The purpose of this thesis work was to design a new shape for the BYU Supermileage vehicle in order to improve its fuel efficiency. Computational Fluid Dynamics (CFD) was used to obtain the coefficient of drag (CD) and drag area of the current baseline vehicle at a Reynolds number of 1.6x10^6 and 8.7x10^5. Then a new shape was developed using mesh morphing software. The new shape was imported into the CFD program and the drag figures and airflow plots from the modified design were compared with the baseline vehicle. Scale models of the vehicles were also printed using a 3D printer in order to perform wind tunnel testing. The models were installed in the wind tunnel and the coefficient of drag and drag area were compared at a Reynolds number around 8.7x10^5.It was found from the CFD results that the new vehicle shape (labelled Model C) caused a 10.8% reduction in CD and a 17.4% reduction in drag area under fully laminar flow. Smaller drag reductions were observed when the flow was fully turbulent. From the wind tunnel comparisons, it was found that Model C reduced CD by 5.3% and drag area by 11.4%, while the fully laminar CFD results at Re = 8.7x10^5 showed that Model C reduced CD by 9.8% and drag area by 15.9%. Smaller drag reductions were again observed for fully turbulent flow. Thus in order to improve the aerodynamic performance, the current vehicle shape should be changed to match that of Model C, and laminar flow should be encouraged over as much of the wetted area as possible.

One approach recently proposed for reducing the frictional resistance to liquid flow in microchannels is the patterning of micro-ribs and cavities on the channel walls. When treated with a hydrophobic coating, the liquid flowing in the microchannel wets only the top surfaces of the ribs, and does not penetrate into the cavities, provided the pressure is not too high. The net result is a reduction in the surface contact area between channel walls and the flowing liquid. For micro-ribs and cavities that are aligned normal to the channel axis (principal flow direction), these micropatterns form a repeating, periodic structure. This thesis presents numerical results of a study exploring the momentum and thermal transport in a parallel plate microchannel with such microengineered walls. The liquid-vapor interface (meniscus) in the cavity regions is approximated as flat in the numerical analysis. Two conditions are explored with regard to the cavity region: 1) The liquid flow at the liquid-vapor interface is treated as shear-free (vanishing viscosity in the vapor region), and 2) the liquid flow in the microchannel core and the vapor flow within the cavity are coupled through the velocity and shear stress matching at the interface. Predictions reveal that significant reductions in the frictional pressure drop (as large as 80%) can be achieved relative to the classical smooth channel Stokes flow. In general, reductions in the friction factor-Reynolds number product (fRe) are greater as the cavity-to-rib length ratio is increased (increasing shear-free fraction), as the relative module length (length of a rib-cavity module over the channel hydraulic diameter) is increased, as the Reynolds number decreases, and as the vapor cavity depth increases. The thermal transport results predict lower average Nusselt (Nu) numbers as the cavity-to-rib length ratio is increased (increasing shear-free fraction), as the relative module length (is increased, and as the Reynolds number decreases with little dependence on cavity depth. The ratio of Nu to fRe was evaluated to characterize the relative change in heat transfer with respect to the reduction in driving pressure. Results show that the benefits of reduction in driving pressure outweigh the cost of reduction in heat transfer at higher Reynolds numbers and narrower relative channel widths.

Flight testing methods are developed to find the drag polar for small UAVs powered by electric motors with fixed-pitch propellers. Wind tunnel testing was used to characterize the propeller-motor efficiency. The drag polar was constructed using data from flight tests. The proposed methods were implemented for a small UAV. A drag polar was found for this aircraft with CDo equal to 0.021, K1 equal to 0.229, and K2 equal to -0.056. This drag polar was then used to find the following performance parameters; maximum velocity, minimum velocity, velocity for maximum range, velocity for maximum endurance, maximum rate of climb, maximum climb angle, minimum turn radius, maximum turn rate, and maximum bank angle. Applications in UAV control and mission planning are also proposed.

