Dissertations / Theses on the topic 'Airflows'
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Baillie, Neil Alexander. "Modelling nasal airflows." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419445.
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Paterson, Colin. "Thin fluid films subject to external airflows." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=22389.
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We use lubrication theory to analyse the steady flow of thin ridges, rivulets and rings of fluid and, in particular, we study the behaviour when the fluid is in the presence of an external airflow. Firstly, a thin ridge on an inclined planar substrate subject to a spatially varying pressure gradient due to an external airflow is considered. The effect of increasing the strength of the external airflow, and of increasing the inclination of the substrate to the horizontal, on a ridge of prescribed constant volume is investigated, and we identify and quantify the conditions for the ridge to de-pin at one or both of its contact lines. Secondly, we describe the possible pinning and subsequent de-pinning of a thin rivulet with constant nonzero contact angle as well as the possible de-pinning and subsequent re-pinning of a thin rivulet with constant width as they flow with prescribed volume flux in the azimuthal direction from the top to the bottom of a large horizontal cylinder. Thirdly, this problem is extended to include the effects of a prescribed uniform azimuthal surface shear stress arising from an external airflow in the direction opposing gravity. Lastly, we consider a thin ring of fluid with constant width and constant mass that flows in the azimuthal direction all the way round a large horizontal cylinder (a "full ring" of fluid) subject to a prescribed uniform azimuthal surface shear stress due to an external airflow. In particular, there is a maximum mass of fluid above which no full-ring solution exists, and we show that backflow near the cylinder surface is possible.
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Ramadhan, Abdulmajeed A. "Electrohydrodynamic driven airflows for microelectronics thermal management." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/21163/.
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The increasing demand for effective and compact thermal solutions for the next generation of thin and high-power density consumer electronics is challenging the capability of miniature mechanical systems to meet the required cooling performance. Due to their attractive and unique advantages with no moving parts, design flexibility, small-scale structure, low height profile, silent operation, and effective flow generation, electrohydrodynamic (EHD) air movers are well positioned to become a key emerging cooling technology as alternative to conventional rotary fans. In its general objective, this thesis aims to investigate the benefits and highlight the features of EHD air movers as a thermal management cooling solution in advanced and small-scale microelectronics, supporting all previous efforts in this direction. Due to the strong influence of the geometric parameters of EHD devices on the corona discharge process and the resulting EHD flow, numerical modelling represents a powerful tool to design and optimize EHD devices, especially of complex and small-scale structures, where the capability of experimental investigations is limited or challenging. This study presents an accurate and validated numerical method to solve the coupled equations of electrostatics, charge transport and fluid flow for the two-dimensional (2D) modelling of EHD airflow induced through a wire-to-plane/grid channel configuration, and is the first to develop a three-dimensional model (3D) that couples the EHD flows with conjugate heat transfer modelling. Based on thermal management requirements and from a design perspective, a comprehensive investigation and analysis into the influence of geometric parameters on the efficiency of EHD wire-to-grid blowers is performed and optimal configurations are proposed for a range of heights from 9 to 15 mm. Results reveal that using fine emitter wires is more efficient than thicker ones, and the grounded electrode locations affect significantly the electric field distribution and the blower efficiency. It is also found that using the grid as a further collector increases the blower performance, with higher flow production, lower operating voltage and reduced blower size. Further numerical developments are devoted to optimize the configuration of miniature wire-to-plane EHD blowers for heights up to 10 mm, which is the most preferred geometry for integration in the cooling systems of thin electronic applications. For ranges of fixed operating power and voltage, the efficient optimized electrode gaps are predicted and defined by simple expressions. The influence of channel sidewall on the EHD flow rate and velocity profile are investigated and the results show that the 2D modelling is valid to effectively predict flow rates produced by wide and short EHD blowers compared to that obtained by 3D simulations. A combined EHD air blower that enables a reduction in the level of applied voltage and a control of flow production is developed. Performance comparisons against commercial rotary blowers demonstrate that the optimized miniature EHD blowers are more competitive for cooling miniaturized and extended heated surfaces based on blower size, flow rate with uniform velocity profile, and power consumption. A novel design of an EHD system integrated with compact heat sinks is presented as a thermal management cooling solution for advanced and thin consumer applications. Results of a parametric study demonstrate that the EHD system offers flexible structure design with the ability to reduce the height and increase the width as required, providing a unique feature to be installed in low-profile laptops. Moreover, compared to traditional cooling systems used in the current standard low power laptops, the proposed EHD system offers promising cooling performance with higher thermal design power (TDP), reduced thermal solution volume and lower height profile.
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Jalil, Latif Imran. "Stabilising airflows in chilled ceiling/displacement ventilation environments." Thesis, De Montfort University, 2005. http://hdl.handle.net/2086/4237.
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Wallaart, Johannes Christiaan Safety Science Faculty of Science UNSW. "Identification, elimination and reduction of barriers to the effective use of respiratory personal protective equipment." Publisher:University of New South Wales. Safety Science, 2008. http://handle.unsw.edu.au/1959.4/43293.
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This thesis is concerned with the identification, elimination and reduction of barriers to the use of personal respiratory protective equipment (RPE) in the workplace to reduce and prevent occupational inhalation disease. Respiratory Protective Equipment (RPE) is widely used in industry, health, emergency response, military settings and many other applications and are in daily use by thousands of people in Australasia. The equipment is generally used to filter or ab/adsorb the contaminants from the air prior to delivery to the wearer by filtering or ad/absorbing contaminants from the air prior to being breathed. There is increasing concerns being expressed worldwide as well as in Australia and New Zealand about the apparent increase in diagnosed occupational diseases and the use of RPE is an essential preventative measure able to be adopted by workplaces. The use of this type of equipment is the option after the preferred options of elimination and isolation of the individual from the contaminant in the atmosphere. In spite of this, many different types of RPE are routinely in use. There are, however, enormous practical, physiological and psychological difficulties in the wearing of RPE. Concerns have been expressed in the literature as well as in practical situations that many different types of RPE was unable to meet the needs of workers, particularly as related to airflows and that current standards did not reflect the real-life workplace demands. This work set out to determine an improved methodology for users to determine the total inward leakage (TIL), the different types and quantities of airflows, particularly Peak Inspiratory Air Flows (PIAF). When communicating (an essential aspect in the workplace for safety reasons), PIAFs rise dramatically. This work showed that PIAF were very high, particularly when communicating, and is likely to exceed the ability of many commercial types of commercially available respiratory equipment as well being in excess of the certification requirements of standard bodies. In addition, Minute Volumes (MV) in a typical Australian workforce were shown to be very variable between individuals and current certification requirement of airflows do not appear to reflect practical use. The thesis further investigated using a questionnaire survey, the knowledge and current intervention measures adopted by farmers in different sections of agriculture, particularly dairy farming. Agriculture in New Zealand is a critical economic activity, employing 10% of the total workforce. This work showed that in spite of many different types of intervention activity spread over many years by Government agencies and private organisations to date, limited awareness exists of inhalation diseases and appropriate types of RPE in different applications (for example, confined space applications). The research would suggest that a different and more intensive approach is needed by Government agencies to address the problem in this workplace community if workplace inhalation diseases are to be reduced in the future.
