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Determining the viscous splash losses in the housing of a hydraulic motor through CFD-simulations : A master thesis in collaboration with Bosch-Rexroth in Mellansel ABLarsson, Tommy January 2017 (has links)
One possible way of solving future energy shortages is by the optimization of our current energy consumption. These optimizations must span all possible fields of consumption. In the mechanical field radial piston hydraulic motors may show some margin of improvement. The radial piston hydraulic motor is driven by a pressure difference in hydraulic oil. These motors are commonly found in heavy industrial equipments such as drills and conveyor belts. The advantage with these motors in comparison with electric motors is the high torque and ability to absorb shock loads that may cause damage to electrical motors. The effectiveness of these motors are determined both by the motor and by the drive system as a whole consisting of hydraulic pump driven by a electric motor, hydraulic hoses, motor and possible external coolers. If the effectiveness of the motor is low the whole drive system will be affected thus amplifying the total losses. The losses in the motor can be both mechanical and derived to the viscosity of the oil. One region in the motor where there are viscous losses are in the housing. The housing is filled with oil, that both aids in the cooling and acts as a lubricant for the motor. Pistons and rollers are some of the components found in the housing. These components rotates around the centre line axis while having a pulsating radial motion following a cam ring. This rotating and pulsating motion will push oil in and out of a volume between two consecutive pistons and rollers. This will create viscous losses and regions with a enhanced risk of cavitation. This study investigates if the flow of oil in the housing can be simulated accurately. The study also examine what are the main problems regarding the flow of oil in the housing and the factors affecting the size of the viscous losses. The study also examines the correlation between viscosity and viscous losses. Finally two different optimizations with the intention of decreasing the viscous losses are compared. The study found that the majority of the viscous losses in the housing can be derived to the flow of hydraulic oil in and out of the volume between two consecutive pistons and rollers. The oil will pass a sharp edge around the cylinder block and a narrow passage under the spacing between the cylinder rows in a two cam ring configured motor. This will create regions with a enhanced velocity and risk of cavitation. The stroke of the motor will greatly affect the effectiveness of the motor especially at a high rotational speed. The viscous losses will be transformed into internal energy, heat, thus increasing the temperature of the oil. A increased temperature will decrease the viscosity and the viscous losses. The viscous losses will vary with 17 % if the viscosity is varied between 20 and 100 cSt. The developed model is not sufficient to determine the viscous losses accurately since the geometry had to be considerably simplified, but can act as a way of comparing different optimizations of the motor. The viscous losses can be decreased with 25 % in the CCe motor at 150 rpm by milling material of the cylinder block between the piston holes. This is an expensive optimization and needs to be justified from a cost-benefit perspective.
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Analysis of a Goldschmied Propulsor Using Computational Fluid Dynamics Referencing California Polytechnic's Goldschmied Propulsor TestingSeubert, Cory A 01 September 2012 (has links) (PDF)
The Goldschmied Propulsor is a concept that was introduced in mid 1950's by Fabio Goldschmied. The concept combines boundary layer suction and boundary layer ingestion technologies to reduce drag and increase propulsor efficiency. The most recent testing, done in 1982, left questions concerning the validity of the results. To answer these questions a 38.5in Goldschmied Propulsor was constructed and tested in Cal Poly's 3x4ft wind tunnel. The focus of their wind tunnel investigation was to replicate Goldschmied's original testing and increase the knowledge base on the subject. The goal of this research was to create a computational fluid dynamics (CFD) model to help visualize the flow phenomenon and see how well CFD was able to replicate Cal Poly’s wind tunnel results. CFD cases were run to get a comparison of the computational model and the wind tunnel results. For the straight tunnel geometry for the 0.385” slot and cusp A we found a body, pressure and friction drag, fan off CD of 0.0526 and a fan on at 500 Pascals with a CD of 0.0545. This is similar to the wind tunnel results but because of large errors in measuring overall drag we are not able to directly compare to the wind tunnel results. Overall we see that the trends match, mainly that the fan does not decrease the total pressure drag. This was a result of poor geometry and high fan speeds needed for attachment. The tested geometry is less than ideal and has a long way to go before it is of a shape that would have the potential to reduce the pressure drag as much as Goldschmied claimed. Future efforts should be put forth optimizing the aft body to reduce the low pressure in front of the slot and improving aft entrance of the slot to allow for a smoother flow.
