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The military's desire for ducted fan vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) stems from the vehicles' relatively small size, safety in tight quarters, increased payload capacity for their size, and their ability to hover for surveillance missions. However, undesirable aerodynamic characteristics are associated with these vehicles in crosswinds, namely momentum drag and asymmetric duct lift. Because the duct itself, and not the fan, is the root cause of these unfavorable aerodynamic attributes, various lip shapes were tested to determine the effects of leading edge radius of curvature and duct wall thickness. It was found that a lip with a small leading edge radius performed best in forward flight and crosswind conditions, while the performance of a lip with a large leading edge radius was enhanced in static conditions. Through tuft flow visualization and static pressure measurements it was determined that the reason for the difference in performance between the two lips was due to flow separation on the interior of the duct lip surface. Control vanes positioned aft of the duct were tested as the primary attitude control for the vehicle. An empirical control vane model was created based on the static data for the control vanes, and it was applied to wind tunnel test results to determine the required control vane angle for trim. Wind tunnel testing showed the control vanes were capable of trimming out the adverse pitching moment generated by the duct, but at some flight speeds large vane deflections were necessary. Additional control devices placed at the lip of the duct and stabilizer vanes positioned aft of the duct were tested to reduce the amount of control vane deflection required for trim. It was found that the duct deflector control effector had the largest impact on the adverse pitching moment, while the stabilizer vanes were only effective at low crosswind velocities. / Master of Science

The analysis of the turbulent flows in nuclear fuel bundles is a very interesting task to optimize the efficiency of modern nuclear power plants. The proposed study utilizes Computational Fluid Dynamics (CFD) to characterize the flow pattern generated in a fuel bundle with Spacer Grids (SG) and Mixing Vanes (MV). CFD calculations were performed using different turbulence models for steady state simulations. Large Eddy Simulations (LES) scheme was applied to time dependent cases. The simulations were compared with the experimental data measured at Texas A&M University fuel bundle experimental facility. Also, another objective is to develop some new coarse mesh approaches for modeling MV to include these structures in the prospective of quarter of core simulations; MV and SG are usually modeled with porous media, since the computational power required to solve the full geometry is still unacceptable. The new contribution of the study is the definition and implementation of a Momentum Sources Forcing approach that allows a detailed definition of MV and SG for coarse mesh calculations. The proposed method was investigated using different turbulence models and different numerical schemes. Also, LES calculations allowed the study of Fluid Structure Interaction (FSI), that generates vibration problems and failure of nuclear fuel pins. A spectral analysis of the forces acting on the fuel pins walls was developed. In conclusion, a comprehensive study of fuel bundle problem was proposed with benchmark of the computational techniques to the experimental data.

Until the beginning of the 1900:th century the paper making process was handicraft. The paper machines that have been developed since then are as impressing in size as fascinating when it comes to the technique. The process has always been improved to give a better paper for lower costs, with as short manufacture time as possible. Stratified forming has been a reality since 1830. From the beginning it was applied to board and paperboard. Now it is also the most common method for making tissue and one paper mill in Austria use it for fine paper. Stratified forming can be categorized as separate forming or simultaneous forming. Separate forming means using several headboxes and sometimes even several wires. Simultaneous forming means using only one stratified headbox. This method has many advantages over separate forming, inter alia improved economy, quality, wood exchange and higher runability of the paper machine. Several experiments have been done with simultaneous forming of different fibres by placing a fibre with high bulk in the middle layer and a smooth fibre on the surface layers. The results has shown that by using this method both the bending stiffness and surface properties are improved, or a lower grammage paper is obtained with maintaining quality. Simultaneous forming can also be used to stratify fillers in layers where they are most efficient. In that way both paper quality and economy is improved. Simultaneous forming is also used for fractionated pulp. Fractionation means separating springwood fibre from summerwood fibre, and placing them in separate layers. Research results of fractionated pulp show about the same result as simultaneous forming of different fibres.

The Diploma Thesis is focused to create the mathematical model of operating kinematic model for turbocharger DAVNT (Double Axle Variable Nozzle Turbine) for setting the position of vanes. The work contains a brief overview of supercharge and types of turbochargers. The main part contains a mathematical model which examines the behavior of the mechanism with considering of wear among the parts. It also includes assessment of changing in various parts of the nodes caused by mechanism wear and their influence on the mechanism due to important parameters which characterizes the mechanism. The evaluation is completed by optimizing the parameters. The final section contains the static calculation of internal forces and assessment of actuator position relative to mechanism load.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / This paper, evaluates a proposal for an external bend fluvial erosion control, using submerged vanes as velocity and shear stress control, verifying its effectiveness by modeling in Iber to calculate the scour produced by discharges with different return periods. The results indicate that the velocity, shear stress and scour decrease along the curve, due to submerged vanes.