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Li, Jain-Guo. "A study of thermally-induced Meso-scale airflows over inhomogeneous terrain." Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266253.
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Wood, Graeme Brendon. "The quantification of airflows generated by rotating rollers in wool carding machines." Thesis, University of Canterbury. Department of Mechanical Engineering, 2001. http://hdl.handle.net/10092/2281.
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The properties of fibres make them easily manipulated by aerodynamic forces. The carding
machine, used in cotton and wool processing, is an example of equipment that creates
aerodynamic forces due to fast rotating cylinders with rough surfaces. These forces are
generally seen as an undesirable side effect in fibre processing machinery, exacerbated with
modern equipment using faster rotating components.
This work attempts to quantify these aerodynamic forces on carding machines used in the
wool industry. A combination of boundary layer theory, experiments using hot wire
anemometry and flow visualisation, and Computational Fluid Dynamics (CFD) software
(Fluent) was used to build up an understanding of aerodynamics in the example of wool
carding machines. The theoretical and experimental work progressed along the following
topics to determine each effect on carding machine aerodynamics: rough surfaces,
centrifugal forces, three-dimensional edge effects, and interactions between rotating
cylinders. Examples from each section were modelled using CFD, which was found to
accurately simulate theoretical and experimental results in most cases. It could also
accurately predict the complex two-dimensional airflow patterns occurring in carding
machines. The CFD simulations underestimated the degree of turbulence generated by
interactions between rotating cylinders. Three-dimensional effects were overestimated, due
in part to attempting to apply the results of an oversimplified model to a full-scale carding
machine.
In undertaking this work, it was found the universal velocity distribution equations
describing flow over flat plates (for both smooth and rough surfaces) could also be used for
flow induced by rotating cylinders by compensating for curvature effects.
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Abdelhafez, Ahmed. "Effect of swirl on the choking criteria, shock structure, and mixing in underexpanded supersonic nozzle airflows." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9196.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Szleper, Michele Lee. "Converging nozzle design for a subsonic wind tunnel to test heat sinks under impinging and parallel airflows." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17124.
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Pálsson, Daði Snær. "Hybrid Ventilation : Simulation of Natural Airflow in a Hybrid Ventilation System." Thesis, KTH, Installations- och energisystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-146761.
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This thesis investigates the possibilities of using hybrid ventilation in an office building in Stockholm. The focus is on simulating the natural airflow to find out for which conditions it is sufficient. The thesis is done at White Arkitekter AB in cooperation and under the supervision of environmental specialists working there. A literature study is carried out to study what has been done before in Sweden as well as in other countries. Computer simulations are used to simulate the airflow to examine the conditions and architecture. A synthetic computer model representing a realistic office building is built up as a starting point. The ventilation method for the natural ventilation part is to take air in through the fa\c{c}ade and use the stack effects in an atrium for natural ventilation. By altering the architecture and the sizes of the openings according to the results from the simulations the building is dimensioned and formed to cope with the rules and requirements about the indoor air quality in workplaces. The simulations are done with a multi zone energy performance simulation tool that can simulate airflows and indoor air climate conditions in the zones as well as the energy consumption. Computational fluid dynamics calculations are then used to more closely simulate the conditions within the zones. The results from those simulations suggest that the natural ventilation as a part of a hybrid ventilation works for all the floors of the building for up to 10$\,^{\circ}\mathrm{C}$. The computational fluid dynamics simulations showed that the thermal comfort of all the occupants is fulfilled for these conditions but there is a risk of occupants experiencing draught because of to high velocities in the air especially for the colder outdoor temperatures. For the higher outdoor temperatures the airflow needs to be enforced to ensure sufficient conditions for the occupants and for the colder temperatures mechanical ventilation is needed to decrease heat losses and avoid the risk of draught.
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Körner, Max Konrad [Verfasser], Andre [Akademischer Betreuer] Thess, Bodo [Gutachter] Ruck, and Olga [Gutachter] Shishkina. "An Experimental Method for the Investigation of Indoor Airflows in a Reduced Scale Model Room : Development and Application / Max Konrad Körner ; Gutachter: Bodo Ruck, Olga Shishkina ; Betreuer: Andre Thess." Ilmenau : TU Ilmenau, 2014. http://d-nb.info/117818305X/34.
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Rydberg, Adam, and Alexandra Lindesvik. "Analys och ekonomisk utvärdering av två metoder för att lufttäta flerbostadshus." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Byggnadsteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-36933.