Numerous practical applications exist where dispersed solid particles are transported within a turbulent accelerating or decelerating gaseous flow. The large density variation between phases creates the potential for significant differences in velocity known as velocity slip. Flow over a backward facing step provides a well characterized, turbulent, decelerating flow useful for measuring the relative velocities of the solid and gaseous phases in order to determine velocity slip and particle drag. Numerous investigations have been conducted to determine the gas phase velocity in a backward facing step for both laminar and turbulent flows and therefore the gas phase flow is well know and documented. Furthermore, some studies have also been conducted to determine the velocity of various sizes of spherical particles in a backward facing step and compared with their corresponding gas phase velocities. Few if any velocity measurements have been made for non-spherical particles in a backward facing step. In this work, a Phase Doppler Particle Analyzer (PDA) was used to measure gas and particle phase velocities in a backward facing step. The step produced a 2:1 increase in cross sectional area with a Reynolds number of 22,000 (based on step height) upstream of the step. Spherical particles of 1 – 10 μm with an average diameter of 4μm were used to measure the gas phase velocity. At least three sizes in the range of (38 – 212 μm) for four different particles shapes were studied. The shapes included: spheres, flakes, gravel, and cylinders. Since the PDPA is not able to measure the size of the non-spherical particles, the particles were first separated into size bins and a technique was developed using the PMT (photo multiplier tubes) gain to isolate the particle size of interest for each size measured. The same technique was also used to measure terminal velocities of the particles in quiescent air. The measured gas phase velocity and spherical solid phase particles were in good agreement with previous measurements in the literature. The results showed relative velocities between the particles and gas phase to be in the range of 0 – 3 m/s which is in transition between stokes flow and fully developed turbulent flow. Drag coefficients were an order magnitude higher for non-spherical particles in turbulent flows in comparison to stokes flow which agreed reasonably well with quiescent terminal velocity drag. This information is valuable for modeling turbulent two-phase flows since most assumptions of the drag are currently based on correlations from empirical data with particles moving through a still fluid.

Due to the increase of application in a number of emerging technologies, a growing amount of research has focused on the reduction of drag in microfluidic transport. A novel approach reported in the recent literature is to fabricate micro-ribs and cavities in the channel wall that are then treated with a hydrophobic coating. Such surfaces have been termed super- or ultrahydrophobic and the contact area between the flowing liquid and the solid wall is greatly reduced. Further, due to the scale of the micropatterned structures, the liquid is unable to wet the cavity and a liquid meniscus is formed between ribs. This creates a liquid-vapor interface at the cavity regions and renders surfaces with alternating regions of no-slip and of reduced shear on the microscale. This thesis reports the numerical study of hydrodynamically fully-developed laminar and turbulent flows through a parallel plate channel with walls exhibiting micro-ribs and cavities oriented parallel to the flow direction, where fully developed turbulent flow is considered in a time-averaged sense. Three laminar flow models are implemented to investigate the liquid-vapor interface and to account for the effects of the vapor motion in the cavity regions. For each of the laminar flow models, the liquid-vapor interface was idealized as a flat interface. As a benchmark for the proceeding laminar flow models, the first model considers the case of a vanishing shear stress at the interface between the liquid and vapor domains. Effects of the vapor motion in the cavity are then accounted for in a one-dimensional cavity model where the vapor velocity is considered to be dependent on the wall normal coordinate only, followed by a two-dimensional cavity model that accounts for the vapor velocity's dependence on the transverse coordinate as well. The vapor cavity is modeled analytically and is coupled to the liquid domain by equating the fluid velocities and shear stresses at the liquid-vapor interface. In the turbulent flow model the liquid-vapor interface is idealized as a flat interface with a zero shear stress boundary condition. In general the numerical predictions show a reduction in the total frictional resistance as the cavity width is increased relative to the channel width, the channel height-to-width aspect ratio is decreased, and the vapor cavity depth is increased. The frictional resistance is also reduced with increased Reynolds number in the turbulent flow case. In the range of parameters examined for each fluid flow regime, reductions in drag as high as 91% and 90% are reported for the laminar flow and turbulent flow models, respectively. Under similar conditions however, the turbulent flow results indicate a greater reduction in flow resistance than for the laminar flow scenario. Based on an analysis of the obtained data, analytical expressions are proposed for both laminar and turbulent flow which facilitates the prediction of the frictional resistance.

