Dissertations / Theses on the topic 'Ventilation – Noise'

Single-hole restrictors are widely used in the aircraft air distribution system (ADS). The noise generated due to the flow passing over the restrictor is a main interior noise source of the cabin. Prediction of the restrictor noise generation is important for a quite ADS design. This work experimentally and analytically studies the noise generation mechanisms of the single-hole restrictor. An experimental rig to investigate the restrictor self-noise and interaction noise generated by the turbulent wake produced by in-duct elements installed in the duct and impinging on the restrictor has been developed and constructed. Aeroacoustic measurements of the restrictor self-noise have been made both inside and in the far field of the duct. Two models have been developed to understand the restrictor noise generation mechanisms and predict the sound power level (PWL). One model is based on the surface pressure cross spectrum to compute the effective axial dipole distribution. The other is an extension of previous work and based on the static pressure drop across the restrictor. The restrictor dimension is shown to have a large effects on the restrictor noise generation. For the interaction noise generation, the important parameters including mean flow speed, restrictor dimension, turbulence level and characteristic length, that determine the sound power radiation spectrum are studied. A semi-empirical model has been developed to predict the sound power spectrum due to interaction noise. The link between the interaction noise generation and the restrictor surface pressure has been investigated. In addition to the investigation of the restrictor noise generation, this work conducted a short study into the use of surface roughness on the upstream side of the restrictor to reduce the noise generation whilst maintaining the pressure drop across it. It is shown that the noise generation can be reduced above the first cut-on frequency of the duct by increasing the upstream surface roughness.

In many kinds of buildings, the ventilation system constitute a well known source of broadband noise. Traditionally, duct born noise is attenuated using passive resistive silencers which produce a high level of attenuation over a broad frequency range. However, they tend to become large and bulky if designed for low frequency attenuation. The active noise control (ANC) technique is known for its ability to produce high levels of attenuation in the low frequency range even with a relatively moderate sized ANC system. Accordingly, a combination of active- and passive techniques, i.e. the construction of a hybrid active/passive silencer, provides a duct silencer solution of manageable size which also covers the low frequency range. However, adequate levels of attenuation are not likely to be obtained if the installation of the ANC system is not designed to account for the physical factors that may degrade its performance. This thesis focuses on applying ANC in ventilation systems, with particular emphasis on analyzing the limiting effect of some of these physical factors on the controller, and installation design for the purpose of reducing the influence of them. The degrading factors of particular interest include: flow induced noise in the microphone signals, acoustic feedback between the control loudspeaker and reference microphone, and standing waves and higher order acoustic modes inside the ducts. With respect to installation design, focus is also placed upon industry requirements for the ANC system. This has led to a module based approach, in which the microphones and the loudspeaker are installed in separate modules based on standard duct parts. This thesis is comprised of six parts. The first and third parts analyze the influence of flow-induced noise on the adaptive digital controller theoretically, through simulations and experiments. The second part describes investigations of several microphone installations intended to reduce flow induced noise. Further, results of measurements conducted in an acoustic laboratory according to an ISO-standard are presented. The attenuation produced by the ANC system was approximately 15-25 dB between 50-315 Hz, even for airflow speeds up to 20 m/s. The fourth part focuses on the possibility of using a passive silencer in combination with ANC, to reduce acoustic feedback and standing waves, while the fifth part investigates the possibility of using a passive silencer to reduce standing waves in the duct when the ANC system is not installed near the duct outlet. In ducts of larger dimensions, higher order acoustic modes may be in the frequency range adequate for ANC. The final part presents initial investigations concerning the feasibility of dividing a duct of large dimension into two more narrow ducts to remove higher order acoustic modes in the ANC frequency range, and the feasibility of applying single-channel ANC in each duct.

This thesis details a study of strategies used to limit the flow generated noise encountered in the outlet diffusers of high velocity heating, ventilation and air conditioning (HVAC) duct systems. The underlying noise rating criterion is drawn from the specifications covering ocean going aluminium fast ferries. Although directed primarily towards the fast ferry industry the results presented herein are applicable to other niche high velocity HVAC applications. Experimental tests have been conducted to prove the viability of a high velocity HVAC duct system in meeting airflow requirements whilst maintaining acceptable passenger cabin noise levels. A 50 mm diameter circular jet of air was expanded using a primary conical diffuser with a variety of secondary outlet configurations. Noise measurements were taken across a velocity range of 15 to 60 m/s. An optimum outlet design has been experimentally identified by varying the diffuser angle, outlet duct length and the termination grill. A 4 to 5 fold reduction in required duct area was achieved with the use of a distribution velocity of 20 to 30 ms-1, without exceeding the prescribed passenger cabin noise criteria. The geometric configuration of the diffuser outlet assembly was found to have a pronounced effect on the noise spectrum radiating from the duct outlet. The development of a numerical model capable of predicting the flow induced noise generated by airflow exiting a ventilation duct is also documented. The model employs a Large Eddy Simulation (LES) CFD model to calculate the turbulent flow field through the duct diffuser section and outlet. The flow-generated noise is then calculated using a far field acoustic postprocessor based on the Ffowcs-Williams and Hawkings integral based formulation of Lighthill???s acoustic analogy. Time varying flow field variables are used to calculate the fluctuating noise sources located at the duct outlet and the resulting far field sound pressure levels. This result is then used to calculate the corresponding far field sound intensity and sound power levels. The numerical acoustic model has been verified and validated against the measured experimental results for multiple outlet diffuser configurations.