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Syfte: Syftet är att genom en strukturell jämförelse av fallstudiens undersökningsobjekt få en överblick över kostnaden för arbetsutförandet av två luttätnings- och provtryckningsmetoder. Detta för att ta fram vilken metod som är lämpligast att tillämpa med avseende på kostnad. Metod: Metoderna som tillämpats för att besvara målet var observationer, mätningar, beräkningar, litteraturstudie samt intervjuer. Den huvudsakliga metoden som användes var observationstekniken ”observatör som deltagare”. Intervjuer tillämpades för att anbringa ny kunskap men även verifiera empirin hämtad från observationerna. Resultat: Studien visar att det finns både mindre och markanta skillnader mellan objektens lufttätnings- och provtryckningsmetoder som genererar både för och nackdelar. De största skillnaderna var framförallt vid fönster- och dörrutförandet, materialvalet i installationsväggen och om en tidig provtryckning utförs eller inte. Fördelarna med Gripen var att de inte var beroende av utomstående aktörers utförande vid fönsteranslutningen samt att de hade ett moment mindre under kontrollen av klimatskalet. Studien visar även att Gripen hade en lägre totalkostnad för lufttäthetsarbetet än Vimans Trädgård. Dock var kostnaden per kvadratmeter desto högre för varje färdigställd kvadratmeter. Efter en noggrann strukturell jämförelse bedömdes Vimans Trädgårds tillvägagångssätt var den mest kostnadseffektiva lufttätnings- och provtryckningsmetoden utifrån kr/kvm, se Tabell 13. Konsekvenser: Studien visar att båda objektens metoder fungerar för att nå byggnadens ställda lufttäthetkrav. Då metoderna liknade varandra på många punkter kunde slutsatsen dras att lufttätningsutförandet av fönster- och dörranslutningar hade en stor inverkan på tiden samt kostnaden. Slutligen kan följande rekommendationer ges, en byggnads lufttäthet bör säkerställas i ett tidigt skede, företagens luftätningsmetoder bör fortsätta utvecklas samt en enhetlig lufttätnings- och provtryckningsmetod bör utformas och appliceras inom hela företaget. Begränsningar: Rapportens undersökningsstrategi är en kvantitativ fallstudie. Studien begränsas till fallstudiens båda undersökningsobjekt och deras lufttätnings- samt provtryckningsmetod utan avseende till materialkostnader. Undersökningen begränsas även till objektens förutsättningar som materialval men tar ingen hänsyn till geografisk placering eller väderstrecksorientering. Detta medför att studien är giltig under specifika förhållanden. Vid en eventuell upprepning kan studien påvisa andra resultat och generera skilda slutsatser än det som vidtagits i denna utredning.Purpose: The purpose is to provide an overview of the cost of the work performance of two air tightening and pressure testing methods through a structural comparison of the case study's investigative objects. This is to find out which method is most appropriate to apply in terms of cost. Method: The chosen methods, used to answer the goal, were observations, measurements, calculations, literature studies and interviews. The main method used was the observation technique "observer as a participant". Interviews were applied to conceive new knowledge, but also to verify the information from the observations. Findings: The study shows that there are both minor and significant differences between the objects air tightening and pressure testing methods that generate both pros and cons. The main differences were mainly the execution of the windows and doors, the choice of materials in the installation wall and if an early pressure test is performed or not. The benefits of Gripen were that they were not dependent on external operator’s performance at the window connection and that they had a moment less under the control of the climate scale. The study also shows that Gripen had a lower total cost of air tightness than Vimans Trädgård. However, the cost per square meter was the higher for each completed square meter. After a careful structural comparison, Vimans Trädgård ́s approach was evaluated as the most cost-effective air tightening and pressure testing method, see Table 13. Implications: The study shows that the air tightening methods of both objects work to reach the building's airtightness requirements. As the methods were similar at many points, it could be concluded that the air tightening of window- and door connections had a major impact on time as well as the cost. Finally, the following recommendations that can be given is, building airtightness should be ensured at an early stage, companies' air tightening and pressure testing methods should continue to evolve and a uniform air tightening and pressure testing method should be designed and applied throughout the companies. Limitations: The report's investigation strategy is a quantitative case study. The study is limited to two study objects of the case study and their air tightening and pressure testing method without regard to material costs. The investigation is also limited to the object's conditions as material choice, but does not consider geographical location or weather-orientation. This means that the study is valid under specific conditions. In the event of a repeat, the study can demonstrate other results and generate different conclusions than those undertaken in this investigation.
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Seidel, Robin. "Mechanical dynamic response of airflow sensors of airflow sensors of crickets." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493806.
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Insects have evolved very elaborate sensing systems. The airflow sensors of crickets are among the most sensitive sensors in the animal world. The sensor comprises a thin hair, which protrudes from the surface of the cuticle and sits in a specialised socket. Its elliptical base is surrounded by a flexible joint membrane to allow the hair to rotate. The polarity of the base restricts the rotation of the hair to a preferred plane of movement. The results of the morphometric analysis of the airflow sensors presented in this study show that the maximal diameter of the hair is a strong predictor for the other parameters determining the sensors geometry, such as the hair length, its socket geometry, as well as the hair's elliptical base, which is otherwise hidden within the socket and out of view unless the hair and its base are removed.
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Solaymani-Kohal, Jamshid. "Airflow through horizontal openings." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294525.
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Jaroslawski, ML. "Airflow limitation in croup." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/26628.
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This thesis investigates a mechanism for air flow limitation in children with croup. Croup is a common condition affecting many young children. Infection (usually viral) causes swelling of the mucosa in the subglottic region of the airway with consequent narrowing of the airway. Although researchers have investigated croup for the past sixty years, there is still very little information available on how croup affects air flow dynamics. The current theory assumes that the stenosis formed by croup in the subglottis of infants leads to a dynamic collapse of the extrathoracic trachea (Chernick, 1990). According to this literature, the dynamic collapse of the extrathoracic trachea will limit the inspiratory flow. It was believed that in severe cases of croup, the dynamic collapse may even temporarily block the airways. In order to investigate the mechanism for air flow limitation in croup the author used the intrathoracic pressure - flow traces from twenty patients with croup, four patients who had been intubated for croup and five normal subjects. Laryngeal X-rays from another twenty patients with croup were analysed as well as five videos, made during laryngoscopy, of the subglottic cross-sectional area of an additional five patients with croup requiring intubation. All data used in this project was collected by an experienced paediatrician from the Red Cross War Memorial Children's Hospital who is also the supervisor of this thesis. Both the video and the X-ray data showed that the dynamic collapse of the trachea contributes much less to airflow obstruction than the subglottic swelling itself. The hypothesis investigated in this thesis is that air flow becomes restricted due to wave speed limitation. According to the theory of wave speed limitation, an increase in driving pressure (the intrathoracic pressure) does not increase the flow if the speed of the air particles exceeds the wave speed. In our case the wave speed is the speed of sound within the lumen of the compliant, narrowed airway. In order to test that theory, it was necessary to obtain the flow, the driving pressure in the subglottis and the cross-sectional area of the subglottis of patients with croup. Unfortunately, the measurement of subglottal cross-sectional areas from videos made during laryngoscopies, proved to be impossible due to both ethical and practical constraints. The measurement of the subglottal cross-sectional areas from X-rays was also difficult in practice. Therefore, the cross-sectional area is calculated. The general orifice equation is modified m order to calculate the subglottal cross-sectional areas in patients with croup. Two methods are used to test the hypothesis of wave speed limitation: i) The wave speed limitation formula. The wave speed limitation formula directly calculates the maximum flow from the pressure - flow data. Hereafter the calculated maximum flow is compared with the measured flow. ii) A lumped component model. A nonlinear, lumped component model has been used to calculate the flow from the driving pressure (intrathoracic pressure). Flow is not limited in this model and an increase in driving pressure will result in a corresponding increase in flow. The flow which is calculated using this model has also been compared to the measured flow. It was found that, in children with croup, there is a good correlation (r=0.82) between calculated and measured values of maximum flow using the wave speed limitation model. The slope of the linear fit using a least square's approximation is 0.98 and this linear relationship is valid for a 0.05 level of significance for Conover's nonparametric test (Daniel and Terrell, 1989). The lumped component model was able to fit the inspiratory flow data with a small sum of square error in the case of both normal ((7.56 ± 0.86) · 10⁻⁹ (ml/s)²) and intubated patients ((3.2 ± 0.75)·10⁻⁹ (ml/s)²). However, the error rose dramatically in patients with croup ((2.04 ± 0.5) -10⁻⁸ (ml/s)²) thus indicating that the lumped component model is no longer valid in these patients. It is concluded that the measured flow velocities in patients with croup approach the calculated velocity of sound in the region of the subglottic swelling, and that the wave speed theory accurately describes the flow limitation. Further support of this is the fact that the lumped component model, which does not incorporate a flow limiting mechanism, breaks down in patients with croup.