There is significant interest in reducing the frictional resistance that occurs along a surface in contact with a liquid. A novel approach to reducing the frictional resistance across a liquid-solid interface is the use of superhydrophobic surfaces. superhydrophobic surfaces are created in this work by the use of micro-fabrication techniques where systematic roughness is fabricated on a substrate surface which is subsequently treated with a hydrophobic coating. This work reports an experimental study of superhydrophobic surfaces used to reduce drag in both laminar and turbulent channel flows. In the laminar flow regime reductions in frictional resistance greater than 55% were measured in microchannels consisting of superhydrophobic walls. The reduction in frictional resistance for laminar flow in microchannels with superhydrophobic walls was shown to be dependent on the rib/cavity orientation, with greater reduction achieved when the ribs/cavities were aligned parallel with the direction of the flow. Also, the ratio of the cavity width to the combined rib/cavity pitch and the ratio of the combined rib/cavity pitch to the microchannel hydraulic diameter exercise influence on the frictional resistance. The condition when the flowing liquid was allowed to completely "wet" the cavities was also explored. Generalized expressions enabling prediction of the classical friction factor-Reynolds number product as a function of the relevant governing parameters were also developed. The influence of superhydrophobic surfaces in turbulent flow was explored in macrochannels using particle imaging velocimetry (PIV). For the turbulent flow regime the time-averaged velocity profiles revealed no discernible slip velocity at the superhydrophobic wall. However, the results did show that the superhydrophobic surfaces exhibits an influence on the streamwise and wall-normal turbulence intensities, the turbulent shear stress, the total shear stress distributions, and the turbulence production in the channel. From the total shear stress distributions in the channel the coefficient of friction at the channel walls was determined. The results showed that for the superhydrophobic surface with ribs and cavities oriented parallel to the flow direction a reduction in the coefficient of friction as high as 16% was achieved compared to a smooth wall channel. Superhydrophobic surfaces with ribs and cavities oriented transverse to the flow direction showed a modest increase in the coefficient of friction. Differential pressure measurements in the turbulent flow channel were also acquired and used to calculate the channel average friction factor.

Energy efficiency and propulsive characteristics of a 10 cm undulatory rainbow trout (oncorhynchus mykiss) swimming in a stationary position are considered. Two CFD simulations are performed utilizing dynamic grid meshing (FLUENT 6.3). The first simulation uses a laminar flow model with an added hydrofoil shape in order to test if thrust and drag can be brought to unity. The second simulation uses a Large-Eddy Simulation (LES) turbulence model to determine if transition to turbulence along the fish's surface leads to boundary layer separation. The expected results caused by adding these two features to earlier simulations do not occur. Thrust and drag are not found to be equal with usage of the thicker fish shape; instead both thrust and drag increase by 40-80% while diverging in value. Evidence of boundary layer separation is not present with usage of the LES turbulence model. Swimming energy efficiency is calculated to be 70% in both simulations. A brief analyses of boundary layer and downstream wake are included, showing general agreement with earlier studies. Limitations of the simulation are discussed. Future work regarding the author's preparation for an additional simulation of a rainbow trout utilizing a swimming method known as the Karman Gait is also considered. This preparation includes the creation of a 2-D grid domain and programs to define the kinematics of the fish and produce a specified vortex inlet condition.

I följande studie har syftet varit att undersöka tre forskares uppfattningar och definitioner kring begreppet psykopati. I denna kvalitativa studie användes semistrukturerade intervjuer som datainsamlingsmetod. Genom den tematiska analysen har därefter två teman identifierats. Dessa var centrala drag samt arv och miljö̈. Urvalet bestod av totalt tre forskare verksamma inom bland annat ämnesområdet psykopati. Tidigare forskning som undersökt begreppet menar att det på grund av begreppets komplexitet är svårt att definiera. Den insamlade empirin tolkades därefter utifrån den biopsykosociala modellen. Modellen menar att biologiska, psykologiska samt sociologiska faktorer tillsammans kan syfta till att förklara definitionen och uppfattningen av begreppet psykopati. Studiens resultat visar att studiens deltagare till stor del definierar och uppfattar begreppet likadant. Uppfattningarna baseras dock till stor del på att studiens deltagare har en gedigen kunskap inom psykopati. De slutsatser som dras av denna studie är att det på grund av begreppets olika dimensioner samt komplexitet kan behövas en tydligare definition.

