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Iowa State University (1994)

Flow past an agricultural shelterbelt : measurements and model results

Adoum Alkhalil

Titre : Flow past an agricultural shelterbelt : measurements and model results

Auteur : Adoum Alkhalil

Université de soutenance : Iowa State University

Grade : Doctor of Philosophy (PhD) 1994

Shelterbelts and windbreaks have been long used to improve crop production by controlling wind damage, preserving soil-moisture, and preventing soil erosion. Many aspects of shelterbelts have been to some extent explored, but there are some contradicting reports in the literature concerning certain issues. ;In this study certain aspects of shelterbelt aerodynamics are investigated. Experimental data are used to study the effects of free stream velocity on the wind-reducing ability of shelterbelts and to test an aerodynamic numerical model. The tested model is then used to explore the controversial issue of windspeed reduction, the extent of protection in the lee and to study the relationship between shelter efficiency and density. ;The data analysis reveals that the incidence angle and the windspeed in the open are negatively correlated to the reduced windspeed in the lee. A significant deflection for oblique winds is found to be consistent with the large pressure gradient observed across shelterbelts. Results of simulations using the tuned model are in good agreement with observed wind profiles. ;Numerical simulations show that the protected leeward distance is larger for medium density shelters than for the very dense ones. The shear stress at the ground is consistent with the simulated wind profiles and in good agreement with previous observations. Overall model performance is satisfactory.


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