Wind tunnel protocol for spray drift assessment

Ch. Stainier, F. Lebeau, Destain M.-F., Schiffers B.

Introduction

• The objective of wind tunnel protocol is to measure spray drift in a reproducible way in order to evaluate the relative drift potential of: – different spray nozzles– different operating parameters (Pressure,

Height,…)– different formulation and adjuvants

Introduction

• A normalisation process is underway at the international level: ISO/DIS 22856/1 within TC23/SC6. It defines: – Typical wind tunnel design and layout (2*2m section,

measurement section)– Examples of measurement methods– Wind turbulence and heterogeneity thresholds– Wind tunnel instrumentation (humidity, wind speed,

temperature)– Typical test reports

Introduction• Some major hurdles remain as the ISO/DIS

22856/1 protocol is designed for a static nozzle: – The long axis of flat fan nozzle is set perpendicular to

air flow, what is not representative of field drift condition

– The blockage effect of droplet induced air-flow generate vortexes entraining driftable droplets resulting in a very specific pattern

– The collectors are prone to saturation due to local overdoses

Introduction• The presentation intend to present the

protocol developed in Gembloux which is based on traversing – an ISO/DIS 22856/1 wind tunnel– a moving nozzle with controllable speed– fibre glass ground samples

Closed loop allows the use real formulations

Speed up to 6 m/s

Droplet filter

Low turbidityMoving boom

Large test section

The wind tunnel facility

The wind tunnel controllable parameters

• Wind speed 0 - 6 m/s (more with reduced wind homogeneity)

• Temperature (cooler and heater)

• Relative Humidity (water atomisation)

0.8m 6m

Spray nozzle orientation

Wind direction (2m/s)

Nozzle displacement axis (2m/s)

WIND TUNNEL TEST SECTION

Ground collector

Standard settings : Wind speed = 2m/s

RH = 80% T° = 20°C

P = 3 bar H=50cm

Glass fibre collectors Nozzle speed = 2m/s

The Gembloux measurement protocol (aerial view)

0

20

40

60

80

100

120

-100 0 100 200 300 400 500 600

2m/s 50cm 1

2m/s 50cm 2

2m/s 50cm 3

parameters Mean CV (%)

Wind (m/s) 2.026 0.814

Temp (°C) 19.684 0.137

RH (%) 79.797 0.100

P (bar) 3.093 0.393

FF 110 02 (LU)Results repeatability

0

20

40

60

80

100

120

-100 0 100 200 300 400 500 600

DG 2m/s 1

DG 2m/s 2

DG2m/s 3

DG 2m/s 4

parameters mean CV (%)

Wind (m/s) 1.825 1.162

Temp (°C) 19.207 0.185

RH (%) 78.858 0.177

P (bar) 2.892 0.281

DG 110 04Results repeatability

0

20

40

60

80

100

120

-100 0 100 200 300 400 500 600

XR 2m/s 1

XR 2m/s 2

XR 2m/s 3

parameters mean CV (%)

Wind (m/s) 2.006 1.048

Temp (°C) 19.287 0.125

RH (%) 68.958 0.132

P (bar) 3.029 0.194

XR 110 04Results repeatability

0

20

40

60

80

100

120

140

-100 0 100 200 300 400 500 600

2m/s 50cm 2

1m/s 50cm

4m/s 50cm

FF 110 02 (LU)Results wind speed

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40

60

80

100

120

-100 0 100 200 300 400 500 600

DG 2m/s 2

DG 4m/s

DG 1m/s

DG 110 04Results wind speed

0

20

40

60

80

100

120

-100 0 100 200 300 400 500 600

XR 2m/s 2

XR 4m/s

XR 1m/s

Results wind speed

Conclusion

• Repeatability is very satisfactory

• Small differences can be highlighted

• Other drift measurement methods can be used

• A Gaussian tilting plume model is developed in order to predict drift of a moving nozzle