Large Eddy Simulation (LES) is a relatively more accurate and reliable alternative to solution of Reynolds Averaged Navier Stokes (RANS) equations in simulating complex turbulent flows at a lesser computational cost than a direct numerical simulation (DNS). However, LES of wall-bounded flows still requires a very high grid resolution in the inner wall layer making its widespread use difficult. Different attempts have been made in the past time to overcome this problem by modeling the near wall turbulence instead of resolving it. One such approach is a two-layer wall model that solves for a reduced one-dimensional equation in the inner wall layer, while solving for the filtered Navier-Stokes equations in the outer layer. The use of such a model allows for a coarser grid resolution than a wall resolved LES. This work validates the performance of a two-layer wall model developed for an arbitrary body fitted non-orthogonal grid in the flow over a wall mounted hump at Reynolds number 9.36x105. The wall modeled large eddy simulation (WMLES) relaxes the grid requirement compared to a wall resolved LES (WRLES) by allowing the first off-wall grid point to be placed at a y+ of approximately 20-40. It is found that the WMLES results are general good agreement with WRLES and experiments. Surface pressure coefficient, skin friction, mean velocity profiles, and the reattachment location compare very well with experiment. The WMLES and WRLES exhibit some under prediction of the peak values in the turbulent quantities close to the reattachment location, with better agreement with the experiment in the separated region. In contrast, a simulation that did not employ the wall model on the grid used for WMLES failed to predict flow separation and showed large discrepancies with the experimental data. In addition to the relaxation of the grid requirement in the wall normal direction, it was also observed that the wall model allowed a reduction in the number of computational cells in the span-wise direction by half. However an LES calculation on a grid with reduced number of cells in span-wise direction turned unstable almost immediately, thereby highlighting the effectiveness of the wall model. Besides reducing the number of grid points in the spatial domain, the relaxed grid resolution for the WMLES also permitted the use of a larger time step. This resulted in an order of magnitude reduction in the total CPU time relative to WRLES. / Master of Science

Accelerometer data can be analyzed using a variety of methods which are effective in the clinical setting. Time-series analysis is used to analyze spatiotemporal variables in various populations. More recently, investigators have focused on gait complexity and the structure of spatiotemporal variations during walking and running. This study evaluated the use of time-series analyses to determine gait parameters during running. Subjects were college-age female soccer players. Accelerometer data were collected using GPS-embedded trunk-mounted accelerometers. Customized Matlab® programs were developed that included Gaussian continuous wavelet transform (CWT) to determine spatiotemporal characteristics, detrended fluctuation analysis (DFA) to examine gait complexity and autocorrelation analyses (ACF) to assess gait regularity. Reliability was examined using repeated running efforts and intraclass correlation. Proof of concept was determined by examining differences in each variable between various running speeds. Applicability was established by examining gait before and after fatiguing activity. The results showed most variables had excellent reliability. Test-retest R2 values for these variables ranged from 0.8 to 1.0. Low reliability was seen in bilateral comparisons of gait symmetry. Increases in running speed resulted in expected changes in spatiotemporal and acceleration variables. Fatiguing exercise had minimal effects on spatiotemporal variables but resulted in noticeable declines in complexity. This investigation shows that GPS-embedded trunk-mounted accelerometers can be effectively used to assess running gait. CWT and DFA yield reliable measures of spatiotemporal characteristics of gait and gait complexity. The effects of running speed and fatigue on these variables provides proof of concepts and applicability for this analytical approach. / Master of Science / Fitness trackers have become widely accessible and easy to use. So much so that athletic teams have been using them to track activity throughout the season. Researchers are able to manipulate data generated from the fitness monitors to assess many different variables including gait. Monitoring gait may generate important information about the condition of the individual. As a person fatigues, running form is theorized to breakdown, which increases injury risk. Therefore the ability to monitor gait may be advantageous in preventing injury. The purpose of this study is to show that the methods in this study are reproducible, respond reasonably to changes in speed, and to observe the changes of gait in the presence of fatigue or on tired legs. Three analyses are used in this study. The first method called autocorrelation, overlays acceleration signals of consecutive foot strikes, and determines the similarity between them. The second method utilizes a wave transformation technique that is able to determine foot contact times. The final method attempts to determine any pattern in the running stride. This method looks for changes in the structure of the pattern. Less structure would indicate a stride that is fatigued. The results showed that the methods of gait analysis used in this study were reproducible and responded appropriately with changes in speed. Small changes in gait were observed due to the presence of fatigue. Further investigation into the use of these methods to determine changes in gait due to the presence of fatigue are warranted.

