Measuring Sub-Second Wind Velocity Changes at One Meter above the Ground

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2016-01-01
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Hanna, H. Mark
Extension Agricultural Engineer
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Darr, Matthew
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Hoff, Steven
Professor Emeritus
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Steward, Brian
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Agricultural and Biosystems Engineering

Since 1905, the Department of Agricultural Engineering, now the Department of Agricultural and Biosystems Engineering (ABE), has been a leader in providing engineering solutions to agricultural problems in the United States and the world. The department’s original mission was to mechanize agriculture. That mission has evolved to encompass a global view of the entire food production system–the wise management of natural resources in the production, processing, storage, handling, and use of food fiber and other biological products.

History
In 1905 Agricultural Engineering was recognized as a subdivision of the Department of Agronomy, and in 1907 it was recognized as a unique department. It was renamed the Department of Agricultural and Biosystems Engineering in 1990. The department merged with the Department of Industrial Education and Technology in 2004.

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1905–present

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  • Department of Agricultural Engineering (1907–1990)

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Agricultural and Biosystems Engineering
Abstract

Agricultural spray drift is affected by many factors including current weather conditions, topography of the surrounding area, fluid properties at the nozzle, and the height at which the spray is released. During the late spring/summer spray seasons of 2014 and 2015, wind direction, speed, and solar radiation (2014 only) were measured at 10 Hz, one meter above the ground to simulate conditions that are present for a droplet. Measurements of wind velocity as the wind passed from an upwind sensor to a downwind sensor were used to evaluate under what conditions wind may be most likely to have a significant direction or speed change which affects droplet trajectory. For two individual datasets in which the average wind speed was 3.6 m/s and 1.5 m/s, it was found that there existed little linear correlation of wind speed or wind direction between an upwind and downwind anemometer separated by 30.5 meters (100 ft). The highest observed correlation, resulting from a 12 second lag between the upwind and downwind datasets, was 0.29 where the average wind speed was 3.6 m/s. Correlations were only found for wind speeds exceeding 3 m/s. Using this lag time, it was observed that the wind direction 30 seconds into the future had a 30% chance to be different by more than 20 degrees from current conditions. While a wind speed difference of more than 1 m/s from current conditions (mean wind speed was 3.6 m/s) happened about 50% of the time. Looking at 2014 and 2015 spray season data, it was found that the most variability occurred with wind speeds below 2 m/s.

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This paper appeared in 2016 ASABE Annual International Meeting, Paper No. 162461726, pages 1-15 (doi: 10.13031/aim.20162461726). St. Joseph, Mich.: ASABE.. Posted with permission.

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