References of "Lebeau, Frédéric"
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See detailA low-cost, multiplexable, automated flow cytometry procedure for the characterization of microbial stress dynamics in bioreactors
Brognaux, Alison ULg; Han, Shanshan; Sorensen, Soren J et al

in Microbial Cell Factories (2013), 12(100), 1-14

Background Microbial cell population heterogeneity is now recognized as a major source of issues in the development and optimization of bioprocesses. Even if single cell technologies are available for the ... [more ▼]

Background Microbial cell population heterogeneity is now recognized as a major source of issues in the development and optimization of bioprocesses. Even if single cell technologies are available for the study of microbial population heterogeneity, only a few of these methods are available in order to study the dynamics of segregation directly in bioreactors. In this context, specific interfaces have been developed in order to connect a flow cytometer directly to a bioreactor for automated analyses. In this work, we propose a simplified version of such an interface and demonstrate its usefulness for multiplexed experiments.Results A low-cost automated flow cytometer has been used in order to monitor the synthesis of a destabilized Green Fluorescent Protein (GFP) under the regulation of the fis promoter and propidium iodide (PI) uptake. The results obtained showed that the dynamics of GFP synthesis are complex and can be attributed to a complex set of biological parameters, i.e. on the one hand the release of protein into the extracellular medium and its uptake modifying the activity of the fis promoter, and on the other hand the stability of the GFP molecule itself, which can be attributed to the protease content and energy status of the cells. In this respect, multiplexed experiments have shown a correlation between heat shock and ATP content and the stability of the reporter molecule. Conclusion This work demonstrates that a simplified version of on-line FC can be used at the process level or in a multiplexed version to investigate the dynamics of complex physiological mechanisms. In this respect, the determination of new on-line parameters derived from automated FC is of primary importance in order to fully integrate the power of FC in dedicated feedback control loops. [less ▲]

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See detailReview of physicochemical processes involved in agrochemical spray retention
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013)

This review provides a broad view of the processes and parameters involved in applying agrochemicals to the leaves of field crops. Treatment efficiency is assessed using macroscopic and microscopic ... [more ▼]

This review provides a broad view of the processes and parameters involved in applying agrochemicals to the leaves of field crops. Treatment efficiency is assessed using macroscopic and microscopic approaches to investigate spray retention. With the macroscopic approach, aspects related to spray coarseness, carrier volume, leaf wettability, plant architecture, crop density and additives are addressed. Comparative studies have highlighted the wide variability in spray retention as a function of these parameters. They have failed, however, to describe the underlying physical relationships clearly enough to generalize the results. These relationships are better investigated using a microscopic approach, where drop impact behavior is established in relation to target surface and fluid properties. The wetting regime (either Wenzel or Cassie-Baxter) depends on the leaf surface microscopic roughness ratio (r) and chemical nature, fluid dynamic surface tension and drop impact energy. Adhesion, rebound and disintegration have been observed successively with increasing drop impact energy. Transitions between impact outcomes are influenced by fluid rheology and the dynamic surface tension of the fluid. The effect of surface orientation remains poorly explored, but it seems to have a limited influence on retention. Recent fundamental studies on superhydrophobicity and wetting should help practitioners in their search for an ever more rational application of agrochemicals. They could also drive the development of new systematic retention testing methods. [less ▲]

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See detailAssessment of pesticide application method efficiency by high-speed image analysis
Massinon, Mathieu ULg; Denis, Thierry; Perriot, Benjamin et al

Conference (2012, July 08)

This paper investigates if increased blackgrass weeding efficiency by reduced volume per hectare observed during 2010 Arvalis field trials may be related to increased pesticide application method ... [more ▼]