Despite the potential of immersive virtual environments (VEs) as educational tools, little is known about how VE system parameters impact a child using the environment. Designers of VE applications targeted at children must rely on studies done with adults to guide their design decisions. The failure to understand how children differ from adults in their responses to VEs poses a serious obstacle to the design of effective learning environments for children. The main goal of this research was to quantify the impact of varying one VE system parameter, field-of-view, on large-scale, spatial learning in middle elementary schoolchildren and the incidence of side-effects in that population in an immersive VE. The other goals of this research were to identify 1) how, and if, middle elementary schoolchildren's responses to this environment differ from that of adult participants, and 2) how, and if, gender changed participant performance and responses. Adults and 7-9 year old children were taught a U-shaped route through a six room virtual house, while wearing a helmet mounted display (HMD). Participants viewed the environment under monoscopic conditions with the horizontal field-of-view (HFOV) of the display set at either 30 or 48 degrees. Head tracking was not enabled as the children were unable to maintain a normal head position while wearing the HMD. After the learning period, participants performed tasks designed to assess spatial knowledge of the space: 1) locomotion efficiency was measured by the number of collisions with objects, 2) landmark knowledge was measured by the participant's ability to recognize photos of objects found in the environment 3) route knowledge was measured by the participant's ability to correctly re-trace the route and name the sequence of landmarks along the route, 4) configuration knowledge was measured by the participant's ability to point to occluded landmarks, make spatial inferences, and construct a model of the environment. Participants also completed a simple questionnaire which assessed the incidence of equipment difficulties and side-effects, general enjoyment, and the sense of presence in the VE. Additionally, the participant's vision and balance was checked before and after immersion in the VE. Locomotion, route knowledge, and configuration knowledge efficiency increased significantly with both age and FOV. At the smaller FOV, both adults and 7-9 year olds developed a significantly lesser degree of spatial knowledge, with the effect being amplified in the 7-9 year olds. In general, the more sophisticated the level the spatial knowledge required by a task, the greater the impact of FOV and age, with configuration knowledge being achieved significantly less frequently than route knowledge. Gender also significantly impacted the development of configuration knowledge. Only landmark knowledge did not change with age, FOV, or gender. Also, the incidence of VE balance side-effects decreased significantly with age and was impacted by gender. The incidence of equipment difficulties also decreased with age,with significantly more, and longer, breaks being taken by 7-9 year olds than by adults. Further, general enjoyment of VE immersion and presence decreased significantly with age. / Master of Science

Small wind turbines, and especially urban-mounted turbines which require no dedicated pole, have garnered great public enthusiasm in recent years. This enthusiasm has fueled widespread growth among energy conservationists, and estimates predict that the power produced nationally by small wind will increase thirty-fold by 2013. Unfortunately, most of the wind resources currently available have been designed for larger, rural-mounted turbines; thus, they are not well suited for this nascent market. A consequence of this is that many potential urban small wind turbine owners over-predict their local wind resource, which is both costly and inefficient. According to a recent study published by Encraft Ltd., small wind turbines mounted to buildings far underperformed their rural pole mounted counterparts. As a proposed solution to this problem, this project introduces the concept of a Web-based Wind Assessment System (WWAS). This system combines all the necessary resources for potential urban small wind turbine customers into a single web-based tool. The system also presents the concept of a modular wind measurement system, which couples with the WWAS to provide real-time wind data measurements. The benefits of the system include its ease of use, flexibility of installation, data accessibility from any web browser, and expert advice. The WWAS prevents potential clients from investing in a system that may not be viable for their location. In addition, a small wind turbine is designed in this project, which has a unique modular mounting system, allowing the same baseline wind turbine to attach to various structures using interchangeable mounting hardware. This includes such accessible urban structures as street lights, building corners, flag poles, and building walls, among others. This design also utilizes concepts that address some of the challenges associated with mounting small wind turbines to existing urban structures. These concepts include: swept tip blades and lower RPM to reduce noise; vibration suppression using rubber shims; a netted duct to protect wildlife; and a direct-drive permanent magnet generator to ensure low starting torque. Finally, the cost of this system is calculated using off-the-shelf components, which minimize testing and certification expense. This small wind turbine system is designed to be grid-connected, has a 6 foot diameter rotor, and is rated at 1 kW. This design features a unique modular interchangeable mounting system. The cost for this complete system is estimated to be $2,050. If a users' site has an average wind speed of 14 mph (6.5 m/s), this system will generate a return on investment in 8.5 years, leaving over 10 years of profit. The profit for this system, at this sample average wind speed, yields over $4,000 during its 20-year design life, which is a two-fold return on investment. This project has implications for various stakeholders in the small wind turbine market, including designers, engineers, manufacturers, and potential customers. Equally important is its potential role in guiding our future national--even global--energy agenda.

