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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Agroforestry systems 29 (1995), S. 191-200 
    ISSN: 1572-9680
    Schlagwort(e): windbreaks ; shelterbelt ; wind ; model ; specific protection efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effectiveness of windbreaks in windspeed reduction is often evaluated without regard to the objects to be protected. In fact, many objects may have different sensitivities to wind and often require different degrees of wind protection. Since commonly used indexes do not consider the sensitivity to wind, a concept of specific protection efficiency is developed. A critical windspeed is used to represent the sensitivity of each object. Windspeeds greater than this value are considered damaging. A dimensionless protection index is defined to evaluate windbreak efficiency. The maximum index value is 1 for the highest protection, and the index is negative when sheltered windspeed is greater than the critical windspeed. This index can be compared, summed, and averaged across different windbreaks, objects, and leeward locations. A sample of critical windspeed values was compiled from the literature. The index was evaluated using actual wind data measured under both sheltered and open conditions. The results indicated that the index can be used for evaluating windbreak effectiveness in terms of objects protected under various conditions. This model could be used as a tool for windbreak-related research and policy making.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Agroforestry systems 32 (1995), S. 297-311 
    ISSN: 1572-9680
    Schlagwort(e): relative windspeed reduction ; shelterbelt ; windbreaks ; windspeed
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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