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Computational modelling of monocyte deposition in abdominal aortic aneurysmsHardman, David January 2011 (has links)
Abdominal aortic aneurysm (AAA) disease involves a dilation of the aorta below the renal arteries. If the aneurysm becomes sufficiently dilated and tissue strength is less than vascular pressure, rupture of the aorta occurs entailing a high mortality rate. Despite improvements in surgical technique, the mortality rate for emergency repair remains high and so an accurate predictor of rupture risk is required. Inflammation and the associated recruitment of monocytes into the aortic wall are critical in the pathology of AAA disease, stimulating the degradation and remodeling of the vessel wall. Areas with high concentrations of macrophages may experience an increase in tissue degradation and therefore an increased risk of rupture. Determining the magnitude and distribution of monocyte recruitment can help us understand the pathology of AAA disease and add spatial accuracy to the existing rupture risk prediction models. In this study finite element computational fluid dynamics simulations of AAA haemodynamics are seeded with monocytes to elucidate patterns of cell deposition and probability of recruitment. Haemodynamics are first simulated in simplified AAA geometries of varying diameters with a patient averaged flow waveform inlet boundary condition. This allows a comparison with previous experimental investigations as well as determining trends in monocyte adhesion with aneurysm progression. Previous experimental investigations show a transition to turbulent flow occurring during the deceleration phase of the cardiac cycle. There has thus far been no investigation into the accuracy of turbulence models in simulating AAA haemodynamics and so simulations are compared using RNG κ − ε, κ − ω and LES turbulence models. The RNG κ − ε model is insufficient to model secondary flows in AAA and LES models are sensitive to inlet turbulence intensity. The probability of monocyte adhesion and recruitment depends on cell residence time and local wall shear stress. A near wall particle residence time (NWPRT)model is created incorporating a wall shear stress-limiter based on in vitro experimental data. Simulated haemodynamics show qualitative agreement with experimental results. Peaks of maximum NWPRT move downstream in successively larger geometries, correlating with vortex behaviour. Average NWPRT rises sharply in models above a critical maximum diameter. These techniques are then applied to patient-specific AAAs. Geometries are created from CT slices and velocity boundary conditions taken from Phase Contrast-MRI (PC-MRI) data for 3 patients. There is no gold standard for inlet boundary conditions and so simulations using 3 velocity components, 1 velocity component and parabolic flow profiles at the inlet are compared with each other and with PC-MRI data at the AAA midsection. The general trends in flow and wall shear stress are similar between simulations with 3 and 1 components of inlet velocity despite differences in the nature and complexity of secondary flow. Applying parabolic velocity profiles, however, can cause significant deviations in haemodynamics. Axial velocities show average to good correlation with PC-MRI data though the lower magnitude radial velocities produce high levels of noise in the raw data making comparisons difficult. Patient specific NWPRT models show monocyte infiltration is most likely at or around the iliac bifurcation.
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Discrete and porous computational fluid dynamics modelling of an air-rock bed thermal energy storage systemLouw, Andre Du Randt 04 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Concentrating solar power promises to be a potential solution for meeting the
worlds energy needs in the future. One of the key features of this type of renewable
energy technology is its ability to store energy effectively and relatively
cheaply. An air-rock bed thermal energy storage system promises to be an effective
and reasonably inexpensive storage system for concentrating solar power
plants. Currently there is no such storage system commercially in operation
in any concentrating solar power plant, and further research is required before
such a system can be implemented. The main research areas to address are
the thermal-mechanical behaviour of rocks, rock bed pressure drop correlations
and effective and practical system designs. Recent studies have shown that the
pressure drop over a packed bed of rocks is dependant on various aspects such
as particle orientation relative to the flow direction, particle shape and surface
roughness. The irregularity and unpredictability of the particle shapes make it
difficult to formulate a general pressure drop correlation. Typical air-rock bed
thermal design concepts consist of a large vertical square or cylindrical vessel in
which the bed is contained. Such system designs are simple but susceptible to
the ratcheting effect and large pressure drops. Several authors have proposed
concepts to over-come these issues, but there remains a need for tools to prove
the feasibility of the designs.