This paper investigates if increased blackgrass weeding efficiency by reduced volume per hectare observed during 2010 Arvalis field trials may be related to increased pesticide application method efficiency. Retention on blackgrass leaves was assessed by an image analysis method. The setup consists of a high-speed camera shooting drop impact on horizontal leaf target. An herbicide (Archipel® [125 g/ha] + Actirob® [1 l/ha]) was sprayed at the usual volume of 150 l/ha and at a reduced volume of 65 l/ha. Adjuvants use (Epsotop® [1%] + Heliosol® [0.5%]) was also evaluated at 65 l/ha to highlight the effect of mixture surface tension modification. Drop properties before impact were extracted by image analysis and a phase diagram derived. Volumetric proportions of impact types are determined inside 11 energy classes to assess the effect of formulation and application method. The volume median diameter (VMD) before impact was slightly decreased by the reduction to 65 l/ha because of nozzle and pressure changes and also by the use of the adjuvants leading to the reduction of surface tension. Without adjuvants the reduction to 65l/ha increased the proportion of adhesion while rebound remained unchanged and fragmentation decreased. With adjuvants, drop fragmentation occurs for a lower energy class but the proportion of fragmentation also decreases with because of reduced VMD. A slight effect on the transitions between impact classes was observed because of formulation concentration change at reduced volume/hectare. A major effect of adjuvants on retention was highlighted as bouncing disappeared. [less ▲]

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See detailTHE EFFECT OF LEAF ORIENTATION ON SPRAY RETENTION ON BLACKGRASS
Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg; MARECHAL, Pierre- et al

Conference (2012, July)

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop ... [more ▼]

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop trajectory and the variability of the leaf orientation. As the effect of impact angle on retention is still poorly documented, laboratory studies were conducted to highlight the effect of leaf orientation on drop impact outcomes. Measurements were performed with a high-speed camera coupled with a retro-LED lighting. Size and velocity of the drop were extracted by image analysis. Drop impact types were determined by the operator. Drops were produced with a flat-fan nozzle mounted on a movable ramp. Excised blackgrass [Alopecurus myosuroides HUDS. (ALOMY)] leaves were stretched between two parts of a U-shaped support. A surfactant (Break-Thru® S240) was sprayed to highlight the effect of mixture surface tension. The whole device was tilted from 0 to 90°. Relative volume proportions were computed within of an energy scale divided into 11 classes. These proportions have been weighted by an average volume distribution and the results were summed for all energy classes to obtain the total volume proportions for each impact outcomes and for all leaf angles. For distilled water (high surface tension) the increase of rebound proportion with the increase of drop impact angle is highlighted. For surfactant (lower surface tension), it results in an increase of drop fragmentation in Cassie-Baxter wetting regime. To be statistically representative, bigger drop samples should be used. [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 ▲]

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See detailExperimental method for the assessment of agricultural spray retention based on high-speed imaging of drop impact on a synthetic superhydrophobic surface
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in Biosystems Engineering (2012), 112(1), 56-64

Spray retention is a critical stage in pesticide application since non-retained drops can result in reduced efficacy, economic loss and environmental contamination. Current methods of retention assessment ... [more ▼]

Spray retention is a critical stage in pesticide application since non-retained drops can result in reduced efficacy, economic loss and environmental contamination. Current methods of retention assessment are based either on field experiments or laboratory studies. The former are usually performed on whole plants under realistic spray application conditions but offer no insight into the physics behind the process whilst the latter mainly focus on drop impact physics but are usually restricted to unrealistically low drop speeds. The aim of the paper is to devise an experimental method to investigate retention at drop scale level as a function of operational parameters but under controlled realistic conditions. A device based on highspeed video was developed to study retention on a synthetic superhydrophobic surface for a moving agricultural nozzle. The sizes and velocities of the drops generated were measured immediately before impact using image analysis. Impact class proportions were established and transition boundaries between impact outcomes were quantified using Weber number. Two contrasting experiments were performed to investigate the ability of method to detect small parametric changes. The insignificant changes in spray pattern that occur from pressure changes, did not significantly affect impact class boundaries, but changed the proportion of drops in each class because of size and velocity variations. The use of a surfactant reduced the volume median diameter of the spray, increased impact speed and changed the impact class boundaries. The method should allow a precise parametric investigation of spray retention in laboratory and close to field conditions. [less ▲]

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See detailStudy of pesticide retention on leaves using high-speed imaging
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2012, February 08)

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See detailComparison of spray retention on synthetic superhydrophobic surface with retention on outdoor grown wheat leaves
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in International Advances in Pesticide Application: Aspects of Applied Biology 114, 2012 (2012, January)

A method has been designed to test the retention of drops generated by a moving agricultural nozzle using high speed imaging both on synthetic and leaf surfaces. The method allows a precise investigation ... [more ▼]

