The motion of bacteria in the environment is relevant to several fields. At very small scales and with simple helical shapes, we are able to describe experimentally and mathematically the motion of solid spirals falling freely within a liquid pool. Using these shapes we intend to mimic the motion of bacteria called Spirochetes. We seek to experimentally investigate the linear and the rotational motion of such shapes. A better understanding of the dynamics of this process will be practical not only on engineering and physics, but the bioscience and environmental as well. In the following pages, we explore the role of the shape on the motion of passive solid helixes in different liquids. We fabricate three solid helical shapes and drop them under gravity in water, glycerol and a mixture of 30% glycerol in water. That generated rotation due to helical angle in water. However, we observe the rotation disappear in glycerol. The movement of the solid helical shapes is imaged using a high-speed video camera. Then, the images are analyzed using the supplied software and a computer. Using these simultaneous measurements, we examine the terminal velocity of solid helical shapes. Using this information we computed the drag coefficient and the drag force. We obtain the helical angular velocity and the torque applied to the solid. The results of this study will allow us to more accurately predict the motion of solid helical shape. This analysis will also shed light onto biological questions of bacteria movement.

Magnetotactic bacteria (MTB) possess organelles called magnetosomes which contain magnetite (Fe_3O_4) or greigite (Fe_3S_4) nanocrystals. These particles generate a magnetic moment allowing the use of external magnetic fields to control the cell orientation. MTB use this magnetic moment to reach environments with optimal oxygen concentration, a process called magnetotaxis. There are many possible technological applications for MTB, for example, they have been used as nanorobots to push beads and they can be used to remove heavy metals and radionuclides from waste water. In order to fully understand the motion of these micron-size organisms, which takes place at very low Reynolds number where friction dominates over inertia, we set out to measure their drag coefficients. As a starting point, we used a well-studied species of MTB with a corkscrew shape, Magnetospirillum magneticum AMB-1. Simulations were done to find the best external magnetic field strength at which to observe their diffusion. We then imaged non-motile cells placed in these preferred uniform magnetic fields and used automated image analysis to determine the position and orientation of the cells in each frame. This allowed calculating orientation correlation functions and mean-squared displacements, from which rotational and translational diffusion coefficients were obtained for each individual cell. We observed that the four principal drag coefficients of these cells greatly vary as a function of cell length as predicted for cylindrical or elliptical objects with comparable radius. However, we also detecting a coupling between the rotation around and translation along the long axis of the cell only observed for chiral objects. We were able for the first time to experimentally fully characterize the friction matrix for a micron-size elongated chiral object. Continuing our work on MTB, to study live cells for long periods of time, we looked to confine them in PDMS nanowells, but found that MTB were not growing well in this environment. We then turned to a device, which incorporated a PDMS microchannel to provide continuous nutrients and a gel membrane to enable cellular growth into a 2D monolayer. Hopefully, this experimental setup combined with time-lapse microscopy can in the future be used to observe cell growth and cell division, and further to determine whether the magnetosome of the mother is passed on equally between daughter cells. / Thesis / Master of Applied Science (MASc)

The purpose of this research is to numerically simulate, analyze, and visualize turbulent flow around rotating aerodynamic shaped 3-dimentional geometries using a custom-made software suite. The computational fluid dynamic program used for this research is called Numerical Wind Tunnel, NWT, which was developed by Dr. J. Militzer and his students over the last 15 years. In order to meet various simulation and prediction requirements of this research, the NWT was modified and improved by implementing many new features; in addition, many bugs have been fixed. Key features added to the NWT include improved boundary layer handling for Detached Eddy Simulation method, new implementations of Surrounding Cell Method and rewritten Lift and Drag Coefficients calculation algorithms, and new approaches to Mesh Refinement and Adaptation Criteria. The improved software is tested extensively by simulating turbulent flows around a rotating National Advisory Committee for Aeronautics (NACA) 0009 airfoil, and test results are compared with both experimental data and previous simulation data. The research was successful mainly because of the much-improved accuracy in predicting static lift and drag coefficients. Another achievement of this research is that the software also successfully predicted various events during an airfoil dynamic stall condition, which is a result of both accurate flow prediction and a NWT feature called Automatic Anisotropic Grid Adaptation.