<p>Train transportation is a vital part of the transportation system of today anddue to its safe and environmental friendly concept it will be even more impor-tant in the future. The speeds of trains have increased continuously and withhigher speeds the aerodynamic effects become even more important. One aero-dynamic effect that is of vital importance for passengers’ and track workers’safety is slipstream, i.e. the flow that is dragged by the train. Earlier ex-perimental studies have found that for high-speed passenger trains the largestslipstream velocities occur in the wake. Therefore the work in this thesis isdevoted to wake flows. First a test case, a surface-mounted cube, is simulatedto test the analysis methodology that is later applied to a train geometry, theAerodynamic Train Model (ATM). Results on both geometries are comparedwith other studies, which are either numerical or experimental. The comparisonfor the cube between simulated results and other studies is satisfactory, whiledue to a trip wire in the experiment the results for the ATM do not match.The computed flow fields are used to compute the POD and Koopman modes.For the cube this is done in two regions of the flow, one to compare with a priorpublished study Manhart & Wengle (1993) and another covering more of theflow and especially the wake of the cube. For the ATM, a region containing theimportant flow structures is identified in the wake, by looking at instantaneousand fluctuating velocities. To ensure converged POD modes two methods toinvestigate the convergence are proposed, tested and applied. Analysis of themodes enables the identification of the important flow structures. The flowtopologies of the two geometries are very different and the flow structures arealso different, but the same methodology can be applied in both cases. For thesurface-mounted cube, three groups of flow structures are found. First groupis the mean flow and then two kinds of perturbations around the mean flow.The first perturbation is at the edge of the wake, relating to the shear layerbetween the free stream and the disturbed flow. The second perturbation isinside the wake and is the convection of vortices. These groups would then betypical of the separation bubble that exists in the wake of the cube. For theATM the main flow topology consists of two counter rotating vortices. Thiscan be seen in the decomposed modes, which, except for the mean flow, almostonly contain flow structures relating to these vortices.</p> / QC 20100518 / Gröna Tåget

Year after year, technologies are evolving in an incredible rapid pace, becoming faster, more complex, more accurate and more immersive. Looking back just a decade, especially interaction technologies have made a major leap. Just two years ago in 2013, after being researched for quite some time, the hype around virtual reality (VR) arouse renewed enthusiasm, finally reaching mainstream attention as the so called head-mounted displays (HMD), devices worn on the head  to grant a visual peek into the virtual world, gain more and more acceptance with the end-user. Currently, humans interact with computers in a very counter-intuitive two dimensional way. The ability to experience digital content in the humans most natural manner, by simply looking around and perceiving information from their surroundings, has the potential to be a major game changer in how we perceive and eventually interact with digital information. However, this confronts designers and developers with new challenges of how to apply these exciting technologies, supporting interaction mechanisms to naturally explore digital information in the virtual world, ultimately overcoming real world boundaries. Within the virtual world, the only limit is our imagination. This thesis investigates an approach of how to naturally interact and explore information based on open data within an immersive virtual reality environment using a head-mounted display and vision-based motion controls. For this purpose, an immersive VR application visualizing information as a network of European capital cities has been implemented, offering interaction through gesture input. The application lays a major focus on the exploration of the generated network and the consumption of the displayed information. While the conducted user interaction study with eleven participants investigated their acceptance of the developed prototype, estimating their workload and examining their explorative behaviour, the additional dialog with five experts in the form of explorative discussions provided further feedback towards the prototype’s design and concept. The results indicate the participants’ enthusiasm and excitement towards the novelty and intuitiveness of exploring information in a less traditional way than before, while challenging them with the applied interface and interaction design in a positive manner. The design and concept were also accepted through the experts, valuing the idea and implementation. They provided constructive feedback towards the visualization of the information as well as emphasising and encouraging to be even bolder, making more usage of the available 3D environment. Finally, the thesis discusses these findings and proposes recommendations for future work.