A method has been designed to test the retention of drops generated by a moving agricultural nozzle using high speed imaging both on synthetic and leaf surfaces. The method allows a precise investigation of spray retention by a characterisation of impact speed, drop diameter and impact behaviour. The paper presents a comparison of the spray behaviour on the synthetic surface with the behaviour on outdoor grown wheat leaves fixed on a microscope slide. Target surfaces were horizontal. A range of surface tension was tested using the tank-mix adjuvant Break-Thru S240 at different concentrations in distilled water. Results show the relevance of a synthetic surface for use as reference for the assessment of spray application efficiency. The drop behaviour on the superhydrophobic slide was representative of difficult-to-wet leaves surfaces. The reference surface avoids the natural variability of leaves and is therefore more suited to conduct comparative assessment of formulation retention performance. [less ▲]

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See detailÉvaporation d’une gouttelette en chute libre dans l’air
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Software (2012)

Simple model taking into account the movement and transfer of heat and mass at the droplet in free fall in the air.

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See detailHygrothermal modelling of Lime-Hemp concrete used as building material and indoor climate buffering characterization
Dubois, Samuel ULg; Evrard, Arnaud; Lebeau, Frédéric ULg

Poster (2012)

Hygroscopic building materials can affect the indoor air by exchanging moisture with it and buffering the ambient humidity variations. The Nordtest protocol and the concomitant Moisture Buffer Value (MBV ... [more ▼]

Hygroscopic building materials can affect the indoor air by exchanging moisture with it and buffering the ambient humidity variations. The Nordtest protocol and the concomitant Moisture Buffer Value (MBV) parameter definition has been one of the first attempt to characterize this moisture regulation performance. This paper present an attempt to confront this well-established experimental protocol with a mathematical model implemented in the Comsol multiphysics solver. The power of the simulation will be showed with a good correlation between the modelling and the experimental phase for the MBV determination of a lime-hemp concrete bloc. [less ▲]

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See detailÉtude de la distribution granulométrique de particules de chanvre: Méthodes par tamisage et analyse d'image
Dubois, Samuel ULg; Lebeau, Frédéric ULg

Report (2011)

Ce document présente une analyse de la répartition granulométrique d'une chènevotte commerciale. Deux techniques différentes sont étudiées. La première consiste à séparer les particules mécaniquement par ... [more ▼]

Ce document présente une analyse de la répartition granulométrique d'une chènevotte commerciale. Deux techniques différentes sont étudiées. La première consiste à séparer les particules mécaniquement par tamisage. La diversité morphologique des particules de chanvre entraîne cependant des questions quant à l'interprétation des résultats obtenus, et plus particulièrement sur les paramètres physiques réellement discriminatoires dans cette séparation en classes granulométriques. Il est montré ici que l'analyse d'image permet de répondre à cette question et d'apporter des informations précieuses dans la description des particules. A cette fin, la performance de descripteurs issus d'algorithmes de calcul en analyse d'image est étudiée. Enfin, une représentation multi-classes de la distribution granulométrique de la chènevotte est proposée, regroupant les descriptions dimensionnelle et morphologique des particules. [less ▲]

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See detailRTDrift, modèle permettant d’évaluer en temps réel les risques environnementaux liés à la dérive des produits phytosanitaires
Lebeau, Frédéric ULg; Massinon, Mathieu ULg; Verstraete, Arnaud et al

Conference (2011, October 17)

Un modèle, RTDrift, a été développé pour estimer la contamination causée par la dérive pour les pulvérisateurs à rampe en cours de traitement. Un pulvérisateur a été équipé de capteurs pour mesurer les ... [more ▼]

Un modèle, RTDrift, a été développé pour estimer la contamination causée par la dérive pour les pulvérisateurs à rampe en cours de traitement. Un pulvérisateur a été équipé de capteurs pour mesurer les paramètres de la dérive dont la pression de pulvérisation, les mouvements de rampe, la vitesse et direction du vent, la température et l’humidité ainsi que la géo-localisation. Pour chaque position successive des buses, un modèle de diffusionadvection gaussien avec sédimentation est utilisé pour calculer à partir de la buse le transport de chaque classe de gouttes déterminée préalablement par granulométrie laser en prenant en compte l’évaporation. Différents essais de terrain ont été réalisés où la dérive a été mesurée à différentes distances par fluorométrie sur collecteurs. La comparaison avec le modèle montre une estimation satisfaisante de la dérive sur base des mesures embarquées et offre le potentiel d’un estimateur de dérive en temps réel. Les pistes d’améliorations ultérieures sont évoquées. [less ▲]