Orientador: Rodolpho Vilhena de Moraes / Banca: Maria Cecília França de Paula Santos Zanardi / Banca: Valdemir Carrara / Resumo: Devido à sua dependência a um grande número de parâmetros de difícil determinação, o cálculo de coeficiente de arrasto para satélites artificiais torna-se extremamente complexo. Teorias, como as desenvolvidas por Schamberg e Sehnal levam em consideração o coeficiente de acomodação térmico e os ângulos de incidência e reflexão das moléculas na superfície do satélite. Outras teorias como a de Stalder e Zurick utilizam nas suas formulações os seguintes parâmetros: a razão entre as velocidades do satélite e das moléculas da atmosfera, o coeficiente de acomodação térmico, o ângulo de ataque e a razão entre as temperaturas da superfície do satélite e a temperatura das moléculas incidentes. Neste trabalho algumas teorias para o cálculo do coefienciente de arrasto são analisadas comparativamente. Exemplos são exibidos, utilizando como modelo os satélites SCD1, SCD2 e CBERS1. / Abstract: Drag coefficient computation for artificial satellite is extremely complex due to its dependence on several parameters that are difficult to determine. Some theories for drag coefficient computation, such as those developed by Schamberg and Sehnal, took into account the thermal accommodation coefficient and the incident and reflection angles of the molecules in the satellite surface. Others theories, such as the Stalder and Zurick theories, use in their formulations the following parameters: the ratio between the satellite velocity and the velocity of the molecules in the atmosphere, the thermal accommodation coefficient, the attack angle and the ratio between the temperatures of the satellite surface and of the incident molecules. In this work some theories for drag coefficients computation are comparatively analyzed. Examples are exhibited using the satellites SCD1, SCD2 and CBERS1 as models. / Mestre

Made available in DSpace on 2014-06-11T19:25:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2001Bitstream added on 2014-06-13T19:06:47Z : No. of bitstreams: 1 silva_tr_me_guara.pdf: 448943 bytes, checksum: 69cd9d252dfbcf9b51952987c7904c0b (MD5) / Devido à sua dependência a um grande número de parâmetros de difícil determinação, o cálculo de coeficiente de arrasto para satélites artificiais torna-se extremamente complexo. Teorias, como as desenvolvidas por Schamberg e Sehnal levam em consideração o coeficiente de acomodação térmico e os ângulos de incidência e reflexão das moléculas na superfície do satélite. Outras teorias como a de Stalder e Zurick utilizam nas suas formulações os seguintes parâmetros: a razão entre as velocidades do satélite e das moléculas da atmosfera, o coeficiente de acomodação térmico, o ângulo de ataque e a razão entre as temperaturas da superfície do satélite e a temperatura das moléculas incidentes. Neste trabalho algumas teorias para o cálculo do coefienciente de arrasto são analisadas comparativamente. Exemplos são exibidos, utilizando como modelo os satélites SCD1, SCD2 e CBERS1. / Drag coefficient computation for artificial satellite is extremely complex due to its dependence on several parameters that are difficult to determine. Some theories for drag coefficient computation, such as those developed by Schamberg and Sehnal, took into account the thermal accommodation coefficient and the incident and reflection angles of the molecules in the satellite surface. Others theories, such as the Stalder and Zurick theories, use in their formulations the following parameters: the ratio between the satellite velocity and the velocity of the molecules in the atmosphere, the thermal accommodation coefficient, the attack angle and the ratio between the temperatures of the satellite surface and of the incident molecules. In this work some theories for drag coefficients computation are comparatively analyzed. Examples are exhibited using the satellites SCD1, SCD2 and CBERS1 as models.