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Abedi, Milad. "Directional Airflow for HVAC Systems." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/88524.
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Directional airflow has been utilized to enable targeted air conditioning in cars and airplanes for many years, where the occupants could adjust the direction of flow. In the building sector however, HVAC systems are usually equipped with stationary diffusors that can only supply the air either in the form of diffusion or with fixed direction to the room in which they have been installed. In the present thesis, the possibility of adopting directional airflow in lieu of the conventional uniform diffusors has been investigated. The potential benefits of such a modification in control capabilities of the HVAC system in terms of improvements in the overall occupant thermal comfort and energy consumption of the HVAC system have been investigated via a simulation study and an experimental study. In the simulation study, an average of 59% per cycle reduction was achieved in the energy consumption. The reduction in the required duration of airflow (proportional to energy consumption) in the experimental study was 64% per cycle. The feasibility of autonomous control of the directional airflow, has been studied in a simulation experiment by utilizing the Reinforcement Learning algorithm which is an artificial intelligence approach that facilitates autonomous control in unknown environments. In order to demonstrate the feasibility of enabling the existing HVAC systems to control the direction of airflow, a device (called active diffusor) was designed and prototyped. The active diffusor successfully replaced the existing uniform diffusor and was able to effectively target the occupant positions by accurately directing the airflow jet to the desired positions.M.S.
The notion of adjustable direction of airflow has been used in the car industry and airplanes for decades, enabling the users to manually adjust the direction of airflow to their satisfaction. However, in the building the introduction of the incoming airflow to the environment of the room is achieved either by non-adjustable uniform diffusors, aiming to condition the air in the environment in a homogeneous manner. In the present thesis, the possibility of adopting directional airflow in place of the conventional uniform diffusors has been investigated. The potential benefits of such a modification in control capabilities of the HVAC system in terms of improvements in the overall occupant thermal comfort and energy consumption of the HVAC system have been investigated via a simulation study and an experimental study. In the simulation study, an average of 59% per cycle reduction was achieved in the energy consumption. The reduction in the required duration of airflow (proportional to energy consumption) in the experimental study was 64% per cycle on average. The feasibility of autonomous control of the directional airflow, has been studied in a simulation experiment by utilizing the Reinforcement Learning algorithm which is an artificial intelligence approach that facilitates autonomous control in unknown environments. In order to demonstrate the feasibility of enabling the existing HVAC systems to control the direction of airflow, a device (called active diffusor) was designed and prototyped. The active diffusor successfully replaced the existing uniform diffusor and was able to effectively target the occupant positions by accurately directing the airflow jet to the desired positions.
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Fung, Chak Fai. "The structure of airflow over waves." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409924.
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Rennie, Catherine. "Investigation of sinonasal airflow and transport." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23889.
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This work comprises an investigation of airflow and transport in the human upper airways, which not only perform essential air conditioning physiological functions (heat and water exchange and primary filtration) but also house the olfactory receptors. The conflicting requirements posed by efficient air transit on the one hand and sampling for olfaction on the other renders the geometry of the upper airways complex. Knowledge of the geometry and flow conditions are primary requirements for understanding the physiological mechanics of the airways. This work describes the application of imaging and experimental measurement techniques to determine the variations in nasal airway geometry and the characteristics of nasal inspiratory flow. Whilst the results are relevant to a host of applications, the particular case of sinonasal ventilation well illustrates the interrelation between form, flow and function as well as motivating the development of improved techniques for clinical management. Specifically 3T MR imaging has been investigated as a means to define the anatomy in congested and decongested states. Results show very large changes in nasal airway calibre and moreover allow the variation in mucosal engorgement throughout the nasal cavity to be mapped. Highly time resolved hot wire measurements of inspiratory flow profiles revealed for the first time the rapid temporal development of inspiratory flow during normal inspiration and dramatically so during sniffing. Variations in flow profile were recorded across a cohort of subjects for conditions of normal inspiration, sniffing and smelling. Sinonasal gas exchange is of particular interest given the common occurrence of sinus pathologies. Here short half-life Krypton imaging has been used to investigate gas exchange between the maxillary sinus and the nasal cavity. It has been shown that the technique can provide quantitative assessment of volume flow rate in a model, demonstrating the rapid venting associated with an accessory ostium.
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Baddock, Matthew. "Airflow dynamics in transverse dune interdunes." Thesis, University of Northampton, 2005. http://nectar.northampton.ac.uk/2994/.