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See detailA FEASIBILITY STUDY OF DEVELOPING DIRECT INJECTION SPRAYING TECHNOLOGY FOR SMALL SCALE FARMS
El Aissaoui, Abdellah ULg; Lebeau, Frédéric ULg; el bahir, Lhoussein et al

in SZABÓ, Istvan; MAGÓ, László; KURJÁK, Zoltán (Eds.) II. INTERNATIONAL CONFERENCE OF THE CIGR HUNGARIAN NATIONAL COMMITTEE, THE FACULTY OF MECHANICAL ENGINEERING OF THE SZENT ISTVÁN UNIVERSITY, AND THE AGRICULTURAL ENGINEERING BOARD OF THE HUNGARIAN ACADEMY OF SCIENCES (2011, October 12)

The present study focuses on designing hydraulic scheme and process control system for small direct injection sprayer equipped with five meters' boom (10 tip nozzles) based on DC electrical energy supply ... [more ▼]

The present study focuses on designing hydraulic scheme and process control system for small direct injection sprayer equipped with five meters' boom (10 tip nozzles) based on DC electrical energy supply. A numerical model was developed by using finite volume method to study dynamic of concentration change process and to optimize the hydraulic boom design required to overcome lag transport problem related to real time application. The schemes of serial and parallel boom layouts were studied to obtain minimal lag transport for chemical concentration change process. The process control system was modelled in Matlab-SimulinkTM, and a laboratory test bench was implemented with a PID (Proportional Integral Derivative) feedback control for evaluating the performance of the constant carrier flow and the variable total flow strategies. The results of the hydraulic modelling of the serial boom layout showed that 6 mm boom diameter gave a satisfying performance in term of application uniformity (up to 97%) and lag transport along nozzles (from 0.8 to 1.5 s). The prospection of parallel scheme by feeding individually nozzles gave an even reduced lag transport (2 s) along the boom (diameter of 4 mm). The modelling of constant carrier flow control strategy showed a lag time of 2.5 s for the step speed change of 0.6 to 1.2 m/s at constant pressure of 2 bars. The total flow control strategy showed the advantage of reducing lag transport from 4 to 2.3 s when speed varied from 0.6 to 1.2 m/s in accordance with operating pressure (from 1 to 3 bars). The experimental tests showed the importance of varying carrier flow rate to improve the controller dynamic in comparison to the constant carrier flow control. [less ▲]

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See detailRTDrift: a real time model for estimating spray drift from ground applications
Lebeau, Frédéric ULg; Verstraete, Arnaud ULg; Stainier, Charles ULg et al

in Computers & Electronics in Agriculture (2011), 77(2), 161-174

A spray drift model called RTDrift was developed to estimate drift caused by ground sprayer machines. The sprayer was equipped with sensors measuring operational parameters namely spray pressure, boom ... [more ▼]

A spray drift model called RTDrift was developed to estimate drift caused by ground sprayer machines. The sprayer was equipped with sensors measuring operational parameters namely spray pressure, boom height and movements, and geolocalization. Climatic parameters, including wind speed and direction, were measured using a 2-D ultrasonic anemometer mounted on the sprayer. The nozzles spray drop size spectra were characterized using Phase Doppler Interferometer measurements. At every successive boom position, a diffusion-advection Gaussian tilted plume model computed the spray drift deposits for each drop class taking into account evaporation. The contribution of a single nozzle was calculated by integration of the individual puffs with respect to time and summation of the contributions of individual drops classes. The overall drift generated by the sprayer machine was obtained adding the contributions of all the nozzles. Field trials were performed on a fallow field with water and on crops with pesticides in various wind conditions. The ground drift was measured at different drift distances using fluorometric methods. When comparing the results of the model with experimental measurements of deposits, the model produced realistic maps of drift deposits. Some further improvement is needed in the presence of large scale eddies. The model offers potential benefits for the farmer as a real time drift estimator embedded on a sprayer machine [less ▲]

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See detailDevelopment of process control system for potential use of direct injection spraying technology
Aissaoui, Abdellah; Lebeau, Frédéric ULg; el bahir, et al

in Progress in Agricultural Engineering Sciences (2011), 7(1), 33-45

Small-scale farmers face to actual difficulties of applying pesticides accurately and safely on vegetables crops. They mainly use hand operated sprayers. As an issue, a small direct injection system based ... [more ▼]