This thesis studies the interaction of building energy use, ventilation performance and urban noise under future climate scenarios, comparing in particular the noise and climatic influences on non-domestic natural ventilation cooling. The main objective is to determine the level of climate change temperature increase that a noise reduction measure would mitigate. This involves quantifying the tension between maximising natural ventilation and maintaining good acoustic conditions. Methods are linked that are appropriate to a number of scales: ventilation aperture, whole-building, urban area, and the climate scale. Using the Finite Element Method (FEM), it was found that the sound transmission of ventilation apertures varied by up to 8dB across the frequencies considered. Noise mapping and whole building thermal performance were used to quantify natural ventilation potential and the impact of noise reduction measures. Three future climate data sets were compared and it was found that all sets provided acceptable information about future natural ventilation performance. The difficulty of adopting natural ventilation with the warming present in all the data sets was clear from the high levels of future overheating. Using these methods and a representative future weather data set, a number of design implications were illustrated, such as the reduction in sensible cooling per unit of ventilation airflow with higher summer temperatures. The main comparison of acoustic and climatic environmental influences showed that a 10dB noise reduction measure affecting natural ventilation could mitigate a summer temperature increase due to climate change of between 2.0°C and 3.4°C.

Ces travaux de doctorat portent sur la réduction du bruit d'origine aérodynamique émis par les ventilateurs et les doublets d'hélices contra-rotatifs. La méthodologie proposée consiste à intégrer des méthodes rapides et précises de prédiction des niveaux sonores dans le processus de conception. Cette thématique a vu son intérêt augmenter depuis que l'Union Européenne a restreint les limites d'exposition au bruit en milieu de travail et dans les zones habitées à proximité des aéroports. Parmi les méthodes numériques employées en aéroacoustique, les méthodes hybrides de prédiction du bruit sont considérées comme particulièrement appropriées pour la conception automatisée du fait de leur coût modéré en temps de calcul. Ces méthodes séparent la résolution de l'écoulement aérodynamique de celle de la génération du bruit et de sa propagation en champ lointain. L'écoulement aérodynamique est obtenu par simulation numérique, tandis que l'acoustique est traitée par méthodes analytiques. Ces méthodes analytiques développées et validées pour déterminer le bruit d'un profil aérodynamique placé dans un écoulement turbulent seront étendues pour traiter le réponse acoustique de pales en rotation. Ces travaux se concentrent sur deux configurations de ventilateurs basses vitesses. La première configuration traitée est le doublet d'hélices contra-rotatif de 4.2m de diamètre de la soufflerie L-1 de l'Institut von Karman (VKI). Ce système permet d'étudier le phénomène de bruit tonal et à large bande dû à l'impact des sillages turbulents, générés par l'hélice amont, sur l'hélice aval. La deuxième configuration traitée est un ventilateur à quatre pales du CETIAT (France) installé seul dans un large plenum. Ce système permet d'étudier le bruit propre ou bruit de bord de fuite causé par l'interaction des tourbillons générés par l'écoulement autour de la pale avec le bord de fuite de la pale. Pour cette configuration, des données expérimentales sont rendues disponibles dans le cadre d'un projet commun entre le VKI et le CETIAT. Les méthodes hybrides sont développées et mises en oeuvre pour ces deux mécanismes de bruit présents dans les deux configurations de ventilateur. L'objectif de ces travaux de thèse est d'employer les méthodes hybrides ainsi calibrées et validées pour réaliser l'optimisation du doublet d'hélices contra-rotatif de la soufflerie L-1. Le coeur de ces travaux portera sur l'extension des méthodes hybrides pour la prédiction du bruit d'un profil dans un écoulement turbulent uniforme au cas du bruit tonal et à large bande d'interaction de sillages et du bruit à large bande de bord de fuite dans des ventilateurs basses vitesses. Il sera montré qu'il est possible de déterminer le spectre de bruit de manière rapide et précise en s'appuyant sur la connaissance du champ aérodynamique dont les quantités seront extraites de simulations numériques stationnaires (RANS) pour alimenter la formulation analytique retenue. Cette dernière doit être adaptée au mécanisme de bruit étudié, à savoir l'interaction d'une pale de ventilateur avec un sillage ou celle du bord de fuite avec la turbulence qui s'est développé le long de la pale. Les deux mécanismes de bruit sont d'abord modélisés avec des fonctions analytiques qui sont calibrés avec les données des simulations numériques. Les modèles de sources de bruit ainsi que les estimations finales de spectre de bruit sont comparées aux données expérimentales disponibles et à des simulations directes. Enfin la méthodologie retenue est mise en oeuvre dans le cadre de l'optimisation du doublet d'hélices L-1 au moyen d'un algorithme génétique. L'étude détaillée de la sensibilité des paramètres et des contraintes de l'optimisation apporte un nouveau regard sur l'optimisation multi-objectif efficacité-bruit qui sera de plus en plus utilisée pour la conception de turbomachine dans le futur.
Abstract : The context of this thesis is the reduction of noise emitted by ventilation fans and aeronautical counter-rotating open rotors, which will be achieved by implementing fast and accurate noise prediction methods in the design process. The interest towards this subject has increased since the European Union enforced lower limits of exposure to noise in work environments and also to environmental noise in the proximity of airports. In the field of computational aeroacoustics, hybrid methods for noise prediction are considered particularly suitable for use in an automated design procedure due to their low computational cost. In fact they split the description of the flow field, which is made by computational fluid dynamics, from the quantification of the source of noise and of its propagation, obtained by using analytic formulations. Such analytic methods have already been used successfully for the prediction of the noise emitted by an airfoil placed in a turbulent flow; it is therefore natural to try to extend their applicability to the case of rotating blades. Two application cases have been chosen for this thesis. The first one is the 4.2 m diameter counter-rotating fan of the von Karman Institute (VKI) L1 low-speed wind tunnel, which is used to study the phenomenon of wake-interaction tonal and broadband noise. The second application case is a four-bladed low-speed ventilation fan in which the dominant source of noise is the trailing-edge or self-noise caused by the turbulent eddies passing over the trailing-edge of the blade. In this case, an experimental database has been made available by CETIAT, France, in the framework of a collaborative project with VKI. The final step of the project will be to use the prediction codes developed for both the noise phenomena in the geometric optimization of the L1 counter-rotating fan. The fundamental question that will be addressed in the thesis is how to extend the hybrid CFD-analytic methods to predict noise from an airfoil in a uniform turbulent flow to the case of tonal and broadband wake-interaction noise and trailing-edge broadband noise in low-speed fans. It will be shown that it is possible to provide a fast and reasonably accurate prediction of the spectrum of noise emitted by low-speed fans by extracting flow data from Reynolds Averaged Navier-Stokes (RANS) simulations and using them as input to Amiet's analytic formulation, provided that this has been carefully adapted to the studied noise generation phenomenon, i.e. the interaction of the leading-edge of a fan blade with an incoming wake or of the trailing-edge with the turbulent boundary layer over the blade surface. Concerning the methodology, both noise generation mechanisms will first be modeled with analytic functions, then the necessary flow field input will be extracted from RANS simulations and the models will be validated with respect to experimental data, whenever possible, or to higher fidelity simulations. The last step of the project is the application of these noise prediction methods to the shape optimization of the L-1 fan blades by means of a genetic algorithm. The sensitivity analysis of the design parameters and of the constraints used in the optimization process provides a new perspective on the multi-objective efficiency-noise optimization approach which will be increasingly used in turbomachinery design in the future.

