References of "De Cock, Nicolas"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailMeasurements of reference ISO nozzles by high-speed imaging
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Nuyttens, David et al

in Crop Protection (2016), 89

Agricultural spray characteristics determine the efficiency of a pesticide application because size and velocity affect droplet trajectory and impact behavior. At present, the relevance of different ... [more ▼]

Agricultural spray characteristics determine the efficiency of a pesticide application because size and velocity affect droplet trajectory and impact behavior. At present, the relevance of different characterization techniques remains controversial since discrepancies may be significant between measurements performed in different laboratories. A digital image acquisition technique and analysis algorithm is proposed for droplet size and velocimetry measurements as an alternative to well-established techniques such as the Phase Doppler Particle Analyzer (PDPA) or laser diffraction spectrometry (LDS). The algorithm requires double exposed shadow images acquired in a back-lighted arrangement with a Particle Image Velocimetry (PIV) camera and a pulsed light emitting diode (LED). Spatial illumination heterogeneities are corrected by subtracting from each image a mean background acquired on several images without any particle. The algorithm accuracy is ensured by the rejection of out-of-focus particles using a focus parameter depending on gradient intensity at the particle edges. Thresholds for focus particle selection were determined by studying the evolution of the focus parameter and the error on particle size measurements from images containing droplets with uniform size at various distance of the object plane. Selected droplets were identified on both pairs of images to determine their size and velocity. Droplet size distributions were corrected to account for the uneven sampling probability caused by the volumetric method. Droplet size distributions of a set of reference nozzle/pressure combinations defined in the ISO/DIS 25358 were measured. The image technique was able to distinguish each of the reference sprays well. Comparison with PDPA measurements showed that the imaging technique tends to measure an equivalent Dv50, a lower Dv10 and a higher Dv90 leading therefore to a higher relative span factor. Velocity measurements showed good agreement between both techniques except for one nozzle/pressure combination. [less ▲]

Detailed reference viewed: 21 (10 ULg)
Full Text
Peer Reviewed
See detailDynamics of a thin radial liquid flow
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Ouled Taleb Salah, Sofiene ULg et al

in Fire Safety Journal (2016), 83

The present work proposes an extension of the existing analytical development on the radial spread of a liquid jet over a horizontal surface to the case of a thin radial flow. When the gap, H, between the ... [more ▼]

The present work proposes an extension of the existing analytical development on the radial spread of a liquid jet over a horizontal surface to the case of a thin radial flow. When the gap, H, between the jet nozzle and the plate is reduced the discharging area may be smaller than the inlet area leading to an increase of the main flow velocity downstream of the thin cylindrical opening. This increase of velocity, de fined here as 1/alpha , can be related to the relative gap of the nozzle H/R with R the nozzle pipe radius. Numerical computations with a volume of fluid method were realised with for H/R ranging from 0.2 to 3 and with flow rates Q of 3 and 6 l/min1. The results of these computations allowed to express alpha in respect of H/R. Taking in account the flow acceleration allowed to extend the set of equation from the jet impacting flow to the thin cylindrical opening flow. The liquid layer thickness and the surface velocity diff er with a maximum error of 4% between the flow predicted by the model and computations. Main discrepancies appear in the region close to the nozzle where the analytical model assumption of a constant velocity outside the boundary layer is not valid. However, further downstream the model and the computations are in good agreement. [less ▲]

Detailed reference viewed: 21 (5 ULg)
Full Text
See detailReduced span spray – Part 1: Retention
Massinon, Mathieu ULg; De Cock, Nicolas ULg; Ouled Taleb Salah, Sofiene ULg et al

in Aspect of Applied Biology, International Advances in Pesticide Application (2016, January)

Maximising treatment efficiency for a given target lies mainly on depositing a maximum part of the spray volume within an optimal droplet size range, which has to be as narrow as possible to reduce ... [more ▼]