Small-scale farmers face to actual difficulties of applying pesticides accurately and safely on vegetables crops. They mainly use hand operated sprayers. As an issue, a small direct injection system based on a five meter’s parallel boom layout was designed to improve chemical application. The boom layout was optimized to obtain the same minimal time lag response for the ten nozzles. The dynamic of the system was modeled using Simulink TM as first order model with delay. Two control strategies were implemented using PID (Proportional Integral Derivative) feedback control loops to monitor tracer injection (fluorescing) proportionally to simulated forward speed (from 0.6 to 1.2 m/s) and to control the constant operating pressure (constant carrier flow strategy) or the variable operating pressure proportionally to the injected chemical amount (variable total flow strategy). Different forward speed changes were induced using steps up and down, ramps, sine waves and sweeps excitations to evaluate the control feedback. The system stability was tested for its ability to maintain the expected concentration and application rate. The results show that the time lag remains less than 3 s (dead time < 2 s, time constant < 1 s) and the system keeps stable for the maximal speed variation (ΔV) and acceleration (ā) tested (ΔV = 200%, ā = 0.48 m/s2) which induce less than 10% variation of application rate. [less ▲]

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See detailREAL-TIME MONITORING OF ENVIRONMENTAL FACTORS TO MODEL WHEAT YIELD PRODUCTION
Dumont, Benjamin ULg; Leemans, Vincent ULg; Lebeau, Frédéric ULg et al

Poster (2010, September 07)

This paper presents the results of a one year preliminary study in which a real-time monitoring system was used to feed the STICS soil crop model. The monitoring system was made of a self-organising ... [more ▼]

This paper presents the results of a one year preliminary study in which a real-time monitoring system was used to feed the STICS soil crop model. The monitoring system was made of a self-organising wireless network within which microsensors collected and stored microclimatic and environmental data. As indicated by the statistical criteria (RMSE, normalized deviation and model efficiency), the optimisation of some wheat crop parameters allows the STICS model to predict the yields with good accuracy for three different soil types and seven different nitrogen application rates. [less ▲]

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See detailA MODEL FOR WHEAT YIELD PREDICTION BASED ON REAL-TIME MONITORING OF ENVIRONMENTAL FACTORS
Dumont, Benjamin ULg; Lebeau, Frédéric ULg; Vancutsem, Françoise ULg et al

Poster (2010, July)

This paper presents the results of a one year preliminary study in which a real time monitoring system was used to feed the STICS soil crop model. As indicated by the statistical criteria (RMSE and model ... [more ▼]

This paper presents the results of a one year preliminary study in which a real time monitoring system was used to feed the STICS soil crop model. As indicated by the statistical criteria (RMSE and model efficiency), the optimization of some wheat crop parameters allows the model to predict the yields with good accuracy for different soil type and different nitrogen application rates. [less ▲]

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See detailTEST AND EVALUATION OF TWO PROCESS CONTROL STRATEGIES FOR ADAPTING DIRECT INJECTION PESTICIDE APPLICATION TO SMALL SCALE FARMS
El Aissaoui, Abdellah ULg; Lebeau, Frédéric ULg; Destain, Marie-France ULg et al

Conference (2010, January 13)

Small scale farmers, in developing and in some developed countries, are faced to actual difficulties of applying pesticides accurately and safely on vegetables crops. They mainly use hand operated ... [more ▼]

Small scale farmers, in developing and in some developed countries, are faced to actual difficulties of applying pesticides accurately and safely on vegetables crops. They mainly use hand operated sprayers. As an issue, a small direct injection system based on a five meter's parallel boom layout was designed to improve chemical application. The boom layout was optimised to obtain the same minimal lag time response for the ten nozzles. The dynamic of the system was modelled using SimulinkTM as first order model with delay. Two control strategies were implemented using PID feedback control loops to monitor tracer injection (fluorescing) proportionally to simulated forward speed (from 0.6 to 1.2 m/s) and to control the constant operating pressure (constant carrier flow strategy) or the variable operating pressure proportionally to the injected chemical amount (variable total flow strategy). Different forward speed changes were induced using steps up and down, ramps, sine waves and sweeps solicitations to evaluate the control feedback. The system stability was tested for its ability to maintain the expected concentration and application rate. The results show that the lag time remains less than 3 s (dead time < 2s , time constant < 1s) and the system keeps stable for the maximal speed variation and acceleration tested (∆V=200%, a= 0.48 m/s2) which induce less than 10% variation of application rate. [less ▲]

