Diameter-Resolved Velocity Correction for Laser Diffraction Calibration and Wind Tunnel Measurement of Sprays

Fatigue and aging of electrical overhead transmission lines is a major concern nowadays in developed countries with ever increasing difficulties to build new lines and an already quite aged network. An important degradation phenomenon of overhead line cables is fretting fatigue close to the suspension clamps due to vortex induced vibrations (VIV). These VIV are generally observed for wind speeds in the range of 1 to 7 m/s. The existing industrial practice for predicting how prone cables are to VIV fatigue is based on a balance between the power generated by the wind and the power dissipated by the cable system. The power generated by the wind has been evaluated through measurements on real line spans and through wind tunnel experiments on rigid and flexible cylinders as a function of frequency and vibration amplitude. The wind tunnel measurement results are mainly performed for constant flow speed. Corresponding results show a scattering from simple to double. Furthermore, complementary investigations are required to better evaluate the power with wind speed variations across and along the overhead line span. EDF R&D (with Code_Saturne open source software) and Politecnico di Milano have evaluated CFD modeling on a mobile rigid cylinder with comparison to detailed wind tunnel measurement results performed by Politecnico di Milano on a 20 cm diameter rigid cylinder equipped with a pressure scanner. This paper presents the steps, the different questions raised, the difficulties and limitations for the setting and the realization of the CFD modeling approach. The comparison between experimental results and simulation results is presented for the mobile rigid cylinder with k-ω SST turbulence model.

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Spray Drift from Dicamba and Glyphosate Applications in a Wind Tunnel

Weed Technology ◽

10.1017/wet.2017.15 ◽

2017 ◽

Vol 31 (3) ◽

pp. 387-395 ◽

Cited By ~ 11

Author(s):

Guilherme Sousa Alves ◽

Greg R. Kruger ◽

João Paulo A. R. da Cunha ◽

Bruno C. Vieira ◽

Ryan S. Henry ◽

...

Keyword(s):

Wind Speed ◽

Wind Tunnel ◽

Laser Diffraction ◽

Spray Drift ◽

Downwind Distance ◽

Fluorescent Tracer ◽

Drift Potential ◽

Herbicide Treatments ◽

Low Speed Wind Tunnel ◽

Nozzle Type

With the recent introductions of glyphosate- and dicamba-tolerant crops, such as soybean and cotton, there will be an increase in POST-applied tank-mixtures of these two herbicides. However, few studies have been conducted to evaluate drift from dicamba applications. This study aimed to evaluate the effects of dicamba with and without glyphosate sprayed through standard and air induction flat-fan nozzles on droplet spectrum and drift potential in a low-speed wind tunnel. Two standard (XR and TT) and two air induction (AIXR and TTI) 110015 nozzles were used. The applications were made at 276 kPa pressure in a 2.2 ms−1 wind speed. Herbicide treatments evaluated included dicamba alone at 560 gaeha−1 and dicamba+glyphosate at 560+1,260 gaeha−1. The droplet spectrum was measured using a laser diffraction system. Artificial targets were used as drift collectors, positioned in a wind tunnel from 2 to 12 m downwind from the nozzle. Drift potential was determined using a fluorescent tracer added to solutions, quantified by fluorimetry. Dicamba droplet spectrum and drift depended on the association between herbicide solution and nozzle type. Dicamba alone produced coarser droplets than dicamba+glyphosate when sprayed through air induction nozzles. Drift decreased exponentially as downwind distance increased and it was reduced using air induction nozzles for both herbicide solutions.

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