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Aeolian dune interdunes have been relatively ignored when compared with the research attention on the morphodynamics of the dune bodies themselves. This neglect is in spite of the possible significance of interdune dynamics for the geomorphology of the sand dune system as a whole, especially with regard to dune spacing. This project involved the collection of geomorphologically relevant airflow data for four relatively simple transverse dune interdunes. The study locations were chosen in order to sample interdunes with different size and surface type characteristics, the dynamics of which were investigated for when incident flow was normal to the upwind crest. The findings confirm existing models of aeolian dune lee-side flow in terms of flow re-attachment length and recovery attributes. A consistent pattern of increasing near-surface velocity downwind of re-attachment provides a mechanism for interdunes as sand-free features. Where studies for comparison from other aeolian examples are limited, the field-measured turbulence shows the importance of the shear layer as a source of turbulence, and agrees with studies from subaqueous bedforms. The importance of shear stress variability and the possible contribution of turbulence structures to the maintenance of sediment transport at re-attachment where velocity and mean stress is low or negative is also emphasised. At the downwind edge of interdunes, the mean and turbulent velocity properties, and therefore morphodynamics, vary according to the interdune size. In this case, interdune length leads to greater recovery, and a balance exists in this region between the recovering flow at the surface, dissipating wake from above and the obstacle effect of the dune. The flow dynamics are characterised for the different types of interdune observed. Dynamics accordant with the flow response model are seen to characterise the interdune setting with the closest spacing. The occurrence of other “extended” aeolian interdunes with a length well over that for flow separation demanded the development of a new descriptive model to characterise the dynamics therein. In this model, the variation in near-surface flow allowed process zones to be identified through the interdune. The geomorphological significance of the processes dominating each zone are discussed and comparisons are made between the flow response case and the new interdune model from this study
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Odewole, Gboyega Akindeji. "Airflow patterns in ventilated wall cavities." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/airflow-patterns-in-ventilated-wall-cavities(f67d5b52-af96-4784-a1ac-6d6c3c41812e).html.
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Though heating, insulation, wall claddings and cavity-wall construction are considered as measures for remediating moisture and condensation in buildings, ventilation of wall cavities has however become a mantra among architects and other building professionals. Holes of any size and shape are made and located on building facades based on the accepted wisdom that a little air movement will keep the wall cavities dry. Whilst ventilation has been found to be successful in the control of moisture and condensation in rooms and larger enclosures, there is however insufficient understanding of how it works in thin spaces with high aspect ratios, such as the wall cavities studied in this thesis.In order to put in place good control and management practices in the remediation of moisture and condensation in vertical wall cavities by natural ventilation, it is vital to understand the dynamics of airflow in these cavities. In this thesis therefore, different size and shape of slots were employed to numerically investigate the effects of size, spacing and number of the slots on the characteristics of the velocity fields (patterns of airflow and distributions of velocity) in different cavity models. The Reynolds-Averaged-Navier-Stokes (RANS) methodology was employed to simulate the cavity flows under different modelling conditions using FLUENT. The BS 5925 model, an empirical relation for predicting ventilation rates in rooms and other larger enclosures, was employed and modified to predict ventilation rates in these cavities. Experimentally, the mapping of the airstreams in these cavities was obtained under similar reference (inlet) wind speeds employed for the numerical investigations.The results of this study show that there exists a potential at higher wind speeds for natural ventilation in the remediation of moisture and condensation in the cavities of vertical walls. The steady state approach employed in the RANS-based computation of cavity flows in this thesis averages out the peak values of air velocities and therefore gives no information about regions of maxima or minima velocity values even at higher wind speeds. This makes the predicted air change rates insensitive to the inlet air velocities from the ventilation slots and therefore makes the results more applicable for long term control and management of moisture in these cavities. In order to therefore put in place short, medium and long term plans for remediation of moisture in these wall cavities, a time-dependent computation is required. This will also allow the efficiency of the cavity ventilation to be properly assessed. Using the modified BS 5925 model, reasonable predictions were obtained for the air change rates of the wall cavities with the different size of ventilation slots employed. Close agreements are also obtained at lower and higher wind speeds between the predicted ventilation rates from the modified BS 5925 model and the experimental results employed as benchmark for validating the results.
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Bates, Alister. "Mechanics of airflow in human inhalation." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25515.
Full textAbstract:
The mechanics of airflow in the large airways during inspiration affects important physiological functions such as ventilation, olfaction, heat exchange and mass transfer. The behaviour of the airflow is important not only for healthcare applications including diagnosis, intervention planning and assessment, but for inhalation toxicology. This research aims to further the understanding of human nasal physiology through computational modelling. Specifically, the effects of transient inhalation conditions on flow dynamics and transport were characterised and the changes in flow behaviour in response to certain pathologies quantified. The key findings can be summarised as follows: Firstly, the time scales for airflow in the large airways have been identified and the initial flow patterns revealed. Three phases in the temporal behaviour of the flow were identified (flow initiation, quasi-equilibrium and decay). The duration of each phase differs depending on the quantity of interest. Flow in the nose was characterised as transitional, whilst in parts of the descending airways it is turbulent, particularly in the faster moving regions around the jets which may occur in the pharynx, larynx and at the superior end of the trachea. The bulk of the flow is biased to fill only certain regions of the airways, whilst other regions carry little flow, due to features upstream. Analysis of cross-sectional images provided by medical imaging does not necessarily provide a representative view of the area available to the flow. Various scalar species were employed to represent the fate of nanoparticles and gaseous species within the airways. Only species with high diffusion rates exhibited significant absorption at the airway walls. Airway pathologies often cause changes to the geometry of the airway. One such pathology, the goitre, was found to curve the trachea and in some cases cause constriction. Both these geometric changes were found to increase the pressure loss and energy required to drive flow through the trachea. Furthermore, the flow in pathological cases was more disturbed. High resolution simulations have been used to address these topics and the scales simulated have been analysed in terms of the smallest features possible in the flow to determine their fidelity.
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Louka, Petroula. "Measurements of airflow in an urban environment." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312298.
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Tsui, Wing Shum. "Nasal geometry and airflow dynamic in Chinese /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-bc-b23750881f.pdf.
Full textAbstract:
Thesis (Ph.D.)--City University of Hong Kong, 2009."Submitted to Department of Building and Construction in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 217-263)
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Ray, Stephen D. (Stephen Douglas). "Modeling buoyancy-driven airflow in ventilation shafts." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74930.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 185-191).