The accuracy of the calculated drag force in OpenRocket was examined in this investigation for a rocket traveling at subsonic, transonic and supersonic speeds. The idea was to compare the computed drag coefficients in OpenRocket to the drag coefficients obtained by running multiple computational fluid dynamics (CFD) simulations in Ansys Fluent. Specifically, the freestream Mach number and altitude parameters were varied for a geometric model of the Mjöllnir rocket. The results obtained converged several orders of magnitude and were exceptionally stable. Both the physical accuracy and numerical independence of the results was verified through examining the solutions' contour plots and conducting multiple sensitivity analyses. The conclusion was that OpenRocket overpredicts the Mjöllnir rocket's drag coefficients by 12 % to 73 % for all examined freestream Mach numbers and altitudes. Additionally, an empirical relationship was found for how the Mjöllnir rocket's drag coefficient changes with altitude and the freestream Mach number. In particular, it is a multivariate function that can be considered valid for an altitude of h ≤ 10 km and a freestream Mach number of 0.2 ≤ M ≤ 3.0. The empirical relationship fitted exceedingly well with simulation data and merits further investigation.

Estruturas treliçadas de linhas de transmissão submetidas à ação do vento têm sido utilizadas de forma rotineira em aplicações da engenharia estrutural há mais de um século. Entretanto, o conhecimento dos efeitos do vento sobre este tipo de estrutura é, ainda hoje, imperfeito e as prescrições das normas a respeito destes efeitos são, em muitos casos, mutuamente inconsistentes e em desacordo com os dados experimentais. Partindo deste contexto, no caso particular de estruturas para linhas de transmissão, podemos acrescentar que as normas existentes não são, em princípio, aplicáveis à maior parte das geometrias utilizadas nos projetos das torres. Além disso, maiores níveis de segurança e confiabilidade são atingidos quando a consideração criteriosa dos efeitos do vento é feita a partir da etapa de concepção sendo, geralmente, este o processo de menor custo e de maior eficiência. Sabe-se também que o modelo físico adotado para consideração dos carregamentos difere do real, seja pela forma de atuação ou pela complexidade para estimativa da interação entre fluido-estrutura. Nesse sentido, através do presente trabalho procurou-se: desenvolver e aperfeiçoar instrumentos e técnicas de medição de coeficientes de arrasto; verificar a aplicabilidade dos critérios de estimativa do carregamento devido ao vento sobre trechos de estruturas treliçadas; propor coeficientes de arrasto compatíveis com geometrias tradicionalmente utilizadas em torres de linhas de transmissão determinados a partir da aplicação de dois critérios de área de referência, a saber, área calculada e área projetada; além de comparar os resultados experimentais com outras referências como normas técnicas de projeto. Este trabalho de pesquisa contempla o estudo de duas torres de suspensão autoportantes em túnel de vento. Para a realização dos ensaios, através de modelos reduzidos, cada torre foi dividida em módulos. Os módulos foram ensaiados para diferentes ângulos de incidência do vento e também para diferentes níveis de velocidade do vento. As forças de arrasto sobre os modelos foram determinadas através de uma balança de forças unidirecional instalada na base da câmara de ensaios. / Transmission lines lattice structures submitted to wind action have been widely used in structural engineering applications for more than a century. However, the knowledge of the wind effect on this type of structure is yet imperfect, being the codes recommendations, in several cases, inconsistent and in disagreement with the experimental data. From this point of view, in the particular case of transmission lines structures, we can add that the existing codes are not, in principle, applicable to a large amount of geometries used in the towers design. Furthermore, largest safety and reliability levels are reached when careful consideration of the wind effects is made from the conception stage, being this process, in general, the less costly and the most efficient. It is also known that the physical model adopted for the consideration of the loads differs from the real, either for the way in which the load is really applied or the complexity for an accurate estimate of the fluid-structure interaction. In this sense, the present work had the aim of: developing and improving instrumentation and measurement techniques for drag coefficients; verifying the applicability of the criteria for estimating wind loads on modules of lattice structures; proposing drag coefficients applicable to geometries traditionally adopted in transmission lines towers, obtained from the application of the two reference areas criteria, calculated area and projected area; as well as comparing experimental results with other references such as design codes. The research contemplates wind tunnel studies of two self-supported suspension towers. For the accomplishment of the tests, through scaled models, each tower was divided in modules. The modules had been tested for different angles of incidence of the wind and also for different wind speeds. The drag forces on the models were measured through a unidirectional force balance installed in the base of the models.