The purpose of this paper is to investigate aDEM-CFD coupled approach that
can aid the development of an air-rock bed thermal energy storage system. This
study specifically focuses on the use of CFD. A complementary study focusses
on DEM. The two areas of focus in this study are the pressure drop and system
design. A discrete CFD simulation model is used to predict pressure drop over packed beds containing spherical and irregular particles. DEM is used to create
randomly packed beds containing either spherical or irregularly shaped particles.
This model is also used to determine the heat transfer between the fluid
and particle surface. A porous CFD model is used to model system design concepts.
Pressure drop and heat transfer data predicted by the discrete model, is
used in the porous model to describe the pressure drop and thermal behaviour
of a TES system.
Results from the discrete CFD model shows that it can accurately predict the
pressure drop over a packed bed of spheres with an average deviation of roughly
10%fromresults found in literature. The heat transfer between the fluid and particle
surface also is accurately predicted, with an average deviation of between
13.36 % and 21.83 % from results found in literature. The discrete CFD model for
packed beds containing irregular particles presented problems when generating
a mesh for the CFD computational domain. The clump logic method was used
to represent rock particles in this study. This method was proven by other studies
to accurately model the rock particle and the rock packed bed structure using
DEM. However, this technique presented problems when generating the surface
mesh. As a result a simplified clump model was used to represent the rock particles.
This simplified clump model showed characteristics of a packed bed of
rocks in terms of pressure drop and heat transfer. However, the results suggest
that the particles failed to represent formdrag. This was attributed to absence of
blunt surfaces and sharp edges of the simplified clumpmodel normally found on
rock particles. The irregular particles presented in this study proved to be inadequate
for modelling universal characteristics of a packed bed of rocks in terms of
pressure drop. The porous CFD model was validated against experimental measurement
to predict the thermal behaviour of rock beds. The application of the
porous model demonstrated that it is a useful design tool for system design concepts. / AFRIKAANSE OPSOMMING: Gekonsentreerde sonkrag beloof om ’n potensiële toekomstige oplossing te
wees vir die wêreld se groeiende energie behoeftes. Een van die belangrikste eienskappe
van hierdie tipe hernubare energie tegnologie is die vermoë om energie
doeltreffend en relatief goedkoop te stoor. ’n Lug-klipbed termiese energie
stoorstelsel beloof om ’n doeltreffende en redelik goedkoop stoorstelsel vir gekonsentreerde
sonkragstasies te wees . Tans is daar geen sodanige stoorstelsel
kommersieël in werking in enige gekonsentreerde sonkragstasie nie. Verdere navorsing
is nodig voordat so ’n stelsel in werking gestel kan word. Die belangrikste
navorsingsgebiede om aan te spreek is die termies-meganiese gedrag van klippe,
klipbed drukverlies korrelasies en effektiewe en praktiese stelsel ontwerpe. Onlangse
studies het getoon dat die drukverlies oor ’n gepakte bed van klippe afhanklik
is van verskeie aspekte soos partikel oriëntasie tot die vloeirigting, partikel
vormen oppervlak grofheid. Die onreëlmatigheid en onvoorspelbaarheid van
die klip vorms maak dit moeilik om ’n algemene drukverlies korrelasie te formuleer.
Tipiese lug-klipbed termiese ontwerp konsepte bestaan uit ’n groot vertikale
vierkantige of silindriese houer waarin die gepakte bed is. Sodanige sisteem
ontwerpe is eenvoudig, maar vatbaar vir die palrat effek en groot drukverliese.
Verskeie studies het voorgestelde konsepte om hierdie kwessies te oorkom, maar
daar is steeds ’n behoefte aanmetodes om die haalbaarheid van die ontwerpe te
bewys.
Die doel van hierdie studie is om ’n Diskreet Element Modelle (DEM) en numeriese
vloeidinamika gekoppelde benadering te ontwikkel wat ’n lug-klipbed termiese energie stoorstelsel kan ondersoek. Hierdie studie fokus spesifiek op
die gebruik van numeriese vloeidinamika. ’n Aanvullende studie fokus op DEM.