Naturally ventilated buildings can significantly reduce the required energy for cooling and ventilating buildings by drawing in outdoor air using non-mechanical forces. Buoyancy-driven systems are common in naturally ventilated commercial buildings because of their reliable performance in multi-story buildings. Such systems rely on atria or ventilation shafts to provide a pathway for air to rise through the building. Although numerous modeling techniques are used to simulate naturally ventilated buildings, airflow network tools (AFNs) are most commonly used for annual simulations. These AFNs, however, assume minimal momentum within each zone, which is a reasonable approximation in large atria, but is inappropriate in smaller ventilation shafts. This thesis improves AFNs by accounting for momentum effects within ventilation shafts. These improvements are validated by Computation Fluid Dynamics (CFD) models that haven been validated by small scale and full scale experiments. The full scale experiment provides a detailed data set of an actual atrium that can be used in further validations and demonstrates the first use of a neutrally buoyant bubble generator for flow visualization and particle image velocimetry within a buoyancy driven naturally ventilated space. Small scale experiments and CFD simulations indicate an "ejector effect" within the shaft that uses momentum from lower floors to induce flow through upper floors. In some configurations, upper floors achieve higher flow rates than lower floors. Existing AFNs do not predict this "ejector effect" and are shown to significantly under predict flow rates through ventilation shafts by 30-40%. Momentum effects are accounted for in AFNs using empirical relationships for discharge coefficients. This approach maintains the current structure of AFNs while enhancing their ability to simulate airflow through ventilation shafts. These improvements are shown to account for the "ejector effect" and predict airflow rates that agree with CFD simulations to within 1-25%.
by Stephen Douglas Ray.
Ph.D.
25
Xu, Weiran 1968. "New turbulence models for indoor airflow simulation." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9933.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Includes bibliographical references (p. 157-165).
It is important to predict indoor environment in order to design thermally comfortable and healthy indoor spaces. Heating, Ventilating and Air Conditioning (HVAC) design engineers and architects widely use the Computational Fluid Dynamics (CFD) technique for indoor environment predictions. The CFD technique requires a turbulence model to correctly calculate indoor air distribution. However, the currently available turbulence models in the literature are either inaccurate or inefficient for the indoor environment predictions. To solve the problem, this thesis proposes two two-layer turbulence models and a zero-equation turbulence model. The two-layer models use a one-equation (k) model for the near wall region and the "standard" k -£ model in the outer region. The zero-equation model calculates turbulent viscosity based on local velocity and a length-scale. The near wall models have been developed with the aid of the data of natural and forced convection flows by Direct Numerical Simulation (DNS), while the zero-equation model has been proposed empirically. One of the two-layer turbulence models is used for predicting natural convection in rooms. The other two-layer model and the zero-equation model can be used to predict forced, natural, and mixed convection in rooms. These three new models have been applied to predict different types of indoor airflows. The corresponding DNS or experimental data were used to validate the models. This study concludes that the two-layer models can predict airflows most accurately, better than many k -E models. The computing cost is significantly lower than that of the low Reynolds number k-E models and is only slightly higher than that of the "standard" k-E models. The zero-equation model is at least ten times faster than the "standard" k-E model and it is numerically stable and can predict indoor airflow with acceptable accuracy.
by Weiran Xu.
Ph.D.
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Rowell, Jeffrey. "Schlieren imaging : visualization of airflow in speech." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55103.
Full textAbstract:
Schlieren imaging is a non-invasive research tool that enables real-time visualization of airflow through refraction of light. Used predominantly in aerospace and ballistics research, its suitability for observing airflow in speech was proposed nearly 40 years ago. To date, this potential has been virtually unexplored. The following proof-of-concept study investigates the visual correlates of nasal versus non-nasal airflow to provide a preliminary demonstration of the tool’s ability to visualize aerodynamic events in speech. Simultaneous schlieren and audio recordings were made of three French nasal/non-nasal minimal pairs spoken by eight native-French speakers. These stimuli were presented to 10 raters in Video-only, Audio-only and Combined Audio-Visual formats. The raters coded each stimulus as either “nasal” or “not nasal”. Accurate designation of Video-only stimuli was significantly above chance response (p < .05), indicating that the difference between airflow for nasal and non-nasal sounds can be visualized and perceived through schlieren imaging alone. Non-significant improvements were observed over time in the Video-only condition. Differences between Combined Audio-Visual and Audio-only stimuli were non-significant and likely influenced by a ceiling effect for the auditory information presented in both conditions. Further research is needed with more difficult auditory-perceptual tasks to explore potential supplementary advantages of schlieren visual feedback alongside auditory ratings of resonance. Future research may also benefit from improved training procedures for schlieren imaging. Nonetheless, schlieren imaging has promising potential for future implementation in both speech research and clinical applications, particularly for speech resonance disorders.Medicine, Faculty of
Audiology and Speech Sciences, School of
Graduate
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Aghil, Salah Salem. "Characterisation of the internal aerodynamics of passenger compartments." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366476.
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MacFarlane, Susan Theresa. "Investigation of airflow through a compost-based biofilter." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0007/NQ41222.pdf.
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Tura, R. "Heat transfer and airflow phenomena in multilouvred ducts." Thesis, Coventry University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374680.
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Chrystyn, H. "Pharmacodynamics of theophylline in irreversible chronic airflow obstruction." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379859.
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Hassan, Wajahat. "Airflow obstruction and bronchial reactivity in rheumatoid arthritis." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336812.
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Kurujareon, Jutarat. "Simulation of airflow in the human tracheobronchial network." Thesis, University of Hertfordshire, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391374.
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Ruse, Charlotte. "Genetic epidemiological studies of late onset airflow obstruction." Thesis, University of Leicester, 2003. http://hdl.handle.net/2381/29441.
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Corsello, Joseph William. "Laboratory simulation of subsurface airflow beneath a building." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90012.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 82-84).
Vapor intrusion is the vapor-phase migration of volatile organic compounds (VOCs) into buildings due to subsurface soil or groundwater contamination. Oxygen replenishment rates beneath a building are significant for quantifying potential contaminant degradation rates within the vadose zone. Additionally, the migration of VOC soil gas vapors into buildings is partly due to pressure differences between the building and the subsurface. This study addresses these issues through two laboratory scale experiments. The Wind Experiment quantifies oxygen replenishment rates as a function of above ground wind speed, while the Depressurization Experiment examines the flow rate of air into a model building as a function of decreased building pressure. For the Wind Experiment, tests were run for basement and slab-on-grade building configurations, as well as with and without a simulated sidewalk. Results show that increased above ground wind speed increases the oxygen replenishment rate and that the presence of a simulated sidewalk inhibits the oxygen replenishment rate. For the Depressurization Experiment, tests were again run for basement and slab-on-grade building configurations, as well as for two different foundation crack percentages. Results of the experiment indicate that increased building vacuum increases the flow rate of air into the building. In addition, basement configuration, increased foundation crack percentage, or some combination of the two results in increased airflow into the building. Additional research is needed for both experiments in order to obtain statistically significant results and resolve remaining uncertainties. Specific research needs include an improved wind source, additional monitoring locations, various sidewalk sizes and shapes, and different foundation crack configurations.
by Joseph William Corsello.