Estruturas treliçadas de linhas de transmissão submetidas à ação do vento têm sido utilizadas de forma rotineira em aplicações da engenharia estrutural há mais de um século. Entretanto, o conhecimento dos efeitos do vento sobre este tipo de estrutura é, ainda hoje, imperfeito e as prescrições das normas a respeito destes efeitos são, em muitos casos, mutuamente inconsistentes e em desacordo com os dados experimentais. Partindo deste contexto, no caso particular de estruturas para linhas de transmissão, podemos acrescentar que as normas existentes não são, em princípio, aplicáveis à maior parte das geometrias utilizadas nos projetos das torres. Além disso, maiores níveis de segurança e confiabilidade são atingidos quando a consideração criteriosa dos efeitos do vento é feita a partir da etapa de concepção sendo, geralmente, este o processo de menor custo e de maior eficiência. Sabe-se também que o modelo físico adotado para consideração dos carregamentos difere do real, seja pela forma de atuação ou pela complexidade para estimativa da interação entre fluido-estrutura. Nesse sentido, através do presente trabalho procurou-se: desenvolver e aperfeiçoar instrumentos e técnicas de medição de coeficientes de arrasto; verificar a aplicabilidade dos critérios de estimativa do carregamento devido ao vento sobre trechos de estruturas treliçadas; propor coeficientes de arrasto compatíveis com geometrias tradicionalmente utilizadas em torres de linhas de transmissão determinados a partir da aplicação de dois critérios de área de referência, a saber, área calculada e área projetada; além de comparar os resultados experimentais com outras referências como normas técnicas de projeto. Este trabalho de pesquisa contempla o estudo de duas torres de suspensão autoportantes em túnel de vento. Para a realização dos ensaios, através de modelos reduzidos, cada torre foi dividida em módulos. Os módulos foram ensaiados para diferentes ângulos de incidência do vento e também para diferentes níveis de velocidade do vento. As forças de arrasto sobre os modelos foram determinadas através de uma balança de forças unidirecional instalada na base da câmara de ensaios. / Transmission lines lattice structures submitted to wind action have been widely used in structural engineering applications for more than a century. However, the knowledge of the wind effect on this type of structure is yet imperfect, being the codes recommendations, in several cases, inconsistent and in disagreement with the experimental data. From this point of view, in the particular case of transmission lines structures, we can add that the existing codes are not, in principle, applicable to a large amount of geometries used in the towers design. Furthermore, largest safety and reliability levels are reached when careful consideration of the wind effects is made from the conception stage, being this process, in general, the less costly and the most efficient. It is also known that the physical model adopted for the consideration of the loads differs from the real, either for the way in which the load is really applied or the complexity for an accurate estimate of the fluid-structure interaction. In this sense, the present work had the aim of: developing and improving instrumentation and measurement techniques for drag coefficients; verifying the applicability of the criteria for estimating wind loads on modules of lattice structures; proposing drag coefficients applicable to geometries traditionally adopted in transmission lines towers, obtained from the application of the two reference areas criteria, calculated area and projected area; as well as comparing experimental results with other references such as design codes. The research contemplates wind tunnel studies of two self-supported suspension towers. For the accomplishment of the tests, through scaled models, each tower was divided in modules. The modules had been tested for different angles of incidence of the wind and also for different wind speeds. The drag forces on the models were measured through a unidirectional force balance installed in the base of the models.