Vi har genomfört en praxisnära forskning där syftet var att kartlägga vilka aspekter som är kritiska för att kunna positionera sig med hjälp av en karta. Syftet var också att identifiera vilka olika kunskapsnivåer som finns i en klass i årskurs 7. Studiens metod utgår ifrån delar av learning study som har variationsteorin som grund kombinerat med delar av fenomenografin som forskningsansats. Studien genomfördes på en grundskola i Skåne i en klass i årskurs 7 med 26 elever. För att undersöka vilka kritiska aspekter som finns i klassen har vi genomfört fokusgruppintervjuer, test i form av linjeorientering, skriftliga reflektioner av linjeorienteringen samt observationer. Den insamlade empirin har analyserats och diskuterats utifrån variationsteorin. De kritiska aspekter vi hittade var strategi för positionering, förhållandet mellan karta och verklighet, rumsuppfattning, passa kartan, tumgreppet, kartans tecken och färger, förmåga att avläsa höjdskillnader, förmåga att förstå avstånd/skala samt förmåga att använda referenspunkter. Fyra kategorier som kvalitativt skiljer sig åt har identifierats och beskrivits. Kategori 1 saknar kunskap i samtliga funna kritiska aspekter. Kategori 2 har en grundläggande strategi för hur de skall positionera sig med hjälp av kartan. Eleverna kan passa kartan till viss del och har en grundläggande förmåga att använda kartans tecken samt avläsa dess skala. Det är först i kategori 3 eleverna får syn på den kritiska aspekten kartans färger. Eleverna i kategori 3 har relativt god förmåga att passa kartan och kan i större utsträckning än kategori 2 använda sig av kartans tecken. Eleverna i kategori 3 har en utvecklad förståelse för samband mellan karta och verklighet. Det som skiljer kategori 3 från 4 är att eleverna i kategori 4 har en djupare förmåga i samtliga kritiska aspekter utom förmågan att avläsa avstånd/skala där inga nämnvärda skillnader finns mellan kategorierna. En slutsats var att det fanns en stor spridning i vad som var kritiskt i förmågan att kunna positionera sig med hjälp av en karta. Det går inte att dra några större slutsatser av vår kategorisering eftersom vårt syfte var att kartlägga och inte utveckla elevernas förmåga i varje kategori. Genom att utgå från resultatet i vår studie, de kritiska aspekterna och hur de skiljer sig i de olika nivåerna, kan ett undervisningsupplägg, nästa steg i en learning study, utformas med hjälp av variationsteorin. / We have implemented a practice-based research. The aim was to identify the aspects that are critical in order to position themselves with the help of a map. The aim was also to identify the different levels of knowledge that exists in a class in 7th grade. The study's methodology is based on variation theory and elements of a learning study combined with elements of phenomenography as a research approach. The study was conducted at an elementary school in southern Sweden in a class in 7th grade with 26 students. To investigate the critical aspects in the class, we have conducted focus group interviews, a test in the form of a line orienteering, written reflections of the line orientation and observations. The collected empirical data has been analyzed and discussed on the basis of variation theory. The critical aspects we found was strategy for positioning, the relationship between the map and reality, spatial awareness, fitting the map with reality, the thumb grip, map symbols and map colors, ability to read the elevation changes, the ability to understand the range / scale and the ability to use reference points. Four categories was identified and described. The first category lack knowledge in all the found critical aspects. Category 2 has a basic strategy for how to position themselves with the help of a map. Students have a basic ability to fit the map with reality and have a basic ability to use the map's symbols and read the scale. It is first in Category 3 students find out the critical aspect of the map colors. Students in Category 3 have relatively good ability to fit the map with reality and they are better than category 2 to use the map's symbols. Students in Category 3 has an improved understanding of the relationship between the map and reality. What distinguishes Category 3 from 4 is that students in Category 4 has a deeper ability in all critical aspects except the ability to read the distance / range where no significant differences were found between the categories. One conclusion was that there were a large spread in what was critical in the ability to position themselves with the help of a map. It is not possible to draw any major conclusions from our categorization because the purpose was to identify and not develop students' ability in each category. The critical aspects we found and how they vary in the different levels can be used to create a teaching approach, the next step in a learning study, using variation theory.