M. Eng.
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Chang, Jui-Chen 1978. "Effectiveness and performance of double-skin airflow facades." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9037.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.Includes bibliographical references (p. 47).
Double-skin airflow facades have been in use for several years in European countries. They have yet to be used in the United States. One factor is that there is a lack of a heat transfer model which can accurately predict facade performance. A model of performance has been developed by Daniel Arons. The goal of the work presented is to verify the model with experimentation on a small-scale facade. Sunlight was simulated with a 400 W metal halide High Intensity Discharge lamp. Outdoor summer conditions were simulated with a residential space heater. Two 1/8" thick panes of uncoated window glass, separated by 7", with 1" white aluminum blinds in the center, made up the facade structure. Air was driven through the channel at velocities up to 0.7 mis. The results of experimentation validate the model when no light is being projected on the facade. More work needs to be done to refine the model for cases where there is little or no airflow and also when light is shining on the facade. More specifically, the interaction between incident radiation and blinds should be refined. The greatest discrepancy between model and experiment occurs for the surface temperature of glass on the heated side.
by Jui-Chen Chang.
S.B.
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Black, Duncan Stuart. "The interaction between waves and an overlying airflow." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/37112.
Full textAbstract:
This dissertation examines the interaction between a series of progressive gravity waves and an overlying airflow. A critical review of the existing literature is made, from which it is concluded that although a large number of wind-wave interactions have been proposed, few have been verified experimentally. Furthermore, virtually no consideration has been given to the effect of the airflow on the underlying wave motion. A comprehensive experimental investigation of the interaction between wind and waves has therefore been undertaken. In respect of the airflow, a complete set of kinematics measurements, involving both horizontal and vertical velocity data, is presented. The mean, wave-induced and fluctuating velocities are presented in a wave-following frame of reference. The flow streamlines are deduced from the measured velocity data, and the structure of the airflow examined in detail. Analysis of the velocity profiles using boundary layer theory enables the effects of the flow structure identified above to be quantified and an assessment of the surfece stresses made. A corresponding set of kinematics measurements were undertaken in the underlying water flow. The wind-induced currents and wave kinematics are examined. Numerical models to predict the wave motion in combined wind-wave field are developed. The models incorporate the effects of a wind-induced current and the varying surface stresses, and allow the relative importance of each of these effects to be investigated. Furthermore, measurements of the water surface elevation are used to investigate the modification to the underlying long waves caused by the airflow, and the nature of the superposed wind-waves. The variation in the properties of the wind-generated waves with the phase of the long waves are also examined. Finally, the fundamental mechanisms of wind-wave interaction are considered, and the relative importance of the various mechanisms assessed. The implications for the oflfehore engineer, in terms of wind loading, gas ventilation and wave loading are outlined.
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Stoakes, Preston John. "Simulation of Airflow and Heat Transfer in Buildings." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/35690.
Full textAbstract:
Energy usage in buildings has become a major topic of research in the past decade, driven by the increased cost of energy. Designing buildings to use less energy has become more important, and the ability to analyze buildings before construction can save money in design changes. Computational fluid dynamics (CFD) has been explored as a means of analyzing energy usage and thermal comfort in buildings. Existing research has been focused on simple buildings without much application to real buildings. The current study attempts to expand the research to entire buildings by modeling two existing buildings designed for energy efficient heating and cooling. The first is the Viipuri Municipal Library (Russia) and the second is the Margaret Esherick House (PA). The commercial code FLUENT is used to perform simulations to study the effect of varying atmospheric conditions and configurations of openings. Three heating simulations for the library showed only small difference in results with atmospheric condition or configuration changes. A colder atmospheric temperature led to colder temperatures in parts of the building. Moving the inlet only slightly changed the temperatures in parts of the building. The cooling simulations for the library had more drastic changes in the openings. All three cases showed the building cooled quickly, but the velocity in the building was above recommended ranges given by ASHRAE Standard 55. Two cooling simulations on the Esherick house differed only by the addition of a solar heat load. The case with the solar heat load showed slightly higher temperatures and less mixing within the house. The final simulation modeled a fire in two fireplaces in the house and showed stratified air with large temperature gradients.Master of Science
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Ren, Zhengen. "Enhanced modelling of indoor air flows, temperatures, pollutant emission and dispersion by nesting sub-zones within a multizone model." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269182.
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Vlachos, Bill Vaseleos. "Effect of shear layer modelling on the simulated flow in a cavity." Thesis, University of Hertfordshire, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369760.
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Wakefield, Nigel Hugh. "Helicopter flight in the airwake of non-aviation ships." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326729.
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Mealing, B. E. "Flow in a forward swept centrifugal fan." Thesis, Cranfield University, 1988. http://dspace.lib.cranfield.ac.uk/handle/1826/10333.
Full textAbstract:
The
original objective of this work, to improve the
efficiency of a forward curved centrifugal fan, was
redirected to the urgent solution of a serious
impeller life problem arising under certain service
conditions.
Using a variety of experimental and theoretical
techniques the flow pattern within the blade passage
was analysed and the cause of the problem diagnosed.
A new impeller has been designed and has been found
to solve the service life problem while also yielding
an improvement in efficiency.
Because the project was carried out under the Total
Technology programme the scope was widened to include
consideration of the fan application in a suction
roadsweeper : as a result of the wider technical
and commercial investigation an opportunity has
been identified for a new product offering benefits
much
greater than those sought within the scope of
the
original objective.
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Yazdanpanah, Fahimeh. "Permeability of bulk wood pellets with respect to airflow." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/15231.
Full textAbstract:
Data on the resistance of wood pellets to air flow are required for the design and control of ventilation and drying of bulk pellets in storage. In this study, pressure drops versus air flows were measured for several sizes of wood pellets, with diameter of 6 mm and lengths varying from 4 to 34 mm. Air flow rates ranging from 0.014 to 0.80 m s⁻¹ were used in the experiment. The maximum pressure drop measured was 2550 Pa m⁻¹. Three predictive models - Shedd, Hukill-Ives, and Ergun equations that relate pressure drop to air flow in bulk granular materials were used to analyze the data. The Ergun equation was found to provide the best fit to the data. Aeration of bulk pellets in storage requires a low airflow. The airflow range used for low permeability tests was from 0.0002 to 0.0220 m s⁻¹. The corresponding measured pressure drop ranged from 0.18 to 8.30 Pa m⁻¹ for low permeability tests. Three models were investigated and compared for the low permeability data. The increase in moisture content over a wider range of
airflows (0.0042 to 0.7 148 m ⁻¹) showed a slight decrease in the resistance to airflow due to increased moisture content.