Estruturas treliçadas de linhas de transmissão submetidas à ação do vento têm sido utilizadas de forma rotineira em aplicações da engenharia estrutural há mais de um século. Entretanto, o conhecimento dos efeitos do vento sobre este tipo de estrutura é, ainda hoje, imperfeito e as prescrições das normas a respeito destes efeitos são, em muitos casos, mutuamente inconsistentes e em desacordo com os dados experimentais. Partindo deste contexto, no caso particular de estruturas para linhas de transmissão, podemos acrescentar que as normas existentes não são, em princípio, aplicáveis à maior parte das geometrias utilizadas nos projetos das torres. Além disso, maiores níveis de segurança e confiabilidade são atingidos quando a consideração criteriosa dos efeitos do vento é feita a partir da etapa de concepção sendo, geralmente, este o processo de menor custo e de maior eficiência. Sabe-se também que o modelo físico adotado para consideração dos carregamentos difere do real, seja pela forma de atuação ou pela complexidade para estimativa da interação entre fluido-estrutura. Nesse sentido, através do presente trabalho procurou-se: desenvolver e aperfeiçoar instrumentos e técnicas de medição de coeficientes de arrasto; verificar a aplicabilidade dos critérios de estimativa do carregamento devido ao vento sobre trechos de estruturas treliçadas; propor coeficientes de arrasto compatíveis com geometrias tradicionalmente utilizadas em torres de linhas de transmissão determinados a partir da aplicação de dois critérios de área de referência, a saber, área calculada e área projetada; além de comparar os resultados experimentais com outras referências como normas técnicas de projeto. Este trabalho de pesquisa contempla o estudo de duas torres de suspensão autoportantes em túnel de vento. Para a realização dos ensaios, através de modelos reduzidos, cada torre foi dividida em módulos. Os módulos foram ensaiados para diferentes ângulos de incidência do vento e também para diferentes níveis de velocidade do vento. As forças de arrasto sobre os modelos foram determinadas através de uma balança de forças unidirecional instalada na base da câmara de ensaios. / Transmission lines lattice structures submitted to wind action have been widely used in structural engineering applications for more than a century. However, the knowledge of the wind effect on this type of structure is yet imperfect, being the codes recommendations, in several cases, inconsistent and in disagreement with the experimental data. From this point of view, in the particular case of transmission lines structures, we can add that the existing codes are not, in principle, applicable to a large amount of geometries used in the towers design. Furthermore, largest safety and reliability levels are reached when careful consideration of the wind effects is made from the conception stage, being this process, in general, the less costly and the most efficient. It is also known that the physical model adopted for the consideration of the loads differs from the real, either for the way in which the load is really applied or the complexity for an accurate estimate of the fluid-structure interaction. In this sense, the present work had the aim of: developing and improving instrumentation and measurement techniques for drag coefficients; verifying the applicability of the criteria for estimating wind loads on modules of lattice structures; proposing drag coefficients applicable to geometries traditionally adopted in transmission lines towers, obtained from the application of the two reference areas criteria, calculated area and projected area; as well as comparing experimental results with other references such as design codes. The research contemplates wind tunnel studies of two self-supported suspension towers. For the accomplishment of the tests, through scaled models, each tower was divided in modules. The modules had been tested for different angles of incidence of the wind and also for different wind speeds. The drag forces on the models were measured through a unidirectional force balance installed in the base of the models.

<div> <div> <div> <p>Commercial vehicles in the United States account for a significant fraction of greenhouse gas emissions and NOx emissions. The objectives of this work are reduction in commercial vehicle NOx emissions through enhanced aftertreatment thermal management via diesel engine variable valve actuation and the reduction of commercial vehicle fuel consumption/GHG emissions by enabling more effective class 8 truck platooning. </p> <p><br></p><p>First, a novel diesel engine aftertreatment thermal management strategy is proposed which utilizes a 2-stroke breathing variable value actuation strategy to increase the mass flow rate of exhaust gas. Experiments showed that when allowed to operate with modestly higher engine-out emissions, temperatures comparable to baseline could be achieved with a 1.75x exhaust mass flow rate, which could be beneficial for heating the SCR catalyst in a cold-start scenario. </p> <p><br></p><p>Second, a methodology is presented for characterizing aerodynamic drag coefficients of platooning trucks using experimental track-test data, which allowed for the development of high-fidelity platoon simulations and thereby enabled rapid development of advanced platoon controllers. Single truck and platoon drag coefficients were calculated for late model year Peterbilt 579’s based on experimental data collected during J1321 fuel economy tests for a two-truck platoon at 65 mph with a 55’ truck gap. Results show drag coefficients of 0.53, 0.50, and 0.45 for a single truck, a platoon front truck, and a platoon rear truck, respectively. </p> <p><br></p><p>Finally, a PID-based platoon controller is presented for maximizing fuel savings and gap control on hilly terrain using a dynamically-variable platoon gap. The controller was vetted in simulation and demonstrated on a vehicle in closed-course functionality testing. Simulations show that the controller is capable of 6-9% rear truck fuel savings on a heavily-graded route compared to a production-intent platoon controller, while increasing control over the truck gap to discourage other vehicles from cutting in. </p></div></div></div>