Energy needs are projected to continue to increase in the coming decades, and with the drive to use more clean energy to combat climate change, nuclear energy is poised to become an important player in the energy portfolio of the world. Due to the unique nature of nuclear energy, it is always vital to have safe and efficient generation of that energy. In current light water reactors, the most common fuel is uranium dioxide (UO2), an oxide ceramic. There is also ongoing research examining uranium-based based metallic fuels, such as uranium-molybdenum (U-Mo) fuels with low uranium (U) enrichment for research reactors as part of a broader effort to combat nuclear proliferation, and uranium-zirconium-based fuels for Generation IV fast reactors. Each nuclear fuel has weaknesses that need to be addressed for safer and more efficient use. Two major challenges of using UO¬2 are the fission gas (e.g. xenon) release and the decreasing thermal conductivity with increasing burnup. In UMo alloys, the major weakness is the breakaway swelling that occurs at high fission densities. The challenges presented by both fuel types are heavily impacted by microstructure, and several studies have identified that the initial microstructure of the fuel in particular (e.g. initial grain size and grain aspect ratio) plays a large role in determining when and how quickly these processes occur. Thus, knowledge of how such initial microstructures evolve is paramount in having stable and predictable fission gas release and thermal conductivity decrease (in UO2) and fuel swelling (in UMo alloys). Mobility is a critical grain boundary (GB) property that impacts microstructural evolution. Existing literature examines GB mobility for a few specific boundaries but does not (in general) identify the anisotropy relationships that this property has. This work first examined the anisotropy in GB mobility, specifically identifying the anisotropy trend for the low-index rotation axes for tilt GBs in BCC γ U, and fluorite UO2 via molecular dynamics simulation. GB mobility is calculated using the shrinking cylindrical grain method, which uses the capillary effect induced by the GB curvature to drive grain growth. The mobilities are calculated for different rotation axes, misorientation angles, and temperatures in these systems. The results indicated that the density of the atomic plane perpendicular to the (tilt) GB plane (which is also perpendicular to the rotation axis) significantly impacts which GB rotation axis has the fastest boundaries. Specifically, the atomic plane that has a higher density tends to have a faster mobility, because it is more efficient for atoms moving across the GB along such planes. For example, for body-centered cubic materials, the <110> tilt GBs are determined to have the fastest mobilities, while face-centered cubic (FCC) and FCC-like structures such as fluorite have <111> tilt GBs as the fastest. Knowledge of GB mobility and its anisotropy in pure materials is helpful as a baseline, but real materials have solutes or impurities (both intentionally and unintentionally) which are known to affect GB mobility by processes such as solute drag and Zener pinning. Additionally, in reactors, nuclear fission can produce many fission products, each of which acts as an additional impurity that will interact with the GB in some way. Because the initial microstructure and its subsequent evolution are vital for addressing the challenges of using nuclear fuel as described above, knowledge of the impacts of these impurities on GB mobility is required. Therefore, this work examined the impact of solutes and impurities on GB mobility and its anisotropy. In particular, the solute effect was examined using the UMo alloy system, while the impurity effect was examined using Xe (a very common fission product) in the γ U, UMo, and UO2 systems. It is found that both Mo and Xe can cause a solute drag effect on GB mobility in the γ U system, with the effect of Xe being stronger than Mo at the same solute/impurity concentration. Xe also causes a solute drag effect in UO2, though the magnitude of the effect is interatomic-potential-dependent. The mobility anisotropy trend was found to disappear at high solute and impurity concentrations in the metallic U and UMo systems but was largely unaffected in the UO2 system. These results not only increase our fundamental understanding of GB mobility, its anisotropy, and solute/impurity drag effects, but also can be used as inputs for mesoscale simulations to examine polycrystalline grain growth with anisotropic GB mobility and in turn examine how the fuel performance parameters change with these properties. / Doctor of Philosophy / Worldwide, energy needs continue to increase each year. Concerns related to climate change have led to an increased emphasis on renewable energies such as solar and wind, but the limitations of these resources prevent them from being the only energy sources. Nuclear energy is uniquely positioned to address several energy concerns: it is clean (no carbon emissions and air pollution), reliable (for example, 24/7 energy production, independent of weather), and energy-dense (one kilogram of fissile uranium provides roughly the same amount of energy as 3000 metric tons of coal). Currently, nuclear energy provides roughly 20% of the energy of the United States, but future predictions show a decrease in the total share of energy generation due to aging systems and a limited number of new reactors being built. The safety and efficacy of existing and future reactors are among the primary concerns for being able to allow nuclear energy to increase its energy share. To determine the safety and efficacy of new reactor designs, a computer simulation tool called fuel performance modeling has been used over the last few decades. This tool requires several material properties as input, one of which is how the nuclear reactor fuel microstructure changes based on a variety of conditions. A significant process contributing to microstructural change is grain growth. Grains (crystallites that make up the whole material) meet at interfaces called grain boundaries (GBs), and these GBs have two properties that largely determine how grain growth occurs: energy and mobility. Significant effort is being put into understanding these properties and their anisotropy, or how they change based on the GB character which is the relative mismatch between the two grains. This work contributes additional understanding of GB mobility anisotropy in two nuclear fuels: uranium dioxide (UO2, the primary fuel in current reactors) and a uranium-molybdenum (UMo) alloy (the primary fuel for newer research reactors). In particular, computer simulation is used to determine GB mobility for several unique GB systems. It is found that for pure nuclear fuels, GB mobility anisotropy is largely determined by which atomic plane has the highest density perpendicular to the GB. When the fuel is no longer pure (through the addition of alloying elements or other impurities) the anisotropy changes significantly in UMo fuels, such that at high concentrations of solute or impurities there is little to no anisotropy, while very little change is observed in the anisotropy in UO2.