Broken and fines are produced when pellets are handled. The resistance to air flow for wood pellets was measured in the presence of fine materials. Fines were defined as broken pellets passed a 4 mm sieve. The average geometric diameter of the fines was 0.75 mm. The pressure drop for pellets mixed with fines ranged from (2.0 to 191.2 Pa m⁻¹) and (7.9 to 1779.0 Pa m⁻¹) for 1% and 20% fines content (mass basis) respectively. Coefficients of Hukill and Ives’ equation for pellets were estimated as a function of percent fines content.
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Smyth, Thomas Andrew George. "Airflow and sediment transport dynamics in coastal dune blowouts." Thesis, Ulster University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.646398.
Full textAbstract:
Blowouts are erosional depressions that occur on pre-existing vegetated sand deposits. Their morphodynamic behaviour can reflect changes in anthropogenic activity, climatic conditions and animal behaviour; however patterns of deflation are poorly understood as near-surface airflow is complex. Previous research has indicated that flow is topographically manipulated as it moves through the landform, causing steering, reversal and jetting of the airflow. However, empirical data on these effects have been limited due to inadequacies in anemometer and sediment trap deployments. As a consequence knowledge of flow behaviour inside blowouts is limited to crude conceptual approaches. This study used ultrasonic three-dimensional anemometry (50 Hz) to validate a three dimensional computational fluid dynamics (CFD) model. This enabled a detailed description and explanation of near surface wind flow within a bowl blowout from a variety of wind direction and wind speeds up to hurricane force. Three-dimensional anemometry complemented by a CFD simulation was used to quantify wind conditions, whilst high resolution (25 Hz) electronic load cell traps and saltation impact responders, measured sediment transport within a trough blowout. The results demonstrate that considerable flow streamline compression, expansion, steering and reversal occur within trough and saucer blowouts. Airflow within blowouts alters with incident wind direction but does not change structurally with wind speed. Sediment transport flux and intermittency vary considerably within the landform, whilst the best correlation between wind flow and sediment transport varies between wind speed and turbulent kinetic energy (TKE). Where wind speed correlates best with TKE, the optimum averaging interval is much lower than those locations which correlate best with wind speed.
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Moloney, Kenneth W. "An analysis of airflow patterns in auxiliary ventilated drivages." Thesis, University of Nottingham, 1997. http://eprints.nottingham.ac.uk/12364/.
Full textAbstract:
In recent years the drivage advance rates achieved within the UK coal industry have increased. In the 1980's average drivage rates were 35m per week compared to the 100/150m per week possible today. These extended rates of advance have resulted in an increase in the potential methane, dust and heat generation within the vicinity of the drivage face. In order to effectively disperse this additional pollutant load a controlled increase in air quantity is required. Although advance rates have changed, current auxiliary ventilation practice has not. UK mining law requires that the fresh air must be delivered to within 5m of the face. This has lead to the wide spread adoption of the use of overlap auxiliary systems within mechanised drivages, since a pure forcing system set at this distance from the face would lead to excessive airborne dust. UK mining law does not at present consider on-board mounted exhaust scrubber fans to constitute an effective overlap fan within mechanised drivages. Consequently an additional overlap exhaust fan is required to be installed within such drivages. In an attempt to determine whether working conditions could be safely and economically improved within mechanised rapid development drivages utilising an on-board mounted exhaust fan, a series of preliminary full scale gallery trials were conducted. A summary of the principal findings of these trials is presented together with an outline of a series of representative CFD simulations. This thesis examines the accuracy of CFD simulations for auxiliary ventilated headings. This is achieved by utilising Laser Doppler Anenometry (LDA) in a scale model representative of an underground heading and a detailed underground measurement programme conducted in production headings. These measured airflow values are then compared with representative CFD simulations and conclusions
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Lu, Weizhen. "Modelling of airflow and aerosol particle movement in buildings." Thesis, De Montfort University, 1995. http://hdl.handle.net/2086/4273.
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Al-Maskari, Juma. "Processes of convection and airflow over the Hajar Mountains." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432311.
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Church, Sally Georgina. "On the measurement of airflow obstruction in conscious man." Thesis, King's College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309143.
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Felgner, Felix. "Design of virtual airflow sensors for thermal comfort control." Aachen Shaker, 2008. http://d-nb.info/992052807/04.
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Landolt, Scott David. "An analysis of airflow patterns inside precipitation gauge shielding." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453573.
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Nayebossadri, Shahrzad. "Computational and experimental study of nasal cavity airflow dynamics." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8611.
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This work aims to assess human nasal blockage by investigating its influence on nasal airflow dynamics, both computationally and experimentally. An in-house CFD code (Lithium) computes the steady (mean) nasal airflow for a cavity constructed from CT images of a healthy adult, for the internal cavity and for the first time for the external flow. To account for turbulence occurrence, the low Reynolds number k-ω Reynolds-Averaged-Navier-Stokes (RANS) model is used. The flow field is calculated at different breathing rates by varying the influx rate. Blockages are introduced at various locations inside the cavity to investigate common nasal blockages. The computational results are assessed against published literature and the Particle Image Velocimetry experimental (PIV) results, carried out on a 2.54:1 scale model of the computational nasal cavity. Schlieren optical technique is also used for external nasal airflow visualizations of a human subject, to comment on using an optical system for clinical application. These computations reveal a significant dependency of both, the internal and external nasal airflow fields on the nasal cavity’s geometry. Although for this model, the flow is found to be turbulent in the inspiratory phase of 200 ml/s and higher, it is suggested that the nature of flow can vary depending on the nasal cavity’s structure which is influenced by genetics. Nevertheless, some common flow features were revealed such as higher flow rate in the olfactory region and main flow passage through lower airways during inspiration. More uniform flow passage was found in expiration. The results also suggest a possible correlation between the internal geometry of the cavity and the external nasal airflow angle and thickness. This correlation can allow an application of optical systems such as Schlieren which is shown to give accurate qualitative images of the external nasal airflow for assessment of the nasal blockage.