Die twee areas van fokus in hierdie studie is die drukverlies en stelsel ontwerp.
’n Diskrete numeriese vloeidinamika simulasie model word gebruik om drukverlies
te voorspel oor gepakte beddens met sferiese en onreëlmatige partikels.
DEM word gebruik om lukraak gepakte beddens van óf sferiese óf onreëlmatige
partikels te skep. Hierdie model is ook gebruik om die hitte-oordrag tussen die
vloeistof en partikel oppervlak te bepaal. ’n Poreuse numeriese vloeidinamika
model word gebruik omdie stelsel ontwerp konsepte voor te stel. Drukverlies en
hitte-oordrag data, voorspel deur die diskrete model, word gebruik in die poreuse
model om die drukverlies- en hittegedrag van ’n TES-stelsel te beskryf. Resultate van die diskrete numeriese vloeidinamikamodel toon dat dit akkuraat
die drukverlies oor ’n gepakte bed van sfere kan voorspel met ’n gemiddelde
afwyking van ongeveer 10%van die resultatewat in die literatuur aangetref word.
Die hitte-oordrag tussen die vloeistof en partikel oppervlak is ook akkuraat voorspel,
met ’n gemiddelde afwyking van tussen 13.36%en 21.83%van die resultate
wat in die literatuur aangetref word. Die diskrete numeriese vloeidinamika model
vir gepakte beddens met onreëlmatige partikels bied probleme wanneer ’n
maas vir die numeriese vloeidinamika, numeriese domein gegenereer word. Die
"clump"logika metode is gebruik om klip partikels te verteenwoordig in hierdie
studie. Hierdiemetode is deur ander studies bewys om akkuraat die klip partikel
en die klip gepakte bed-struktuur te modelleer deur die gebruik van DEM. Hierdie
tegniek het egter probleme gebied toe die oppervlak maas gegenereer is. As
gevolg hiervan is ’n vereenvoudigde "clump"model gebruik om die klip partikels
te verteenwoordig. Die vereenvoudigde "clump"model vertoon karakteristieke
eienskappe van ’n gepakte bed van klippe in terme van drukverlies en hitte oordrag.
Die resultate het egter getoon dat die partikels nie vorm weerstand verteenwoordig
nie. Hierdie resultate kan toegeskryf word aan die afwesigheid van
gladde oppervlaktes en skerp kante, wat normaalweg op klip partikels gevind
word, in die vereenvoudigde "clump"model. Die oneweredige partikels wat in
hierdie studie voorgestel word, blykomnie geskik tewees vir die modellering van
die universele karakteristieke eienskappe van ’n gepakte bed van klippe in terme
van drukverlies nie. Die poreuse numeriese vloeidinamika model is met eksperimentele
metings bevestig omdie termiese gedrag van klipbeddens te voorspel.
Die toepassing van die poreuse model demonstreer dat dit ’n nuttige ontwerp
metode is vir stelsel ontwerp konsepte.
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Designing Microfluidic Control ComponentsWijngaart, Wouter van der January 2002 (has links)
No description available.
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Designing Microfluidic Control ComponentsWijngaart, Wouter van der January 2002 (has links)
No description available.
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Reverzní vírová turbina / Reversible swirl turbinePalička, Miroslav January 2020 (has links)
This diploma thesis describes hydraulic design of Swirl turbine, dedicated to be used for tidal powerplant and study possibilities of the turbine to work in turbine, reverse turbine, pump and reverse pump regime. From individual regimes, graphical characteristics of created hydraulic design were created and compared, using CFD simulations.
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Zlepšení hydraulických vlastností vírových turbin / Improving of hydraulic properties of swirl turbinesKůrečka, Jan January 2016 (has links)
This diploma thesis describes design of blade geometry of swirl turbines with different blade row density for given parameters Q11 = 1,9 [m3s-1], n11 = 170 [min-1], H=2,5 m, and =0,8. Goal is to found out differences between designs with high count of runner blades and design with fewer blades. Comparison of computed characteristics of three, seven and nine bladed runners is given.