Maximising treatment efficiency for a given target lies mainly on depositing a maximum part of the spray volume within an optimal droplet size range, which has to be as narrow as possible to reduce retention variability and drift issues. The present work focuses on exploring the effect of span factor of the droplet size distribution on the final retention by a 3D target plant using a modelling approach with the final aim of guiding the development of a reduced span nozzle (Reduced span spray – Part 3: Design of narrow span nozzle). Five droplet size spans have been tested for three VMD and three wetting scenarios on the same 3D plant architecture. Performing a screening of the different parameters involved in spray retention with a modelling approach based on a deeper understanding of leaf/droplet interactions is a valuable approach for highlighting the optimal droplet size distribution maximising droplet retention for a given target/formulation combination. [less ▲]

Detailed reference viewed: 13 (1 ULg)
Full Text
See detailReduced span spray: Part 3: Design of a narrow span nozzle
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Ouled Taleb Salah, Sofiene ULg et al

in Aspect of Applied Biology (2016, January)

Optimisation of the droplet spectra of the agricultural spray may increase the spray application efficiency. The optimal spray would contain only the most efficient droplets in term of speed and size ... [more ▼]

Optimisation of the droplet spectra of the agricultural spray may increase the spray application efficiency. The optimal spray would contain only the most efficient droplets in term of speed and size. Therefore, this paper is presenting the first steps of the design of a narrow span nozzle in order to produce an optimised spray. The starting geometry is a splash plate nozzle with a disk ending with structures (i.e. tooth, grooves, and needles) that would separate the liquid sheet into jets. These jets would be in the Rayleigh regime which has the advantage of producing narrower droplet spectra than liquid sheet break-up. The present project aims to design a hydraulic nozzle producing a spray with a narrow drop size distribution in order to increase the agricultural spray application efficiency. In the present paper the first project steps are presented. [less ▲]

Detailed reference viewed: 26 (3 ULg)
Full Text
Peer Reviewed
See detailÉtude des potentialités des systèmes d’application contrôlée des gouttes (CDA) pour les traitements phytosanitaires en céréaliculture (synthèse bibliographique)
Ouled Taleb Salah, Sofiene ULg; De Cock, Nicolas ULg; Massinon, Mathieu ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment (2016)

Introduction. L’application contrôlée des gouttes (CDA) présente le double avantage de réduire à la fois l’étendue de la distribution des tailles des gouttes et le volume appliqué par rapport aux buses ... [more ▼]

Introduction. L’application contrôlée des gouttes (CDA) présente le double avantage de réduire à la fois l’étendue de la distribution des tailles des gouttes et le volume appliqué par rapport aux buses hydrauliques conventionnelles. Littérature. Cette revue investigue la potentialité de la CDA par rapport aux buses hydrauliques dans le cadre du désherbage précoce des adventices (2-3 feuilles). En termes de rétention, les études reliant les caractéristiques des gouttes (taille, vitesse et direction) et l’architecture, la densité et la mouillabilité du feuillage, en fonction de la formulation de bouillies, ont été abordées. Ces études montrent que des gouttes de 300 μm avec un adjuvant approprié et des jets émis 60° vers l’avant par rapport à la verticale contribuent à l’augmentation de la rétention sur les cibles problématiques à port dressé. L’effet des réductions des volumes d’application pour ces deux techniques est étudié sur base de la moyenne, du coefficient de variation et du taux de couverture des dépôts. Néanmoins, les résultats de ces études ne peuvent être généralisés du fait des différences de réglages opératoires entre les deux techniques d’application. Quant à la dérive, les atomiseurs CDA orientés horizontalement présentent un potentiel de dérive plus important que les buses hydrauliques pour lesquelles le spray est orienté vers le bas. La dérive augmente avec la vitesse du vent et diminue lorsque le diamètre médian volumétrique (DV50) augmente. Conclusions. De nouveaux réglages des atomiseurs de la CDA en termes de DV50 et de direction du jet peuvent répondre aux défis de l’agriculture de précision. Les pistes d’innovations proposées sont d’une part une amélioration de la résistance à l’usure des dents situées en bordure des disques et, d’autre part, une distribution granulométrique plus étroite. [less ▲]

