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Comparison of a random-walk model for droplet transport and wind-tunnel measurements

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Academic year: 2021

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(1)

Comparison of a random-walk model

for droplet transport and wind-tunnel

measurements

Nicolas De Cock, Mathieu Massinon, Sofiene Ouled Taleb

(2)

Application of plant protection products

𝑊𝑒 = 𝜌𝒗&𝒍 𝜎

Deposition

From the nozzle to the plant èSmall droplets are more prone to drift

Retention

Droplet impacts on the plant surface èLarge droplets have more energy when impacting the leaf surface

(3)
(4)

Random-walk model

fluctuations mean fluctuations Set as constant in the wind tunnel RMS of the horizontal velocity Random value [-1:1] Lagrangian time Time step

(5)

Goals

Compare numerical simulations of the transport of a

spray with measurements in wind tunnel

Spray from single jet break-up

(6)

Wind tunnel

Speed up to 6 m/s Droplet filter Large test section Moving boom 2 x 2 x 8 m

(7)

Reduced span spray

Experimental set-up

(8)

Reduced span spray

Experimental parameters

• Droplet velocity: 8.5 m/s • Liquid: Tap water + nigrosin (black dye) • Wind speed: 2 m/s with 5% turbulence intensity • Humidity of 60% and temperature of 20°C

Droplet size distribution

Rayleigh break-up

(9)

Reduced span spray

Experiment Simulation • Top picture of the collecting paper • Impact of 5000 droplets • Marker sizes have been adapted to the droplet diameter

(10)
(11)

F/M spray

Experimental parameters

• Nozzle: 110-03 at 3 bars crossing the test section at 2m/s • Liquid: Tap water + nigrosin (black dye) • Wind speed: 2 m/s with 5% turbulence intensity • Humidity of 60% and temperature of 20°C 7 m Droplet size distribution

(12)

F/M spray

Experiment

Simulation

Relative impact density in

respect to the distance

• Impact of 100 000 droplets High density of impact èissue to identify individual droplet

(13)

F/M spray

Relative impact area in respect to the

distance from the nozzle

Relative proportion of black pixels Relative proportion of droplet areas

(14)

F/M spray

Travelled distance in respect for

different droplet size

(15)

Conclusions

Conclusions

Simulation and the experiment showed qualitative

agreement

Paper combined with dye provides an interesting

spatial information about droplet deposition

Perspective

Comparison of the droplet velocity before impaction

Improvement of the experimental data processing

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