#AAAR2022 Spray Droplet Size in Liquid Sheets Containing Surfactants and Oil Emulsions. IAROSLAV MAKHNENKO, Long Nguyen, Cari Dutcher, Christopher J. Hogan, Elizabeth Alonzi, Christine Colby, Steven Fredericks, University of Minnesota
Agricultural spraying - spraying drift is a problem. 30% of all complaints come from this phenom. Droplets are traveling long distances airborne.
100-150 micron droplets.
Need to prevent spray drift: Trees around your field.
100-150 micron droplets.
Need to prevent spray drift: Trees around your field.
droplet size distribution - controls -
Chemical composition and Nozzle type
Chemical composition and Nozzle type
Things to think about in this space:
Nozzles...
Viscoelasticity - stabilize the liquid sheath.
Surface tension is also important. Higher surface tensions tend to make bigger droplets.
inhomogeneities -
Nozzles...
Viscoelasticity - stabilize the liquid sheath.
Surface tension is also important. Higher surface tensions tend to make bigger droplets.
inhomogeneities -
Wind tunnel exps.
Laser diffraction to get at the size distribution
Resolve the size distribution in situ.
Study RO water, and surfactant
Need metric. Volume mean diameter. Half larger half smaller.
Laser diffraction to get at the size distribution
Resolve the size distribution in situ.
Study RO water, and surfactant
Need metric. Volume mean diameter. Half larger half smaller.
We want to identify the impact of oil emulsions on size distribution.
Once we add more and more oil we see increase in droplet size and decrease in fraction of small droplets.
After we reach 1% oil concentration, rate of decrease in small stuff declines.
Once we add more and more oil we see increase in droplet size and decrease in fraction of small droplets.
After we reach 1% oil concentration, rate of decrease in small stuff declines.
Concentration of surfactant in system: How does surfactant impact the distribution.
Initially added - no effect
Later as we went up and up in surfactant conc. we see increase in the droplet size
Initially added - no effect
Later as we went up and up in surfactant conc. we see increase in the droplet size
Combination of water and oil in the system. Fix the amount of oil and then keep adding surfactant.
Surprising results - increase in volume mean diameter and then decrease. With small conc helps stabilize - effects the break-up to minimize the small droplets.
Surprising results - increase in volume mean diameter and then decrease. With small conc helps stabilize - effects the break-up to minimize the small droplets.
Basically need to find the goldilocks amount of oil and surfactants to optimize droplet size distribution.
How to visualize droplets on the leaf surface (you know the whole point of spraying the crops in the first place).
What's uptake time-scale (leaf drinking the droplet)
So... we need to also incorporate an RH stage to stimulate different ambient conditions. All in the lab.
What's uptake time-scale (leaf drinking the droplet)
So... we need to also incorporate an RH stage to stimulate different ambient conditions. All in the lab.
So we measure dew point and temp / dial in whatever RH we want.
Took some neat videos. Calibrated NaCl and leverage the water uptake and growth we expect as f(RH). ~ 70-75% RH - and boom - NaCl takes up all the water.
Took some neat videos. Calibrated NaCl and leverage the water uptake and growth we expect as f(RH). ~ 70-75% RH - and boom - NaCl takes up all the water.
Pretty astounding to see how a 50-100 micron spray droplet can travel beyond the perimeter of an agricultural field and pose problems for those downwind.
Even (REALLY BIG) particles can remain airborne over long distances
Even (REALLY BIG) particles can remain airborne over long distances
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