The MIIS Eprints Archive

Mathematical Modelling of the Impact of Liquid Properties on Droplet Size from Flat Fan Nozzles

Al-Izzi, Sami and Broggi, Francesco and Cimpeanu, R. and Connellan, Lloyd and Gowers, Robert and Hunt, Mat and Lunz, Davin and Moore, Matthew and Ockendon, John and Pereira, Victoria and Sprittles, James and Warrington, Rachael (2017) Mathematical Modelling of the Impact of Liquid Properties on Droplet Size from Flat Fan Nozzles. [Study Group Report]

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Flat fan nozzles atomize crop protection products, breaking them into droplets. Droplet size matters - smaller droplets give better perfor- mance, but very small droplets drift. We want to use mathematical models to better understand how liquid properties affect droplet size.
There are three types of breakup: wavy sheet, perforation, and rim. In wavy sheet breakup, increasing viscosity or surface tension increases droplet size. To investigate further, we carry out direct numerical simulations of jet breakup, which show that suface tension has little effect, but increasing viscosity leads to fewer droplets. Decreasing the jet velocity also results in fewer droplets, with a wider size distribution.
Each type of breakup involves primary breakup into cylinders of fluid, then secondary breakup into droplets. We thus consider the breakup of a cylinder of fluid. Direct numerical simulations suggest that within the tested parameter range viscosity has little impact on droplet size, however it does influence the timescale on which the instability evolves considerably. Linear stability analysis suggests that increasing viscosity increases the wavelength of the most unstable mode, which we expect leads to larger droplets, and that it reduces the rate of breakup.
Perforations - holes in the sheet - also lead to breakup. We find how the length fraction of the sheet that is void changes with time.
After breakup, the droplets continue to evolve. We develop a model, based on a transport equation, for this process. A key parameter is the breakup rate constant - larger values lead to more breakup, fewer large droplets, and a narrower size distribution.
Together, these mathematical approaches improve our understanding of how droplets form, and can be used to guide experimental work.

Item Type:Study Group Report
Problem Sectors:Fluids
Study Groups:European Study Group with Industry > ESGI 130 (Warwick, UK, Sep 4-8, 2017)
UK Study Groups > ESGI 130 (Warwick, UK, Sep 4-8, 2017)
Company Name:Syngenta
ID Code:751
Deposited By: Bogdan Toader
Deposited On:21 Jan 2019 22:44
Last Modified:21 Jan 2019 22:44

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