References of "De Cock, Nicolas"
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See detailNumerical modelling of mirror nozzle flow
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Mercatoris, Benoît ULg et al

Conference (2014, July 15)

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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 ▲]

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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 ▲]

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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 ▲]

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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: 44 (12 ULg)