An experimental study was designed to investigate the effect of different parameters on the development and structure of turbulent 3D offset jets. The present investigation considered the effects of offset height ratio, expansion ratio, surface roughness and rib placement on the flow dynamics of a turbulent 3D offset jet. The velocity measurements were performed using an acoustic Doppler velocimetry (ADV) and particle image velocimetry (PIV). Measurements were conducted within the symmetry and lateral planes. For the PIV technique, the measurements in the symmetry and lateral planes were conducted over a streamwise range of 0 ≤ x/bo ≤ 80 and 12 ≤ x/bo ≤ 60, respectively (where bo is the nozzle height). Likewise, velocity measurements using the ADV technique were conducted over a range of 4 ≤ x/bo ≤ 45 in both the symmetry and lateral planes. The velocity measurements were analyzed using both one-point and multi-point statistics. The one-point statistics included profiles of the mean velocities, Reynolds stresses and some of the budget terms in the turbulent kinetic energy transport equation. The quadrant analysis technique was used to investigate the dominant events that contribute towards the Reynolds shear stress. The two-point correlation analysis was used to investigate how the turbulence quantities are correlated. Information obtained from the two-point correlation analysis was also used to investigate the inclination of vortical structures within the inner and outer shear layers of the 3D offset jet. The direction of the positive mean shear gradient played an active role in the inclination of these vortical structures within the inner and outer shear layers. The reattachment process resulted in the breakdown of these structures within the developing region. Similarly, various length scales were estimated from these structures. The proper orthogonal decomposition was used to examine the distribution of the turbulent kinetic energy within the offset jet flow. Also, the dynamic role of the large scale structures towards the turbulent intensities, turbulent kinetic energy and Reynolds shear stress was investigated. / October 2016

Visualisation of proposed plans and designs can be done with a number of differenttechniques within the field of architecture and urban planning. But which visualisationtechnique is best suited when presenting a design proposal at a public consultation? Is therea breaking point where the user can form a general understanding of the proposed designdepending on the degree of fidelity? To seek answers to these questions a qualitative studywas conducted where five different visualisation techniques were tested on ten users toassess their understanding of a proposed design. Our findings show that there is not asingle best visualisation technique for public consultation. Based on our results thepreferred alternative would be a combination of several techniques. We could also see thatthe general understanding of a space increased until a certain degree, and after that adeeper more detail oriented understanding was achieved.

Abstract Photovoltaic (PV) solar panels are solar energy collection systems with increasing terrestrial and roof applications reported worldwide. If the terrestrial mounting does not require specific wind resistance verifications, installing them on top of flat and gable roofs implies a drastic change of the roofing systems geometry, thus a re-evaluation of the wind-induced pressure is necessary. Among the roof top applications, provisions exist for the flat roofs mounted solar panels, however, design recommendations for wind-induced loadings on PV solar panels arrays flush-mounted on gable roofs are not fully developed in current wind loading standards (SEAOC PV2-2012) and building codes (ASCE 07, NBCC 2015), in spite of the numerous applications on residential and agricultural buildings, primarily due to the limited research investigating this topic. The current dissertation employs CFD k-ɛ and LE (Large Eddy) simulations for analyzing the effects of wind acting on solar panels flush-mounted on gable roofs, considering the influence of several parameters such as: the slope of the gable roof, the wind directions, the spaces between the adjacent solar panel arrays and the clearance between the roof surface and the solar panels. A comprehensive database of solar panels with different installation parameters subjected to wind speeds were developed under the current research project. The database includes detailed distribution of wind-induced pressure coefficients for the three parallel surfaces constituting the roof-solar panels systems: the top and bottom surfaces of the panels, and the roof surface under the panels, which represents a novel approach in investigating and clarifying the wind effects on solar panels. This approach also provides in detail the variation of the pressure coefficients on the three surfaces, due to the change of installation conditions (roof slope, arrays spacing, roof clearance) and wind parameters (wind speed and wind direction). As an original contribution to the existing knowledge, this thesis found that the installation of solar arrays on gable roofs, redistributes the wind-induced pressure on both sides of the roof windward and leeward, resulting in total horizontal wind-induced pressures on the entire roof lower than that registered on the corresponding roof without solar panels. In addition, dominant resultant pressure coefficients on solar panels concluded to be lower than for the roof without panels. When the roof clearance increases, total average pressure coefficients on the roof supporting the panels decreases on both, windward and leeward sides of the roof. Moreover, when the roof clearance increases, the pressures in the cavity decrease significantly on both windward and leeward sides of the roof, which could impact the requirements for installing and fixing such panels on gable roofs. For example, for 10” clearance the flush-mounted solar panels were subject to pressure instead of suction. Similarly, when panel array spacing increases, the magnitude of the net mean pressure coefficients on the roof surface under the solar panels further decreases for all wind directions investigated.