The thesis deals with issues of noise ventilation outlets in a passenger car. There is a description of the noise reduction in the acoustic background, optimizing experimental measurement methodology and familiarization with measuring equipment. The next step includes measuring of individual outlet options, results post-processing and comparison of tested alternatives. Based on these results the best variants are chosen and measures for decreasing noise in the ventilation outlets are proposed.

Les activités humaines font peser sur l’écosystème marin de multiples pressions délétères. Pollution chimique, changement climatique, risque d’acidification, débris de plastique et déchets radioactifs ont des impacts sans précèdent. Une pollution de plus en plus reconnu comme majeur est la pollution sonore. La prospection sismique, le battage de pieux et le trafic maritime génèrent des niveaux sonores qui peuvent être extrêmement forts, modifiant fondamentalement le paysage acoustique sous-marin. On sait que de nombreux mammifères marins et poissons entendent le bruit généré par ces activités et que cela altère leur physiologie et leur éthologie. Par contre, chez les invertébrés marins très peu d’études avaient évalué leur capacité à entendre et l’impact de cette pollution sur eux reste à déterminer. Nous avons abordé le problème par une étude de la capacité de perception du son chez l'huître creuse Magallana gigas en utilisant une approche comportementale et physiologique. Nous avons montré que M. gigas entend dans la gamme de fréquences entre 10 et 1000 Hz. Cette analyse nous a permis de caractériser les sources de sons qui contribuent à leur environnement auditif. Au laboratoire, dans un milieu contaminé (i) au cadmium, un métal que nous avons considéré à la fois comme une substance toxique et un marqueur indirect de l'activité ventilatoire, et (ii), par des bruits de cargo, nous montrons un effet répresseur du bruit caractérisé par une diminution de l'activité valvaire, de l'activité ventilatoire et du taux de croissance. Nous rapportons également une diminution de la bioaccumulation du Cd dans les branchies et une modulation de l'expression de certains gènes. Nous avons enfin étudié sur un enregistrement de 2 ans dans le port commercial de Santander, le comportement (incluant les pontes et la croissance) de 3 groupes d’huitres exposés à une forte pollution sonore et à une « qualité de l’eau » considérée dans la littérature comme bonne à très bonne pour une masse d’eau fortement modifiée. Nous avons retrouvé dans notre analyse différents effets que nous avions provoqués ou prédits à partir du travail de laboratoire où nous avions manipulé le bruit seul. Nous concluons que la pollution sonore au sein du port doit diminuer le fitness des huîtres en modifiant leur activité valvaire, la hiérarchie de leurs rythmes biologiques et la croissance. Nos résultats suggèrent que la pollution sonore peut avoir des conséquences importantes sur les invertébrés et présente un risque fort en termes de productivité de l'écosystème
Human activities introduce multiple harmful pressures on the marine ecosystem. Chemical pollution, climate change, acidification risk, plastic debris and radioactive wastes have significant effects on marine wildlife. Noise pollution is now recognized as a major source of pollution at sea. Seismic exploration, pile driving and marine traffic, among other activities, generate noise at high sound pressure levels altering the underwater acoustic landscape. Many marine mammals and fish hear the noise generated by these activities which have the potential to alter their physiology and ethology. However, very few studies among marine invertebrates had assessed their ability to hear and the impact of noise pollution on them has yet to be determined. We approached the problem by studying sound perception ability in the pacific oyster Magallana gigas using behavioural and physiological techniques. We have shown that M. gigas is sensitive to sound in the frequency range from 10 to 1000 Hz. This characterization allowed us to define sound sources that contribute to their sound landscape. In the laboratory, in an environment contaminated with (i) cadmium, a metal that we considered to be both a toxic agent and an indirect marker of ventilatory activity, and (ii) cargo ship noise, we showed a depressant or repressant effect of noise characterized by a decrease in valve activity, ventilatory activity and growth rate. We also report a decrease in Cd bioaccumulation and some modulation of gene expression. Finally, we studied a 2-year behavioural record performed in the commercial port of Santander (including spawning events and growth) on 3 groups of oysters exposed to high noise pressure levels. In the port of Santander, the "water quality" is otherwise considered by the literature as good to very good for a heavily modified water body. We found in these records different changes that we previously induced and/or produced in the laboratory. We conclude that the noise pollution load occurring within a commercial port must reduce the fitness of oysters by modifying their valve activity, the hierarchy of their biological rhythms and their growth rate. Our results strongly suggest that noise pollution can have significant consequences on invertebrates and presents a high risk in terms of ecosystem productivity