Detailed reference viewed: 38 (8 ULg)
Full Text
See detailComputer simulations of spray retention by a 3D barley plant: effect of formulation surface tension
Massinon, Mathieu ULg; De Cock, Nicolas ULg; Ouled Taleb Salah, Sofiene ULg et al

in 67th International Symposium on Crop Protection (2015, May 19)

Detailed reference viewed: 38 (17 ULg)
Full Text
See detailDrop size distribution measurement of ISO nozzles by shadowgraphy method
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Ouled Taleb Salah, Sofiene ULg et al

in Drop size distribution measurement of ISO nozzles by shadowgraphy method (2015, May 19)

Detailed reference viewed: 46 (12 ULg)
Full Text
Peer Reviewed
See detailDrift potential of tilted shielded rotary atomisers based on wind tunnel measurements
Ouled Taleb Salah, Sofiene ULg; Massinon, Mathieu ULg; De Cock, Nicolas ULg et al

in 67th International Symposium on Crop Protection (2015, May 19)

Detailed reference viewed: 35 (6 ULg)
Full Text
Peer Reviewed
See detailDrift of tilted shielded rotary atomisers based on wind tunnel measurements
Ouled Taleb Salah, Sofiene ULg; Massinon, Mathieu ULg; De Cock, Nicolas ULg et al

in Proceedings of International Symposium on Crop Protection Ghent 2015 (2015)

Detailed reference viewed: 18 (2 ULg)
Full Text
Peer Reviewed
See detailStudy of retention variability on an early growth stage herbaceous plant using a 3D virtual spraying model
Massinon, Mathieu ULg; Dumont, Benjamin ULg; De Cock, Nicolas ULg et al

in Crop Protection (2015), 78

A model predicting the spray droplet interception and retention by a single virtual plant has been developed. The model was based on three main experimental inputs: the 3D architecture of a barley plant ... [more ▼]

A model predicting the spray droplet interception and retention by a single virtual plant has been developed. The model was based on three main experimental inputs: the 3D architecture of a barley plant, the spray quality and the droplet impact behavior. Two contrasted formulation scenarios, limits of the common range covered by pesticide application in terms of surface tension, were tested by changing the droplet behavior at impact in the model. Simulations were undertaken for studying the variability of spray retention resulting from spray quality, applied volume and plant size for a difficult-to-treat target. Results showed that the spray retention efficiency ranged from 6.8% to 96.6% of a theoretical full adhesion scenario, where all intercepted droplets were captured, according to spray quality for the two formulation scenarios tested. Average retention increased with increasing spray fineness, applied volume per hectare and plant size. Variability of deposits, evaluated using the coefficient of variation of simulated retentions, was found to be a function of the mean droplet density according to CV∝N^(-0.68), where CV is the coefficient of variation and N the number of droplet per square centimeter. Variability was also found to be a function of the plant size according to a relation CV∝S^(-0.5), where S is the total leaf area of the plant model. The variability of deposits increased with decreasing spray fineness, applied volume per hectare and plant size because of the reduced number of droplets contributing to retention. Wetting properties greatly influenced retention but surprisingly poorly influenced the variability of deposits. Such a modeling approach that is capable of an independent investigation of the influence of various parameters on spray retention can be used to improve understanding of application methods and adjuvants that could help minimizing development of resistance in problematic weed species. [less ▲]

Detailed reference viewed: 51 (21 ULg)
Full Text
See detailNumerical modelling of mirror nozzle flow
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Mercatoris, Benoît ULg et al

Conference (2014, July 15)

Detailed reference viewed: 92 (39 ULg)
Full Text
See detailEvaluation of process-driven spray retention model on ear-ly growth stage barley
Massinon, Mathieu ULg; Ouled Taleb Salah, Sofiene ULg; De Cock, Nicolas ULg et al

Conference (2014, July)

The efficiency of spray application of foliar plant protection products with hydraulic nozzles on vertically oriented and hydrophobic plants at early growth stages can be very low. The spray retention by ... [more ▼]