The Utah Department of Transportation commissioned a study to determine whether or not shallow-flow rock structures could reliably be used at bridge abutments in place of riprap. Research was conducted in a two-phase effort beginning with numerical modeling and ending with field verification of model findings. As part of phase one, two finite element meshes were created in Surface-water Modeling Software (SMS) and analyzed with FESWMS-2DH. Second, field studies were conducted and a preliminary database was developed to track field studies conducted on 98 shallow-flow rock structures in Utah. Data organization in ArcGIS® and Microsoft Access® is presented followed by instructions on how to use the database. Both numerical model and field research results indicate that shallow-flow rock structures are not viable scour countermeasures at bridges.

Using Computational Fluid Dynamics Simulations, the flow in the new University of Sydney closed circuit wind tunnel has been analyzed prior to the construction of the tunnel. The objective was to obtain a uniform flow in the test section of the wind tunnel while keeping the pressure losses over the tunnel as low as possible. This was achieved by using several flow-improving components such as guide vanes, screens, a honeycomb and a settling chamber. The guide vanes were used in the corners and in the diverging part leading into the settling chamber, giving a significant improvement of the flow as they prevent it from taking undesired paths. The settling chamber is used to decelerate the flow before it is accelerated when leaving the settling chamber, a process which reduces the turbulence in the flow. Screens were used in the settling chamber to further improve the flow by imposing a pressure drop which evens out differences in the flow speed and reduces the turbulence. The honeycomb, which is situated in the end of the settling chamber, makes the flow more uniform by forcing it to go in only one direction. A uniform flow was obtained using three screens and one honeycomb together with the guide vanes and the settling chamber.

Experiments investigating complex flows in rod bundles with spacer grids that have mixing devices (such as flow mixing vanes) have mostly been performed using single-point measurements. Although these measurements allow local comparisons of experimental and numerical data they provide little insight because the discrepancies can be due to the integrated effects of many complex flow phenomena such as wake-wake, wake-vane, and vane-boundary layer interactions occurring simultaneously in a complex flow environment. In order to validate the simulations results, detailed comparison with experimental data must be done. This work describes an experimental database obtained using Time Resolved Particle Image Velocimetry (TR-PIV) measurements within a 5 x 5 rod bundle with spacer-grids. Measurements were performed using two different grid designs. One typical of Boiling Water Reactors (BWR) with swirl type mixing vanes and the other typical of Pressurized Water Reactors (PWR) with split type mixing vanes. High quality data was obtained in the vicinity of the grid using the multi-scale approach. One of the unique characteristic of this set-up is the use of the Matched Index of Refraction (MIR) technique employed in this investigation. This approach allows the use of high temporal and spatial non-intrusive dynamic measurement techniques to investigate the flow evolution below and immediately above the spacer. The experimental data presented includes explanation of the various cases tested such as test rig dimensions, measurement zones, the test equipment and the boundary conditions in order to provide appropriate data for comparison with Computational Fluid Dynamics (CFD) simulations. Turbulence parameters of the obtained data are analyzed in order to gain insight of the physical phenomena. The shape of the velocity profile at various distances from the spacer show important modifications passing the grid which delineates the significant effects of the presence of the grid spacer. Influence of the vanes wake in the global velocity was quantified to be up to a distance of 4 hydraulic diameters from the edge of the grid.Spatial and temporal correlations in the two measured dimensions were performed to quantify the time and length scales present in the flow in the vicinity of the grids and its influence in the flow modification induced by the vanes. Detection of vortex cores was performed using the vorticity, swirl strength and Galilean decomposition approach. The resulted cores were then tracked in time, in order to observe the evolution of the structures under the influence of the vanes for each grid. Vortex stretching was quantified in order to gain insight of the energy dissipation process normally associated with the phenomena. This work presents data in a single-phase flow situation and an analysis of these data for understanding complex flow structure. This data provide for the first time detailed temporal velocity full field which can be used to validate CFD codes.

This dissertation recasts the history of nudity in art as a history of ecology. Art historians have long emphasized that depictions of the nude body make visible social relationships structured by gender, race, and class. I contend that ecological relationships—among human beings, fellow living things, and their environments—lie latent in these same artworks. My argument unfolds in the context of the nineteenth-century United States, a place of profound and lasting change that transformed how the human body was understood and represented. Taking seriously the historical euphemism “the garb of nature,” I look anew at nudity across artistic media. Three chronological chapters expand outward in scale and engage with different aspects of the natural world: I examine an ivory miniature of a white woman’s bare breasts, a wet-collodion negative of unclothed Civil War soldiers bathing outdoors, and an enormous sculptural weathervane on the New York City skyline. In each case, I grapple with the contexts in which these artworks emerged, encompassing enslavement, war, colonialism, hunting, pollution, and industrialization—all practices premised upon social and ecological hierarchy. Yet my analysis reveals that these artworks attest not to hierarchy but to the vital interdependence of people and the natural world. Together, these case studies chart a new approach to nudity in art, attuned to both the social and ecological stakes of representation.