canopies, are of importance to a wide variety of scientific and social-issues. Demands for forest meteorological information currently exceed levels of knowledge and given the economic constraints of science in general and environmental sciences in particular, chances for major improvements in scien tific support in the near future are slim. Unfortunately, studies of environmental phenomena in and above forests are costly and logistically difficult. Trees, the ecological dominants of forest ecosystems, are the largest of all terrestrial organisms.