The efficiency of spray application of foliar plant protection products with hydraulic nozzles on vertically oriented and hydrophobic plants at early growth stages can be very low. The spray retention by crop leaves is affected by application parameters resulting from nozzle kind, size and operating pressure as well as spray mixture physicochemical properties. When optimizing the spray application, such targets are often used to perform retention trials for comparative purpose, i.e. indoor grown monocotyledonous at two leaves stage. A typical arrangement consists in spraying few plants sufficiently spaced underneath the nozzle to avoid interference due to secondary droplets from impacts on other plants. However, retention trials turn out to ineffective for significantly discriminating between application methods and mixtures due to the high variability between trials resulting from the different droplets retained by each plant. An alternative to retention trials is to tackle spray retention with a physical approach at the droplet scale. Such tests are often performed using high speed imaging with high magnification optics to characterize droplet impacts; adhesion, rebound or shatter on small excised leaf areas and neglect, however, the overall plant architecture. The aim of this paper is to evaluate a droplet interception model connecting actual spray retention with process-driven retention models. In this study, barley plants (BBCH11) were sprayed with 2 formulations using the same nozzle. The actual spray retention was assessed by dosing a fluorescent tracer added to the sprayed mixture. The plants were placed linearly below the center of a single moving nozzle during sprayings. Each plant was reconstructed in 3D afterwards using a structured light 3D scanner and used as input for the model. A virtual nozzle was built on the base of droplet size distributions measured with high speed shadow imaging by performing an adjustment of the distribution by the method of moments. A ran-dom droplet distribution was allocated for each spraying of a barley plant. Droplet velocities were given to droplets on the basis of the droplet velocity – diameter correlation by resolving the droplet transport equations for different droplet sizes. Initial droplet positions were ran-domly given. The interception model is based on a mathematical formalism for the intercep-tion between triangles of the 3D plant and droplet directions. If the droplet impacts a leaf, the amount actually retained by the leaf was computed on the basis of the droplet impact energy and impact behavior from experiments with high speed shadow imaging. In conclusion, the interception model allowed determining the spray retention by plants and discriminating ap-plication parameters by explaining the variability resulting from various droplet size distribu-tions intercepted by single plant. [less ▲]

Detailed reference viewed: 95 (35 ULg)
Full Text
See detailAgricultural spray measurement by high-speed shadow imagery
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Scientific conference (2014, January 10)

Spray characteristics determine treatment performance and environmental contamination. Shadowgraphy associated with high-speed imaging presents an attractive option for measuring drop velocity and size ... [more ▼]

Spray characteristics determine treatment performance and environmental contamination. Shadowgraphy associated with high-speed imaging presents an attractive option for measuring drop velocity and size simultaneously. This study presents an overview of the contrast problems occurring when using backlighted images and proposes appropriate solutions for reliable and quality measurements. Drop diameter measurement is based on the area inside the sub-pixel contour assuming a circular shape. Drop velocity is determined by tracking a drop on two successive images taking into account the drop size, speed limits and the general flow direction. Then, the drop size distribution is corrected taking in account the sampling rate of each drop. Finally, a comparison between PDA and shadowgraphy measurements realized simultaneously on the same spray location is presented. [less ▲]

Detailed reference viewed: 128 (41 ULg)
Full Text
See detailCHARACTERIZATION OF AGRICULTURAL SPRAY BY DIGITAL ANALYSIS OF SHADOWGRAPHY IMAGES
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2013, February 08)

Agricultural sprays are among the most common two-phase flows studied because their characteristics determine the efficiency of treatment as well as environmental contamination. At present, the relevance ... [more ▼]

