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Agricultural spray droplet dispersion in turbulent windflow

Phillips, Jeremy Charles (1998)
Ph.D. thesis, University of Birmingham.

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Abstract

Off-target contamination (or spray drift) during agricultural chemical application, arising from removal of small (diameter < 100 m) droplets from sprays by atmospheric or vehicle-generated cross flows, is investigated experimentally. The primary requirement for realistic wind tunnel studies is identified from background review as matching the full-scale logarithmic man velocity profile with suitable surface roughness parameters. A general calculation scheme is presented for spacing horizontal flat plates to simulate weakly-sheared mean velocity profiles. Adequate full-scale matching of logarithmic mean velocity profiles is achieved after systematic equipment modification. Comparative field and wind tunnel experiments using single nozzles show adequate agreement following the above approach, indicating that air entrained into the liquid spray stabilizes the spray to the cross flow action. Measurements within an agricultural spray in still air show that small droplets are passively transported within the entrained air field, whose characteristic turbulence length scale is too small to contribute to droplet dispersion. Wind tunnel studies employing conventional sprays show small droplet removal associated with regions where the entrained air velocity is less than the cross flow velocity, with essentially passive downwind transport. Numerical simulations of spray drift must clearly incorporate characteristics of the entrained air velocity field.

Type of Work:Ph.D. thesis.
Supervisor(s):Thomas, Neale
School/Faculty:Schools (1998 to 2008) > School of Engineering
Department:Department of Chemical Engineering
Subjects:TP Chemical technology
Institution:University of Birmingham
Library Catalogue:Check for printed version of this thesis
ID Code:1404
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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