The relationship between open windspeed and windspeed reduction in shelter |
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| Authors: | H Zhang J R Brandle G E Meyer L Hodges |
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| Institution: | (1) Department of Forestry, Fisheries and Wildlife, University of Nebraska, 68583-0814 Lincoln, NE, USA;(2) Present address: UCLA-DOE Laboratory, University of California, 900 Veteran Avenue, 90024-1786 Los Angeles, CA, USA;(3) Department of Biological Systems Engineering, University of Nebraska, 68583-0726 Lincoln, NE, USA;(4) Department of Horticulture, University of Nebraska, 68583-0724 Lincoln, NE, USA |
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| Abstract: | Windspeed reduction in shelter is generally expressed relatively and is usually assumed to be independent of open windspeed. The purpose of this study was to re-examine the relationship between open windspeed and windspeed reduction in shelter using windspeeds and wind directions measured for two windbreak systems at various distances from the windbreaks and with three windbreak porosities. Optical windbreak porosities were estimated from digitized color photographs using an intelligent (trainable) image processing program. Relative windspeed reduction in shelter was found to be related to the open windspeed. There existed a threshold windspeed at approximately 5 m s–1, below which relative windspeed reduction varied but generally decreased as the open windspeed increased. Above the threshold windspeed, open windspeed did not have an effect on relative windspeed reduction in the sheltered zone. Using the threshold windspeed reduction, the authors propose an index to evaluate the effectiveness of a windbreak for the overal windspeed protection.Published as Journal Series No. 10815 of the Agricultural Research Division, University of Nebraska. |
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| Keywords: | relative windspeed reduction shelterbelt windbreaks windspeed |
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