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CFD Analysis of Engine Room Temperature : CFD Analysis of Engine Room Temperature: Case study The Grange Castle Power Plant ProjectWanli, William January 2023 (has links)
Computational Fluid Dynamics (CFD) has emerged as an indispensable tool in various engineering fields, particularly in the design and optimization of HVAC systems in complex environments, such as engine rooms. This paper presents a comprehensive overview of CFD applications and focuses on the engine rooms of the Grange Castle Power Plant in Dublin, Ireland. Sustainable Development Capital LLP (SDCL) is constructing a state-of-the-art power plant at Grange Castle Business Park in Dublin, featuring six MAN 18V51/60DF engine generators and a total net export capacity of 111 MW. The plant uses pioneering dualfuel technology and serves as a contingency facility to stabilize the power grid amidst increasing integration of renewable energy. It functions as a responsive backup power generator and a peak load reducer, aiding the Irish government's goal of sourcing 80% of power from renewables by 2030. The initiative is part of a wider strategy including MAN Energy Solutions and Greener Ideas Limited, contributing to three new power plants in Ireland with a combined capacity of 311 MW.This study utilizes steady-state CFD simulations, employing the widely adopted k-epsilon turbulence model. Known for its robustness and computational efficiency, the k-epsilon turbulence model is utilized to analyse one engine cell at the Grange Castle Power Plant. As a two-equation model, it involves solving two additional transport equations alongside the Navier-Stokes equations to simulate fluid flow.Commonly applied in engineering applications, this model will be utilized to provide predictions of airflow and temperatures within the cell during standby and running states over the course of the year. By leveraging the strengths of the k-epsilon turbulence model, the study seeks to gain valuable insights into the complex fluid dynamics within the engine cell, ultimately helping to optimize its performance and efficiency. The analysis focused on one engine cell, with the setup and geometry for each cell being identical.Specifically, the research investigates maintaining the temperature within the cell, temperature distributions, airflow comparisons to design specifications and requirements, heating load and adequate airflow calculations, and potential benefits of optimizing the design and operation of the engine cell.The dimensions and characteristics of the engine room, along with the engines themselves and the heat they generate, play a significant role in the design process. In this study, there are several essential factors to consider, including a negative pressure ventilation system, as well as combustion and cooling air provided through air intake units that draw air from outside the engine hall and exhaust it using fans mounted on the roof. The ventilation system must be designed to maintain the room temperature within the range of 9 °C to 45°C at different points in the room. Since the engine combustion air will be drawn from inside the engine hall, the ventilation system must provide the required volumes of combustion air at all times, along with the necessary ventilation. The CFD analysis conducted in this study provides the groundwork for designing an effective ventilation system that can maintain optimal temperature conditions in the engine room. Using the simulation results, the ventilation system will be optimized to ensure the required temperature is maintained while also preventing the formation of explosive atmospheres.iiAlso, the simulation study presented in this report showcases the ability of CFD simulations to predict airflow and temperature fields in the engine room of a power plant. It is essential to understand the different scenarios' conditions to design a reliable and efficient engine room system. Furthermore, CFD simulations have proven to be an effective tool for optimizing HVAC installations to meet specific building requirements even before installing any equipment. CFD takes into account all factors influencing airflow and temperature, ensuring finely tuned designs even in confined spaces.To accurately analyse and simulate the environment, a 3D model of the engine and room is created using Inventor and AutoCAD software. However, for complex systems like the engine room, simplifying the geometry is necessary when preparing a CFD model. This is because including every detail can result in an excessive number of mesh elements, leading to longer simulation times and higher computational costs. Therefore, striking a balance between geometric complexity and computational efficiency is important for an optimal CFD model. By creating a simplified model, the CFD simulation can be more computationally efficient while still accurately capturing important flow features. The 3D model allows for seamless integration with the CFD software, enabling accurate representation of the environment for analysis.The study conducted simulations for a high-power diesel & gas engine room under four different scenarios, covering various seasonal and load conditions. The results indicated that a heating coil with a 250 kW capacity is required to preheat the airflow of 25.5 m³/s by 8 °C to maintain the required temperature above 9 °C during winter. Similarly, during summer, fans with an airflow rate of 60 m³/s are necessary to keep the engine room temperature below 45 °C. This analysis is critical for designing an optimal ventilation system in engine rooms, ensuring sufficient airflow and maintaining appropriate engine temperature to prevent engine start failure. The simulation results provide invaluable information for HVAC engineers to design an efficient and reliable engine room system.Through the utilization of CFD simulations, engineers can simulate and analyse the performance of the HVAC system under various conditions, providing them with the necessary information to make well-informed decisions to ensure that the system meets the required performance criteria. Implementing CFD in the early stages of HVAC design provides valuable insights, saving engineers time and money associated with real-life testing and validation. By leveraging CFD simulations, engineers can virtually test and evaluate multiple design alternatives, ventilation strategies, and system configurations prior to actual implementation. This proactive approach helps engineers pinpoint potential issues, optimize system design for enhanced efficiency and effectiveness, and minimize the need for expensive post-installation modifications and adjustments.
