The VT i-Ship Lab has been assigned the task of designing and building a Personal Hydrofoil Craft capable of carrying two people, featuring the distinctive capabilities of foiling and diving. This thesis examines the attributes of fully submerged hydrofoils and their prospective advancements. Diverse configurations of fully submerged hydrofoils are scrutinized, accompanied by an exploration of their respective stability characteristics. A comprehensive analysis is conducted on the design space trade-offs, incorporating potential flow-based methodologies such as the lifting line and vortex lattice methods, encompassing considerations for the free surface, structural computations, and propulsion optimization. In conjunction with the design study computational fluid dynamics is employed to verify the estimated values and to fine-tune the system allowing for a robust low-fidelity system that can quickly estimate the appropriate hydrofoil arrangement for the desired conditions. Various hydrofoil and craft configurations are explored discussing the trade-offs with a final design being chosen and a thorough mechanical design pursued. / Master of Science / The VT i-Ship Lab is conducting research on a watercraft known as a "Personal Hydrofoil Craft." This vehicle is designed to carry two people, glide on the water's surface, and dive underwater. Hydrofoil crafts use specialized underwater wings to reduce resistance and enhance efficiency. Our focus is on fully submerged hydrofoils, studying their stability and efficiency. We employ computer simulations and advanced methods to design and optimize these submerged hydrofoils. The goal is to enhance our understanding of their functionality and performance through real-life experiments. This research has the potential to improve watercraft technology, leading to more efficient and stable boats in the future. By exploring the science behind hydrofoil designs, we aim to contribute valuable insights to the field of water transportation.

A swirl injector for a rocket engine being developed by \emph{AESIR} (Association of EngineeringStudents in Rocketry) was simulated with different geometric parameters. The swirl injector is usedto atomize the ethanol used as fuel and to create a spray that mixes well with the oxidizer withinthe combustion chamber. Inlet slot angle (90, 75, 60 and 45 degrees), swirl chamber length (15, 20and 25 mm) and outlet orifice diameter (3, 6 and 9 mm) were examined.Previous studies in swirl injectors show that CFD can be used to analyze the flow in such aninjector, furthermore theoretical models exist that can predict some of the general characteristicsof the flow. Previous studies have also simulated transient behavior and flow features effectingbreakup of fuel flowing through a swirl injector.A steady state simulation using Volume of Fluid (VOF) multiphase modeling and $k$-$\omega$ \emph{SST}turbulence modeling was used to simulate the swirl injector intended for the rocket engine. It wasfound that a wider outlet orifice would give a wider cone angle of spray. This is desirable in thecurrent rocket engine design as it will promote greater mixing of fuel and oxidizer higher up in thecombustion chamber. No large variances was observed when different inlet slot angles was simulated. Ashorter swirl chamber length reduced the amount of losses in energy due to viscous forces. The flowafter the outlet orifice was not simulated so the effect of turbulence kinetic energy and energylosses outside of the swirl injector have not been analyzed, previous studies have indicated thatturbulent kinetic energy does have an effect on the breakup and atomization of the fuel.It was concluded that using a wider outlet orifice of 9 mm gave the best results out of the differentgeometric parameters analyzed and the swirl chamber length should be a short as possible.

To better understand how platelets behave when exposed to high shear stress, computational fluid dynamic (CFD) models for single-layer (uniform and constant) viscosity flow and two-layer (two distinct regions of different viscosities) viscosity flow were developed. The single-layer model, which represents common standard practice, did not predict the pressure drop correctly; the error produced from using the single-layer model was approximately 95%. However, the two-layer model produced results that were within 6% of the experimental results. Experimental results used to validate CFD models were obtained from data gathered by researchers at University Medical Center (UMC) in Jackson, MS. Using Fluent 6.2, simulations were performed that showed the characteristics of blood flow in a long stenosis. The beginning of the development of a blood damage model was also investigated. This thesis could provide researchers with information that will eventually allow the prediction of platelet activation and hemolysis.

Simulations were performed to evaluate solution adaptive meshing strategies for flows with vortices whose axes of rotation are parallel to the bulk fluid motion. Two configurations were investigated: a wing in a wind tunnel and a missile spinning at 30Hz and 60Hz at 0◦ angle of attack with canards deflected 15◦. Feature-based descriptors were used to identify regions of the flow near vortices that are candidate regions for adaptive meshing. Several different adaptive meshing techniques were evaluated. These techniques include refinement around the vortex core, refinement near the vortex extent surface, refinement inside the extent surface, refinement inside and near the extent surface, and mesh regeneration using the vortex extent surface as an embedded surface. Results for the wing case, compared to experimental data, indicate that it is necessary to refine the region within and near the vortex extent surface to accurately recreate physical characteristics and achieve an acceptable solution.

<p>Lubrication and friction of modern rolling element bearings were investigated to develop a physics-based bearing friction model. A test rig was designed and developed to measure the frictional torque of radially loaded rolling element bearings with oil bath lubrication. Deep groove ball bearings and radial needle roller bearings were studied at various loads, speeds and lubrication conditions. Experimental results indicate that bearing friction models currently used in industry can be inaccurate, especially when predicting bearing fluid drag losses. A separate test rig was designed and developed to investigate the lubrication and friction of rolling element bearing cage pockets, as new cage pocket designs could improve bearing efficiency. Cage pocket oil starvation was observed for certain operating conditions, and the starvation was found to correlate strongly with cage pocket friction. In order to better understand friction and lubrication characteristics of bearings, computational fluid dynamics (CFD) models were developed to compare with the experimental results. Fluid motion inside the rolling element bearings was investigated using CFD to determine fluid drag torque of bearing components. Fluid drag torque obtained from CFD and experimental measurements are in good agreement. Results from the CFD models also included pressure distributions over bearing surfaces and fluid velocity near rolling elements, but were limited to global length scales. At the micro-scale, rolling element bearing lubrication and friction is dictated by elastohydrodynamic lubrication (EHL). The radial needle roller bearings and deep groove ball bearings used in this investigation are characterized by line and elliptical contacts, respectively. EHL modeling was therefore developed for line contacts with a strongly coupled fluid solid interaction (FSI) solver. Solid bodies were modeled with finite element (FE) software to incorporate inhomogeneities such as inclusions and surface features which affect EHL pressure, film thickness and friction. