While tracking balloons for wind characterization, there was a question about the theoretical rise rate and corresponding coefficient of drag of a balloon shape as compared to a sphere. Since there are many studies published detailing the drag on spherical shapes, the question of whether or not a balloon can be treated as a sphere begged to be answered. In this study we apply Computational Fluid Dynamic (CFD) modeling to compare the aerodynamic behavior and drag of a sphere to that of a balloon as it moves through fluid at Reynolds numbers from 10,000 to 100,000. Fluent CFD models are created and used to estimate the coefficient of drag (Cd) vs. Reynolds number (Re) for a sphere and for a balloon shape. Details are given for the meshed model creation and the simulation methods. Sphere model results are compared to data provided in published literature. Sphere and balloon model results are compared to each other. The results of this study show that the drag on a balloon is not statistically different from a sphere. While there are differences in the flow characteristics over the two shapes, a spherical shape is a good approximation for a balloon shape.

<p>The main aim of the project is the creation of a CFD model for a plant in the Falun Hospital in Sweden. CFD is a new area of engineering that appears because of the great improvement in the computers last years. Creating a CFD model is a difficult process but the model is capable to give a great amount of data and also the model allows predicting the results when parameters of the system are changed so the model lets to save money and time and becomes an interesting tool to choose the optimal solution for the system.</p><p>In this case the system studied is the air distributed by the ventilation system inside a plant of the Falun Hospital. The model have to predict the characteristics of the airflows inside the plant, how the air moves through the different areas of the plant and how these airflows affects in the distribution of temperature inside the plant.</p><p>Also the model has to become a use tool to analyze possible changes in the ventilation system to improve it. And a tool to get boundary conditions to study specific areas of this zone in future studies.</p><p>The project its part of a bigger project performed by the department of energy technology from Gävle university “Consequences in comfort and inside environment at energy optimization within the health care sector”. The project it is a study of the use of energy in health care buildings in Sweden after the analysis of the energy usage a study to optimize the use of the energy and how these changes affects the patient and workers climate comfort in these buildings.</p><p>The CFD model have to be a tool that helps in the study of the ventilation system and the relation with the comfort in the Falun Hospital and also a tool to choose an optimal solution for the ventilation system after changes to improve the energy usage in the building avoiding the use of experimental changes in the hospital.</p>

Chosen as one of six Generation‒IV nuclear-reactor concepts, SuperCritical Water-cooled Reactors (SCWRs) are expected to have high thermal efficiencies within the range of 45 ‒ 50% owing to the reactor‟s high pressures and outlet temperatures. The behaviour of supercritical water however, is not well understood and most of the methods available to predict the effects of the heat transfer phenomena within the pseudocritical region are based on empirical one-directional correlations which do not capture the multi-dimensional effects and do not provide accurate results in regions such as the deteriorated heat transfer regime. Computational Fluid Dynamics (CFD) is a numerical approach to model fluids in multidimensional space using the Navier-Stokes equations and databases of fluid properties to arrive at a full simulation of a fluid dynamics and heat transfer system. In this work, the CFD code, FLUENT-12, is used with associated software such as Gambit and NIST REFPROP to predict the Heat Transfer Coefficients at the wall and corresponding wall temperature profiles inside vertical bare tubes with SuperCritical Water (SCW) as the cooling medium. The numerical results are compared with experimental data and 1-D models represented by existing empirical correlations. Analysis of the individual heat-transfer regimes is conducted using an axisymmetric 2-D model of tubes of various lengths and composed of different nodes count along the heated length. Wall temperatures and heat transfer coefficients were analyzed to select the best model for each region (below, at and above the pseudocritical region). To neutralize effects of the rest of the tube on that region, smaller meshes were used were possible. Two turbulent models were used in the process: k-ε and k-ω, with many variations in the sub-model parameters such as viscous heating, thermal effects, and low-Reynolds number correction. Results of the analysis show a fit of ±10% for the wall temperatures using the SST k-ω model in the deteriorated heat transfer regime and less than ±5% for the normal heat transfer regime. The accuracy of the model is higher than any empirical correlation tested in the mentioned regimes, and provides additional information about the multidimensional effects between the bulk-fluid and wall temperatures. Despite the improved prediction capability, the numerical solutions indicate that further work is necessary. Each region has a different numerical model and the CFD code cannot cover the entire range in one comprehensive model. Additionally, some of the trends and transitions predicted are difficult to accept as representation of the true physics of SCW flow conditions. While CFD can be used to develop preliminary design solutions for SCW type reactors, a significant effort in experimental work to measure the actual phenomena is important to make further advancements in CFD based analysis of SCW fluid behaviour. / UOIT

When thinking of renovating the windows of old buildings, the building owner has a lot of decisions to make. These are to keep the window but make it more energy efficient by adding an extra pane or to completely change the whole window. At the same time, the joint between the window frame and wall makes a thermal bridge which depends on how much insulation has been placed in the cavities after installation. Upon the decision of keeping the window, the status of this joint will be unchanged. This thesis deals with finding out the best economical solution for a company that has rental apartments in Gävle in Sweden, Gavlegårdarna AB. To calculate the thermal bridges, which are weak areas of the building envelope in which they significantly increase the energy load of houses, a CDF program called Fluent is used to quantify the heat loss at the joints. Measurements have been performed to validate the CFD model. To simulate the energy savings in the building, the building energy simulation program IDA-ICE is used. Finally, Life Cycle Costing calculations are made to assess the best long term economical option. It is concluded that the most reasonable solution is to add an extra glass in the existing window, but it is not the most ecofriendly. A more ecological solution is to add the extra glass and to perform enhanced insulation at the joints around the window frames and walls, or to replace the old window with a new low energy window – however, these are not profitable so

Film cooling computations and experiments were performed to study heat transfer and adiabatic effectiveness for several geometries. Various assumptions commonly made in film cooling experiments were computationally simulated to test the validity of using these assumptions to predict the heat flux into conducting walls. The validity of these assumptions was examined via computational simulations of film cooling on adiabatic, heated, and conducting flat plates using the commercial code FLUENT. The assumptions were found to be reasonable overall, but certain regions in the domain suffered from poor predictions. Film cooling adiabatic effectiveness and heat transfer coefficients for axial holes embedded in a 1 [hole diameter] transverse trench on the suction side of a simulated turbine vane were experimentally investigated as well to determine the net heat flux reduction. Heat transfer coefficients were determined with and without upstream heating both with and without a tripped boundary layer approach flow. The net heat flux reduction for the trench was found to be much higher than for the baseline row of holes. Two transverse trench geometries and a baseline row of holes geometry were also simulated using FLUENT and the results were compared to experiments by Waye and Bogard (2006). Trends between simulated trench configurations and baseline cylindrical holes without a trench were found to be largely in agreement with experimental trends, suggesting that FLUENT can be used as a tool for studying new trench configurations. / text

The main aim of the project is the creation of a CFD model for a plant in the Falun Hospital in Sweden. CFD is a new area of engineering that appears because of the great improvement in the computers last years. Creating a CFD model is a difficult process but the model is capable to give a great amount of data and also the model allows predicting the results when parameters of the system are changed so the model lets to save money and time and becomes an interesting tool to choose the optimal solution for the system. In this case the system studied is the air distributed by the ventilation system inside a plant of the Falun Hospital. The model have to predict the characteristics of the airflows inside the plant, how the air moves through the different areas of the plant and how these airflows affects in the distribution of temperature inside the plant. Also the model has to become a use tool to analyze possible changes in the ventilation system to improve it. And a tool to get boundary conditions to study specific areas of this zone in future studies. The project its part of a bigger project performed by the department of energy technology from Gävle university “Consequences in comfort and inside environment at energy optimization within the health care sector”. The project it is a study of the use of energy in health care buildings in Sweden after the analysis of the energy usage a study to optimize the use of the energy and how these changes affects the patient and workers climate comfort in these buildings. The CFD model have to be a tool that helps in the study of the ventilation system and the relation with the comfort in the Falun Hospital and also a tool to choose an optimal solution for the ventilation system after changes to improve the energy usage in the building avoiding the use of experimental changes in the hospital.

Three-dimensional urban wind field construction plays an important role not only in the analysis of pedestrian levels of comfort but also in the effectiveness of harnessing wind energy in an urban environment. However, it is challenging to accurately simulate urban wind flow due to the complex land use in urban environments. In this study, a three-dimensional numerical model was developed for urban wind flow construction. To obtain an accurate urban wind field, various turbulence models, including the Reynolds Stress Model (RSM), Shear-Stress Transport (SST) k-ω, realizable k-ε, and Re-Normalization Group (RNG) k-ε models were tested. Simulation results were compared with experimental data in the literature. The RSM model showed promising potential in simulating urban wind flow. The model was then adopted to simulate urban wind flow for Purdue University Northwest, which is located in the Northwest Indiana urban region. Based on the simulation results, the optimal location was identified for urban wind turbine siting and the wind comfort was analyzed in the walk sides between the buildings.

This study investigates pause duration between and within utterances in the speech of 20 people with different degrees and types of aphasia: 15 with fluent aphasia and five with nonfluent aphasia. It also examines within utterance pause durations as a function of utterance position. Using aphasia speech samples collected in a previous study by Harmon (2018), Praat acoustic analysis software was used to segment words and periods of pause and measure pause duration within and between utterances. The data were analyzed using descriptive statistics, including pause duration mean, standard deviations, and interquartile range. Speech pauses were also categorized by the percentage of pause durations greater than 250 ms, 500 ms, 750 ms, and one second. Nonfluent aphasia presents higher mean durations of both between and within utterance pauses than fluent aphasia. Speakers with fluent and nonfluent aphasia subtypes exhibit a larger proportion of pauses longer than one second between utterances than within them. Between utterances, there is a positive association between increase in aphasia severity and an increase in pause duration. Within utterances, speech from individuals with moderately severe aphasia have longer mean pause durations than mild or very mild cases. Individuals with both fluent and nonfluent aphasia demonstrate increased pause durations in the initial sentence position. Further research will provide insight into how this compares with typical speech and how these pause patterns affect the communicative effectiveness of the speaker.

This work is done as a small facet of a much larger study on efficient control of indoor air environments. Halton passive chilled beams are used to cool rooms and the focus of this work is to model the beams. This work also reviews the mesh making process in Gmsh. ANSYS Fluent was used throughout the entire research and this thesis describes the software and a careful description of the case study. / Master of Science

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