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Bachelors
Nursing
Nursing

This thesis aims at preparing a user-friendly software tool for the prediction and analysis of the noise generated in Heating, Ventilating and Air Conditioning (HVAC) Systems elaborating the standardized prediction formulae and data coming from the research studies. For the analysis portion of the software, different types of indoor noise criteria are introduced and implemented in the software to ease the investigation of the level and the quality of the sound perceived by the occupant in a room through such criteria. General software structure and implementation of HVAC elements are explained by different userinterface samples in the thesis. Several case studies are presented to demonstrate the capabilities of the tool prepared in VISUAL BASIC programming language within the scope of the study.

The aim of the diploma thesis is to find out by measuring the production of carbon dioxide that man produces in various types of physical activity. Using the model, the goal is to simulate real carbon dioxide production for a type object and to design a way of automatic regulation, air supply and drainage to obtain better indoor environment (represented by carbon dioxide).

This thesis deals with the quality of the external and internal environment and the possibility of interaction. Resolves components, pollutants and sources of pollutants that are contained in the external and internal air and thus influence around us all. The theoretical part describes the resources, limit concentration or additional filtering of the individual substances. Are summarized in detail the possibility of air exchange and ventilation in buildings intended for public gatherings. Another part of the treatment methods solve indoor environmental quality (grade of primary school) according to the changes of air flow, ventilation options and the impact of external environment on indoor air quality. It also includes a proposal for forced ventilation of the building of the school. In the experimental part, I focused on the evaluation of the concentration of carbon dioxide in the external and internal environment and the possibilities of noise pollution. In conclusion, there are variants commented and evaluated.

The aim of the thesis "Design and optimization of the heat pump" is the project documentation for building permits, finding a suitable source of heat and cold. The problem is solved for a Tesco hypermarket. The device is designed to meet the health, performance and functional requirements for indoor climate. The task of this device is to transport fresh air into the interior cover heat losses in winter and coverage heat gains during the summer. The theoretical part deals with the problem of heat pumps. Special mention is about heat pump air x air. Calculation and design part is a specific proposal, two air conditioners and optimizing for winter. The experimental part deals with the processing of data on existing rooftop units.

This study concerns the development of a novel mechanical ventilation system, with a view to analysing the results of a new mechanical ventilation technique, referred to noisy ventilation. Additionally, the study addresses the assessment of the system, involving the estimation of certain mechanical parameters of the respiratory system under noisy ventilation and discusses a pilot trial in vivo, with a pig. During acute respiratory failure, intubation and invasive mechanical ventilation may be life saving procedures. The general aim of mechanical ventilation is to provide adequate gas exchange support, while not damaging the respiratory system. This technique is one of the most important life support tools in the intensive care unit. However, it may also be harmful by causing ventilator induced lung injury and other undesirable effects. There is a growing interest in the development and use of variable mechanical ventilation performing variable volume and variable pressure controlled ventilation. The reasons are that this technique can improve lung functions and reduce lung damage, when compared to standard mechanical ventilation. Moreover, variable ventilation can improve lung mechanics and gas exchanges. The new ventilation system has to have the capabilities to perform a noisy ventilation regime, besides the standard mechanical ventilation. The development started with commercial devices: a mechanical ventilator and a personal computer, whose roles were to execute the noisy ventilation regime and to implement the new ventilation pattern by means of a ventilation routine, commanding the mechanical ventilator. After these two components were working together, a bench test was performed, in which a calibrated measuring device and a mechanical lung simulator were utilized. Considering that the system was working properly, it was possible to validate it by analysing the results. As the mechanical properties of the respiratory system are important quantities to know, a parameter estimation method was developed, with a view to estimating some relevant properties, such as compliance, positive end--expiratory pressure, resistance and others. The estimates were related to the adopted model for the respiratory system. In this study, four models were discussed: first order linear model, flow dependent resistance model, volume dependent elastance model and second order linear model. For each one, all parameters were estimated and the outcomes from each estimation were compared with the others, with a view to finding relationships between them and to evaluating the goodness of each model. Furthermore, as some parameters could be adjusted directly in the devices, adjusted and estimated values could also be compared. Finally, one trial in vivo was performed, with a view to assessing the behaviour of the system in a real situation and to showing the developed system to the research team. The system was set to work in a noisy and in a standard ventilation regime. It showed reasonable results in terms of quality of ventilation as well as reliability and maintainability of the ventilatory regime, during the whole test period. The developed parameter estimation methods were utilized to estimate the mechanical respiratory properties of the animal under test and to find cross relationships between these outcomes and others, such as those from blood gas, ultrasonography and electrical impedance tomography.