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See detailDroplet internal flow measurement using micro-PIV
Lebeau, Frédéric ULg; Vetrano, Maria-Rosaria; van Beeck, Jeroen et al

Poster (2009, September 25)

The micro-PIV technique represents a development of the general particle image velocimetry technique to applications in fluid mechanics phenomena at a micrometric scale. It takes advantage from the very ... [more ▼]

The micro-PIV technique represents a development of the general particle image velocimetry technique to applications in fluid mechanics phenomena at a micrometric scale. It takes advantage from the very small depth of field of long distance objectives with high magnification to carry out accurate measurements in the focusing plane. The typical configuration consists of a microscope coupled to a pulsated laser and a double exposure PIV camera. The flow is seeded using sub-micrometric fluorescent particles. The laser light is directed on the investigated flow through the epifluorescent microscope objective. The light re-emitted by the fluorescent particles is detected by the PIV camera equipped of an optical filter to select only the fluorescence wavelength. The micro-PIV technique presents a large interest in the validation of numerical codes developed in different micro-fluidic framework such as biological flows and in industrial application as the ink-jet print-head. To investigate the micro-PIV measurements capabilities for fast moving and deforming droplets, measurement of the flow inside a jet ejected by a piezo-driven capillary up to the droplet formation by Rayleigh instability are studied in combination with PTV in order to distinguish the main liquid movement from the bulk one. Liquids differing from each other for their viscosity and their surface tension as well as piezo-element frequency in the 1 to 8 KHz range are investigated. The flow rate of the jet is adjusted by means of a pushing syringe system. Low concentration of 0.86 microns fluorescent particles is employed as seeding in order to have good signal to noise ratios. The ensemble averaging method is used to increase the height of the correlation peaks. Stroboscopic method is used to achieve several couples of frames taken in the same conditions thanks to high repeatability of piezo-driven instabilities. Moreover changing the delay of stroboscopy all the droplet formation phases can be analyzed in detail. In the experimental configuration, optical aberrations play a role since they affect the position and shape of the particle images and as a consequence the velocity field. The two main optical aberration experienced are astigmatism and measurement plane deformation. Astigmatism cannot be avoided in the experimental configuration, as it is clearly observed on droplet images were particles above and bellow the focalisation plane appear as perpendicular lines (Fig 1a). Nevertheless cross correlation method is not sensitive on particle image shape. As the measurement plane defined by the focal plane of the microscope is located inside a curved transparent object, it deformed as it was passing through a lens. The deformation of the objective plane affects the measurements as a function of the optical configuration, droplet curvature and relative refractive index. However, in the studied configuration, deformed plane differs only from the straight one of about 8 µm. The micro-PIV method is therefore suited to measure the instantaneous vector field inside droplets through cross-correlation methods (Fig 1b). The internal flow recirculation is observed. Measurements can be also performed in different planes inside the droplet depending on focalisation plane. [less ▲]

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See detailApplying control volume finite element for modelling direct injection boom spraying flow
El Aissaoui, Abdellah; Lebeau, Frédéric ULg; Destain, Marie-France ULg et al

Conference (2009, June 23)

Assessment of injection lag transport and uniformity of direct injection boom sprayer is an important issue for successful variable rate spraying technology. To estimate the boom lag transport and ... [more ▼]

Assessment of injection lag transport and uniformity of direct injection boom sprayer is an important issue for successful variable rate spraying technology. To estimate the boom lag transport and pressure loss, a numerical model is formulated on the basis of fluid hydrodynamic conservation equations. The software is implemented in visual basic. To solve the pressure – velocities equations, control volume finite element method (CV) is used to delimit elementary volumes of the boom. Linearization of the conservation laws is ensured by considering discrete form of the equations and calculating velocity and pressure step by step throughout the whole boom. The flow behaviour is simulated into a boom section divided into N elementary volumes, each of them including one nozzle. To test the model, three boom diameters (5, 6 and 8 mm) and two chemical viscosities (10-6 and 10-5 m2/s) were used. Experimental trials are carried out on boom having 2.5 m length (5 nozzles) for measuring pressure gradient and lag transport. Results showed that the model can predict the pressure losses and the lag transport accurately (error within 5%) to optimize boom designs. [less ▲]

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