As Vibrações Induzidas por Escoamentos (VIEs) são dos problemas dinâmicos mais importantes no projeto de trocadores de calor de tipo carcaça e tubos. Esta interação fluido - estrutura pode gerar vibrações de grande amplitude dos tubos ou partes internas do equipamento, o que pode provocar o impacto entre componentes e até falha por fadiga. Várias bancadas experimentais têm sido construídas para o estudo desta interação fluido - estrutura, no entanto, alguns mecanismos de vibração, principalmente aqueles relacionados com escoamentos bifásicos, não são completamente compreendidos. Portanto, neste trabalho, o projeto de uma estrutura dinâmica para o estudo das vibrações induzidas por escoamento bifásico é apresentado. Esta estrutura é composta por um sistema de fios de aço tensionados que permitem que a primeira frequência de ressonância do tubo seja sintonizada. O tubo instrumentado foi instalado numa seção de testes de tubos rígidos em configuração triangular normal com uma razão de passo transversal e diâmetro de 1,26. Os resultados experimentais foram contrastados com uma modelagem teórica desenvolvida para esta estrutura dinâmica. Pôde-se verificar que a primeira frequência de ressonância e seu fator de amortecimento coincidem com os valores estimados pelo modelo, enquanto que a segunda frequência de ressonância apresenta valor teórico 6,6% maior do que o experimental. A seguir, um estudo experimental no ar foi desenvolvido para o reconhecimento dos modos de vibração e as frequências de ressonância da estrutura dinâmica. O fator de amortecimento no ar também foi estimado, o método de Kennedy - Pancu combinado com o algoritmo ERA foi usado para este fim. Assim que a primeira frequência de ressonância foi reconhecida e sintonizada, testes em escoamentos de água foram realizados. A influência da velocidade do escoamento monofásico de água na amplitude de vibração e nas características da Densidade Espectral (PSD) de aceleração foi analisada. Finalmente, testes em escoamento bifásico foram feitos, a sensibilidade do tubo ao escoamento bifásico fica evidente quando analisadas as amplitudes nas PSDs. Além disso, a influência da fração de vazio na amplitude de vibração e no fator de amortecimento foi revisada, no entanto, resultados de estudos anteriores não foram conferidos pelo alto amortecimento concentrado introduzido por alguns elementos construtivos utilizados. / Flow - Induced Vibration (FIV) is the most critical dynamic issue in the design of heat exchangers. This fluid - structure phenomenon may generate high amplitude vibration of tubes or structural parts, which may lead to impacts between internal components or even failure due to fatigue. Many test benches have been constructed to study this fluid - structure interactions, however, some vibration mechanisms, mostly those related to multiphase flow, are not yet fully understood. Therefore, in this work, the design of a dynamic structure for the study of multiphase flow induced vibration is presented. This structure is composed by a system of tensioned piano wires that allow the first natural frequency of the instrumented tube to be calibrated. The tube was installed in a rigid bundle configured in a normal triangular pattern with pitch-todiameter ratio of 1.26. Then, an experimental study in air environment was performed aiming at addressing the mode shapes and resonance frequencies of the dynamic structure. The damping ratio in air environment was also estimated, the Kennedy - Pancu method in combination with the Eigensystem Realization Algorithm have been used to that purpose. Experimental results in air were compared with a theoretical model. The first resonance frequency and its damping factor presented a good agreement with the model, while the second resonance frequency deviated some 6,6% from the predicted value. Tests in water and multiphase flow were also performed. The influence of water flow velocity on vibration amplitudes and on the Power Spectrum Densities (PSDs) has been analyzed. Finally, tests for two - phase water/air flow were carried out; the tube sensitivity to multiphase flow is evident when the vibration level in acceleration PSDs is by analyzed. Also, the influence of void fraction on vibration amplitude and damping ratio have been addressed, however, previous studies could not be validated due to the high damping introduced by some constructive elements of the structure.