Objectif - Réaliser une étude en morphométrie géométrique pour définir la variabilité des sinus frontaux et maxillaires au sein d’une population adulte et pour l’établissement du profil biologique des individus à partir de la géométrie des sinus frontaux et maxillaires.- Valider un modèle de simulation numérique des écoulements pour l’étude de la ventilation nasosinusienne chez l’adulte et observer l’influence de la conformation sinusienne sur la ventilation nasosinusienne.Nous avons défini 20 landmarks fiables et reproductibles pour les sinus frontaux et maxillaires. Nous avons décrit la variabilité des sinus frontaux et maxillaires au sein d’un échantillon de population adulte. Enfin, nous avons mis en évidence l’existence d’allométries pour les sinus frontaux et maxillaires mais aussi l’existence d’un dimorphisme sexuel pour la conformation des sinus maxillairesNous proposons un modèle fiable de simulation numérique des écoulements à partir d’examen tomodensitométriques. Sur la base de ce modèle, nous n’avons pas mis en évidence d’influence de la conformation sinusienne sur la ventilation nasale et le conditionnement thermique de l’air inspiré et expiré
Objectives - to conduct a morphometric geometric study in order to define the variability of the frontal and maxillary sinuses in an adult population and to determinate the sex of individuals - to validate a Computational fluid dynamic model of the nasal airflow and to describe the influence of the sinus conformation on the nasal airflow.We defined twenty reliable and reproducible landmarks for frontal and maxillary sinuses. We described the variability of the frontal and maxillary sinuses in an adult population sample. Finally, we highlighted the existence of allometries for frontal and maxillary sinuses but also the existence of a sexual dimorphism in the conformation of the maxillary sinusesComputational fluid dynamics:We offer a reliable model for numerical simulation of flows from CT examination. Based on this model, we have not shown any influence of the conformation on the nasal sinus ventilation and thermal conditioning of the inhaled and exhaled air. We showed no ventilation in the sinuses in the nasal respiratory cycle. Future studies will endeavor to define a humidity conditioning air model and a simulation model of production of NO and gas exchange between sinuses and nasal cavities

This master’s thesis focuses on effect of outer building construction on thermal load of space. The effect of translucent and non-translucent construction is discussed. The project of air-conditioning system is prepared for the two alternatives of the translucent construction, including the purchase price of the airconditioning system and glazing and the savings on summer cooling. Afterwards the period of the recovery of investment is calculated. The plan of the airconditioning system is connected to my bachelor’s thesis “Airconditioning in the car showroom”, the subject of which was the plan of the airconditioning system of the car showroom.

La ventilation nasale est vitale pour le nouveau-né, respirateur nasal exclusif. Le tiers antérieur des fosses nasales peut être modifié par une sténose congénitale de l’orifice piriforme, tandis leur partie postérieure peut être fermée par une atrésie choanale uni ou bilatérale ou par des lésions du nasopharynx.Les simulations numériques permettent d’analyser l’écoulement et le conditionnement de l’air en contournant les limites techniques et éthiques rencontrées in vivo. Devant la rareté des données dans la littérature, une étude de faisabilité a été nécessaire et concluante : les modèles numériques sont qualitativement proches de la réalité. Un travail sur les conditions physiologiques chez le nouveau-né a ensuite été réalisé, avec une méthodologie retravaillée. La reconstruction tridimensionnelle des fosses nasales est possible dès la naissance. La création d’une sphère centrée sur la pointe du nez, éloignant le domaine d’entrée de la zone d’intérêt, a permis d’analyser le rôle du tiers antérieur des fosses nasales.La valve nasale joue un rôle majeur en inspiration : perte de charge, accélération, guidage des flux et réchauffement de l’air. Les trois quarts du réchauffement ont lieu en amont du cornet inférieur. Une obstruction nasale entraîne une réduction des vitesses et une augmentation des températures de l'air. La simulation de l’inspiration d’air à 0°C a permis de constater que les fosses nasales permettent d’amortir les effets du refroidissement de l’air extérieur.Ce travail constitue une première approche de la physiologie de la ventilation nasale du nouveau-né par modélisation numérique, indispensable à la compréhension de la pathologie nasale néonatale
Nasal breathing is essential for the newborn, exclusive nasal breather. The anterior third of the nasal fossae may be modified by a congenital stenosis of the pyriform aperture, while their posterior part may be closed by unilateral or bilateral choanal atresia.Numerical simulations are a good means to analyze airflow and air-conditioning: they circumvent the technical and ethical limits encountered in vivo. Given the rarity of available data in the literature, a feasibility study was necessary and was conclusive: numerical models are qualitatively close to reality. A work on the physiological conditions in newborns was conducted, using refined methodology. The three-dimensional reconstruction of the nasal fossae is possible from birth. The creation of a sphere centered on the tip of the nose, moving the boundary conditions away from the area of interest, made it possible to analyze the role of the anterior third od the nasal fossae.The nasal valve plays a major in inspiration: it is a zone of pressure loss, acceleration, flow guidance and air warming. Three-fourths of the warming takes place upstream the inferior turbinate. A partial nasal obstruction modifies these results with lower velocities and higher temperature of the air. The simulation of the inspiration of cold air (0°C) has shown that the nasal fossae can dampen, without canceling, the effects of air cooling. This work is a first approach to the physiology of nasal ventilation of the newborn by numerical modeling, which is essential to the understanding of neonatal nasal pathology