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Modélisation de l'aération naturelle et du microclimat des serres en verre de grande portée sous climat tempéré océaniqueOuld Khaoua, Sid-Ali 28 November 2006 (has links) (PDF)
Le "climat" à l'intérieur d'une serre dépend de son aération. Le processus d'aération est complexe, il participe à l'essentiel des échanges de chaleur et de masse avec l'extérieur, et sa maîtrise permet donc de contrôler les paramètres physiques tels que la température, l'humidité, ou les concentrations de gaz comme le CO2 par exemple. Ce contrôle est essentiel pour maintenir les plantes dans des conditions métaboliques favorables (respiration, photosynthèse, transpiration) et dans un état sanitaire satisfaisant.<br />La ventilation naturelle est le système le plus économique pour réguler le microclimat interne de la serre. Néanmoins, elle n'offre qu'un contrôle limité sur l'écoulement d'air dans la serre et reste difficile à maîtriser.<br />Cette étude contribue à l'analyse et à la modélisation des phénomènes mis en jeu dans l'aération naturelle des serres en verre, de grande portée, habituellement utilisées en culture ornementale (plantes en pots), sous climat tempéré, tel qu'en Anjou. Deux approches complémentaires incluant expérimentation in situ et modélisation mathématique du climat distribué sont mises en œuvre.<br />Des campagnes de mesures ont été menées à l'intérieur d'une serre de production et dans son environnement immédiat sous conditions réelles de culture ornementale. Des données météorologiques : température de l'air, vitesse et direction du vent, rayonnement solaire et atmosphérique, ont été collectées. L'ensemble de ces mesures constitue un jeu de données conséquent destiné à fournir les entrées du modèle numérique. Parallèlement à ces mesures, nous avons systématiquement procédé à des mesures du taux de renouvellement d'air qui ont été utilisées pour valider le modèle.<br />Un modèle numérique a été mis en œuvre. Il s'appuie sur un code de mécanique des fluides numérique (Computational Fluid Dynamics). Ce code permet de prédire les champs de vitesses et de températures à l'intérieur de la serre après résolution numérique des équations de base qui régissent les mouvements d'air (équations de Navier-Stokes couplées à l'équation de l'énergie) dans le domaine de calcul considéré. La turbulence, dont l'effet est loin d'être négligeable sous serre, a été modélisée à l'aide d'une fermeture de type k-e. Le taux d'aération a pu être déduit ensuite par résolution d'une équation de transport d'un gaz traceur virtuel. Un module radiatif a été ajouté dans le modèle numérique afin de prendre en compte le rayonnement d'origine solaire et atmosphérique. Ce module résout l'équation des Transferts Radiatifs qui est couplée à l'équation de l'énergie.<br />Ce modèle « complet » a pu être vérifié et validé pour différentes conditions climatiques. Il a été ensuite utilisé pour analyser l'impact de la configuration des ouvrants sur le climat et sur les flux de chaleur au niveau de la toiture de la serre. Cette analyse a porté non seulement sur la ventilation mais aussi sur l'homogénéité de la distribution des vitesses et des températures dans la serre et notamment au niveau des cultures.<br />Enfin, des indicateurs d'efficacité de l'aération de la serre sous climat estival ont pu être dégagés pour différentes configurations d'aération (ouverture) et différentes conditions climatiques.
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