Agricultural sprays are among the most common two-phase flows studied because their characteristics determine the efficiency of treatment as well as environmental contamination. At present, the relevance of different characterization techniques of the highly polydispersed sprays used in this application remains controversial. Digital analysis of shadowgraphy images presents an attractive option for the characterization of both velocity and size of droplets present in the spray. This study presents an overview of the contrast problems inherent in the use of backlighted images and propose appropriate solution to ensure the quality of measurements. Generally, background light presents heterogeneities associated with light sources and optical arrangement. These can be solved by substracting from each images a composite background. An other particular focus is given to one major drawback of volumetric lighting, the presence of out focus droplets. These droplets have to be removed during the image analysis process because the measurement of their diameters can't be done accuratly. The rejection of these out of focus objects is based on a quantitative parameter which was calibrated with a obliquely shot monodispersed spray. The final step of the image processing is determining velocity of the droplet by tracking a same droplet on two successive images. The tracking algorithm is based on the size of the droplet, its more probable displacement and its direction. [less ▲]

Detailed reference viewed: 39 (12 ULg)
Full Text
See detailCaractérisation de jets agricoles par traitement d'images
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Software (2013)

A digital image analysis algorithm is proposed as an alternative to established optical techniques such as Phase Doppler Particle Analyser (PDPA) or laser diffraction spectrometry (LDS) for the ... [more ▼]

A digital image analysis algorithm is proposed as an alternative to established optical techniques such as Phase Doppler Particle Analyser (PDPA) or laser diffraction spectrometry (LDS) for the experimental determination of the size and velocity distributions of droplets produced by agricultural nozzles . The algorithm requires pairs of grayscale images acquired within a very short time for particle tracking in a backlighted arrangement. Spatial illumination heterogeneities are corrected by subtracting a mean background from each image. Droplets are then localized and sized. The algorithm accuracy is ensured by the rejection of out of focus particle using a focus parameter depending on gradient intensity at particle edges. Thresholds for in-focus particle selection were determined by studying the evolution of the focus parameter and the error on particle size measurement from images containing known size droplets at various distance of the object plane. Selected droplets are identified on both images of the pair for determining their velocities. Finally, drop size distribution is corrected to account for the uneven sampling probability caused by the volumetric method. [less ▲]

Detailed reference viewed: 110 (35 ULg)
Full Text
See detailImagerie par ombroscopieavec eclairage LED
De Cock, Nicolas ULg; Lebeau, Frédéric ULg

Scientific conference (2012, June 07)

Imagerie par ombroscopie avec LEDs pulsées L’imagerie par ombroscopie est une technique adaptée à la visualisation des gouttes, particules, bulles,.. Cette méthode se base sur une imagerie de haute ... [more ▼]

Imagerie par ombroscopie avec LEDs pulsées L’imagerie par ombroscopie est une technique adaptée à la visualisation des gouttes, particules, bulles,.. Cette méthode se base sur une imagerie de haute résolution et un éclairage de fond pulsé. Dans une variante de la méthode, la lumière est émise au moyen de sources LEDs de haute puissance focalisées par des optiques en vue d'obtenir une haute illumination de la scène. Le plan focal et la profondeur de champ des composants de l’optique définissent le volume de mesure en combinaison avec le filtrage de l'image réalisé en post-traitement. Ce post-traitement s'impose pour régler les problèmes d'uniformité de l'arrière plan provenant tant des différences entre LEDs que des particules non focalisées ainsi que de différences d’atténuation en fonction de la taille des particules. La source lumineuse est une lampe composée de LEDs pulsées à un intervalle fonction de la vitesse des particules. En utilisant une impulsion courte pour l’éclairage et un overdrive du courant nominal des LEDs, il est possible de figer le mouvement jusqu’à des vitesses élevées par des temps d'exposition de quelques microsecondes. Un contrôleur à deux voies permet de réaliser une double impulsion, ce qui combiné à une caméra double exposition permet la détermination des vitesses de particules en fonction de leur taille. Des travaux sur la mesure de granulométrie et vitesse de jet en pulvérisation agricole ainsi que d'impact de gouttes sur des surfaces superhydrophobes illustent le propos. Une technique de calibrage des algorithmes au moyen de gouttes monodisperses est présentée. [less ▲]

Detailed reference viewed: 56 (12 ULg)