Pour atteindre les objectifs de réduction de consommation et augmenter la flexibilité de la demande des bâtiments, il est nécessaire de disposer de modèles de prévision de charge de climatisation facilement diffusables sur site et performants qui permettent la mise en place de stratégies d’optimisation énergétique et d’effacement. Cette thèse compare plusieurs architectures de modèles inverses (« boite noire », « boite grise »). Un modèle semi-physique d’ordre 2 (R6C2) a été retenu pour prévoir la puissance de climatisation et la température intérieure moyenne en chauffage et en refroidissement. Il permet aussi d’interpréter des situations inédites (effacement), absentes de la phase d’apprentissage. Trois stratégies d’optimisation énergétique et d’effacement adaptées aux contraintes d’exploitation sont étudiées. La première permet d’optimiser la relance en chauffage afin de réduire la consommation et d’atteindre effectivement la température de confort le matin. La seconde stratégie optimise les températures de consigne sur une journée dans un contexte de prix variable de l’énergie, ceci afin de réduire la facture énergétique. Enfin, la troisième stratégie permet au bâtiment de s’effacer en limitant la charge tout en respectant des critères de confort spécifiés. Le modèle R6C2 et les stratégies ont été confrontés à un bâtiment réel (une école élémentaire). L’étude montre qu’il est possible de prévoir la puissance électrique et la température moyenne d’un bâtiment complexe avec un modèle mono-zone ; elle permet d’évaluer les stratégies développées et d’identifier les limites du modèle
To reach the objectives of reducing the energy consumption and increasing the flexibility of buildings energy demand, it is necessary to have load forecast models easy to adapt on site and efficient for the implementation of energy optimization and load shedding strategies. This thesis compares several inverse model architectures ("black box", "grey box"). A 2nd order semi-physical model (R6C2) has been selected to forecast load curves and the average indoor temperature for heating and cooling. It is also able to simulate unknown situations (load shedding), absent from the learning phase. Three energy optimization and load shedding strategies adapted to operational constraints are studied. The first one optimizes the night set-back to reduce consumption and to reach the comfort temperature in the morning. The second strategy optimizes the set-point temperatures during a day in the context of variable energy prices, thus reducing the energy bill. The third strategy allows load curtailment in buildings by limiting load while meeting specified comfort criteria. The R6C2 model and strategies have been faced with a real building (elementary school). The study shows that it is possible to forecast the electrical power and the average temperature of a complex building with a single-zone model; the developed strategies are assessed and the limitations of the model are identified

碩士
國立臺北科技大學
機電整合研究所
90
The purpose of this research is to study the sources and countermeasures of noise in the vicinity of a vent shaft in an underground railway tunnel. In this case, it is noted that the Tunnel Ventilation Fan (TVF) is the main cause of acoustic noise breakout, whereas the exhaust and intake port of vent shaft structure are located at-grade. This being a mandatory requirement applicable to local Environmental Protection Regulations. It is essential the entire noise propagation path shall be well planned and designed to comply with all governing codes/regulations. From this study it is intend to develop and create a set of useful assessment rules and simulation system criteria in this regard. An engineering approach will be utilized to provide noise isolation and protection measures. Such approach encompasses two phases: Phase one is the collection of relevant standard, theoretical formulas, standards, empirical formulas, etc. on attenuation criteria of individual muffling or noise isolation components or module employed along the propagation path. The data thus acquired as cited above will be used as the input criteria to set up a noise analysis and simulation model for vent shaft design. By comparing with previous field measured quantities, within a deviates of 10% of the simulated outcome, Basically, the outcome of this research could presumably, be applied in similar design and planning on noise mitigation measures associated with vent shaft.

碩士
逢甲大學
機械工程學系
88
The guided noise cancellation technique is the technique that adopts some guiding mechanism to guide the noise and to cancel it. It can either guide the noise to cancel itself by the active noise cancellation principle, or guide the noise to some sound trap mechanisms then cancel it by the passive noise cancellation principle. This study extended the one-dimensional noise sound cancellation technique of sound pipes to the two-dimensional noise sound cancellation technique of double walls. It proposed a scheduling method of silence region design. It is for designing the silence region of a room based on both results of the theoretical analysis and computer simulations. The results of computer simulations can support the feasibility of this approach, the study results of this report can be useful for the future reference of silence region design.

碩士
國立雲林科技大學
工程科技研究所
105
In recent years, with the rise of environmental awareness, how to develop high-performance fan to reduce the rising room temperature, and not too much electricity consumption is a big problem. The exhaust fan can not only help the room to maintain a good room temperature, but also help the indoor dirty air discharge can help improve the indoor air quality, when the fan speed is higher and also face the problem of noise, the main purpose of this study is to use Taguchi method in the application of low noise and high performance indoor ventilation fan research, apply Taguchi method can solve a large number of complicated experiments, can effectively establish an empirical formula in the simulation software Ansys to make the experimental conditions consistent, The error of the experiment increases the reference and accuracy of the experimental results.

碩士
國立臺灣科技大學
建築系
104
As the trend of building sustainability in recent years, the design requirements of architectural acoustics performance increased. Effective natural or hybrid ventilation system is helpful to reduce air-conditioning energy consumption. On the other hand, natural ventilation strategies challenged the common practice in acoustic design. Case studies on building acoustic solutions associated with natural ventilation were reviewed with a large auditorium that induces heat evacuation. Carry out the hall interior space flow field simulation by analysis using CFD method. And calculate the external noise sound pressure by BEM method. Discuss the feasibility of applying natural ventilation strategies and buoyancy ventilation tower in an auditorium space, with the variation of the size of the exhaust opening.

Noise control in the heating, ventilation and air-conditioning (HVAC) systems is one of the critical design parameters in measuring the occupant comfort. The noise generated by air-handling units propagates through the ducts in the axial as well as transverse direction. Noise radiated in the transverse direction from the duct walls excited by the internal sound field is called the breakout noise. An analytical formulation has been developed in this thesis in order to predict the breakout noise by incorporating three-dimensional effects along with the acoustical and structural wave coupling phenomena. The first step in the breakout noise prediction is to calculate the interior acoustic response and flexural vibration displacement of the compliant walls. Dynamic interaction between the internal acoustic subsystem and flexible structural subsystem has been expressed in terms of the modal characteristics of the uncoupled response of the acoustic and structural sub-systems. Solutions of the inhomogeneous wave equation are rearranged in terms of impedance and mobility, and the equations describing the complete system are expressed in terms of matrices, which result in a compact matrix formulation. Examples of the formulation are a rectangular cavity with one flexible wall and a rectangular cavity with four-flexible walls. The formulation is modified to incorporate complex boundary conditions by means of appropriate Green’s functions. It is implemented for flexible wall duct using the modified cavity Green’s function. Another objective of the present investigation is to understand the coupling phenomenon and its effect on the compliant wall vibration displacement. The developed three-dimensional analytical analysis of the breakout noise is convenient to implement on the computer, and also to extend the sub-system level model to the system level model in order to analyze a complex acoustic-structural system for the breakout noise problem. The extent of coupling is calculated using a transfer factor based on the uncoupled natural frequencies of the acoustic and structural subsystems. It is observed from the free vibration analysis that a coupling between the cavity and the flexible panel exists in the vicinity of an uncoupled acoustic natural frequency. If a strong coupling occurs between an acoustic mode and a panel mode, then damping of structural subsystem would control it. The cavity volume changes stiffness of the panel, which in turn affects noise radiation in the stiffness-controlled region. The second step is to calculate the sound power radiated from complaint wall. The wall vibration velocity is a linear combination of the uncoupled flexural modes of the structural subsystem. It is substituted into the Rayleigh integral and Kirchhoff– Helmholtz (KH) integral formulation to predict the sound pressure radiated by the vibrating duct wall. The radiated sound power can be obtained by integrating the acoustic intensity over the surface of the flexible duct wall making use of appropriate expressions for radiation impedance. The radiation impedance terms involve a quadruple integral. Evaluation of this integral is quite complex and poses formidable computational challenges. These have been overcome by means of a co-ordinate transformation. Sound power radiation from flexible walls of the plenum and duct walls has been calculated using an equivalent plate model. Analytical results are corroborated with numerical models. The second part of thesis deals with a one-dimensional model to predict the breakout noise from a thin rectangular duct with different end conditions like anechoic termination, rigid-end termination, and the open-end termination. This model incorporates acoustic reflection effects in the duct internal sound field by using standing wave pattern by means of the transfer matrix approach. A one-dimensional prediction method based on the four-pole parameters has been developed to evaluate the lagged duct performance in terms of the breakout noise reduction. Radiation impedance of a duct is calculated by three different methods: (i) finite line source model (ii) finite cylinder model, and (iii) equivalent plate model based on fundamental bending mode of the duct. It is observed that the proposed model that uses the equivalent plate model for the lagged duct and the line source model for the bare duct is appropriate to predict the transverse insertion loss of the lagging, particularly at the lower frequencies that are of primary interest for reducing the breakout noise of rectangular ducts. The bare duct breakout noise results are compared with those of the corresponding 3-D analytical models. It shows that the one-dimensional model captures the overall mean pattern of breakout noise very well. The third part of the thesis examines the internal acoustic field and thence the transmission loss (TL) of a rectangular expansion chamber, the inlet and outlet of which are situated at arbitrary locations of the chamber; i.e., the sidewall or the face of the chamber. The four-pole parameters have been expressed in terms of an appropriate Green’s function of a rectangular cavity with homogeneous boundary conditions. A transfer matrix formulation has been developed for the yielding-wall rectangular chambers by considering structural-acoustic coupling. It may be combined readily with the transfer matrices of the other constituent elements upstream and downstream in order to compute the overall transmission loss or insertion loss. Wherever applicable, parametric studies have been conducted to evolve the design guidelines for minimizing the breakout noise from the HVAC ducts, plenums and cavities.

Klinischer Hintergund: Patienten mit akutem Lungenversagen (Acute respiratory distress syndome, ARDS) bedürfen intensivmedizinischer Behandlung. Die maschinelle Beatmung spielt dabei eine zentrale Rolle. Um einer zusätzlichen ventilatorassoziierten Lungenschädigung (ventiator induced lung injury, VILI) vorzubeugen, wird vom ARDS network die Beatmung mit niedrigem Atemzugvolumen empfohlen. Das Zulassen von Spontanatmung und Variabilität in der Druckunterstützung sind weitere Beatmungsstrategien, welchen in verschiedenen Studien positive Effekte im Bezug auf pulmonale Entzündungsreaktion, Schädigung des Lungengewebes und Gasaustausch zugeschrieben werden. Eine weit verbreitete Form der assistierten Spontanatmung ist die druckunterstützte Beatmung (Pressure Support Ventilation, PSV), bei der jede inspiratorische Atembemühung mit stets demselben Druck unterstützt wird. Es resultiert eine relative geringe Atemvariabilität. Eine weitere häufig angewandte Form der assistierten Spontanatmung ist die proportionale Druckunterstützung (Proportional Assist Ventilation, PAV). Hier verhält sich das Maß der Druckunterstützung proportional zu den inspiratorischen Bemühungen des Patienten. Entsprechend führt PAV, abhängig von der intrinsischen Variabilität des Patienten, zu einer höheren Variabilität an Atemzugvolumen und Atemfrequenz. Eine neuere Form der assistierten Spontanatmung ist die variable druckunterstützte Beatmung (noisy PSV), welche ebenfalls die Variabilität von Atemzugvolumen und Atemfrequenz erhöht. Im Unterschied zu PAV ist die Variabilität der Druckunterstützung extrinsisch und wird durch das Beatmungsgerät vorgegeben. Fragestellung /Hypothesen: Die vorliegende Studie untersucht die Therapieeffekte von noisy PSV, PAV und PSV auf pulmonale Entzündungsreaktion, Schädigung des Lungengewebes sowie Ventilationsverteilung im ARDS-Modell Surfactant depletierter Schweinelungen. Folgende Hypothesen wurden dazu formuliert: 1. Unter Noisy PSV zeigt sich eine Umverteilung der regionalen Ventilation von ventral nach dorsal. 2. Unter Anwendung von noisy PSV kommt es zu einer geringeren Schädigung des Lungengewebes im Vergleich zu PAV und PSV. 3. Noisy PSV kann die Entzündungsreaktion gegenüber PAV und PSV senken. Material und Methoden: 24 Jungschweine mit einem mittleren Körpergewicht von 31,3 kg (26,8 – 34,4 kg) wurden anästhesiert, intubiert und mechanisch beatmet. Die Lungenschädigung wurde mittels wiederholter Kochsalzlavagen herbeigeführt bis ein stabiles Verhältnis von arteriellem Sauerstoffpartialdruck zur inspiratorischen Sauerstofffraktion von unter 200 mmHg erreicht war. Dies entspricht der Definition eines moderaten ARDS. Nach Spontanisierung der Atmung folgte die Randomisierung der Versuchstiere zu einer der drei assistierten Beatmungsmodi noisy PSV, PAV oder PSV. Die Beatmung erfolgte jeweils mit einem mittleren Atemzugvolumen von 6 ml /kg KG über einen Zeitraum von sechs Stunden. Es wurden impedanztomographische Messungen zur regionalen Ventilationsverteilung durchgeführt. Untersuchungen zur pulmonalen Entzündungsreaktion und histologischen Schädigung des Lungengewebes wurden post mortem vorgenommen Zusätzlich erfolgten Messungen zu Hämodynamik, Atemmechanik und Gasaustausch. Außerdem wurden Atemmuster und die Variabilität der Atmung analysiert. Die Ergebnisse dieser Messungen sind jedoch nicht Gegenstand dieser Dissertation und werden an anderer Stelle diskutiert. Ergebnisse: PAV, nicht jedoch noisy PSV, führte zu einer Umverteilung der regionalen Ventilation von zentral nach dorsal im Vergleich zu PSV. Für den kumulierten DAD Score ließen sich keine signifikanten Unterschiede zwischen den Gruppen nachweisen. In schwerkraftunabhängigen Lungenabschnitten zeigten sich weniger interstitielles Ödem für PAV und noisy PSV im Vergleich zu PSV sowie weniger Hämorrhagie für PAV und PSV im Vergleich zu noisy PSV. Auch ergab sich ein geringeres Maß an Überdehnung für PAV im Vergleich zu PSV. In schwerkraftabhängigen Lungenabschnitten kam es unter noisy PSV zu einer Reduktion von interstitiellem Ödem im Vergleich zu PSV. Insgesamt, für schwerkraftabhängige und schwerkraftunabhängige Regionen zusammen betrachtet, zeigten sich weniger Hämorrhagie für PAV im Vergleich zu noisy PSV sowie weniger interstitielles Ödem für PAV und noisy PSV im Vergleich zu PSV. Unabhängig von der Therapieform war weniger Hämorrhagie in schwerkraftunabhängigen im Vergleich zu schwerkraftabhängigen Lungenabschnitten zu beobachten. Für den Gehalt an mRNA für IL-1, IL-6, IL-8, TNF-α, TGF-ß, Amphiregulin und Tenascin-c im Gewebe sowie für die Konzentration TNF-α und IL-8 im Lungengewebe, TNF-α im Blutplasma sowie IL-8 in den Proben der BAL ließen sich ebenso keine signifikanten Unterschiede zwischen den Gruppen nachweisen wie für die Proteinkonzentration in der BAL-Flüssigkeit und die Wet-/Dry-Ratio des Lungengewebes. Schlussfolgerungen: In diesem Modell des akuten Lungenversagens am Schwein resultierte eine 6-stündige Beatmungstherapie mit variabler Druckunterstützung, proportionaler Druckunterstützung oder konstanter Druckunterstützung in einer vergleichbaren Schädigung des Lungengewebes ohne wesentliche Unterschiede in der Entzündungsreaktion.

This diploma thesis deals with the basic theoretical overview of air-conditioning noise, the description of individual devices used in ventilation and active ventilation during storage of cereals. It also describes the possibilities of application of silencers for these devices. In the practical part, it focuses on the noise measurement in the post-harvest line and the design of appropriate noise measures to meet the under-noise levels.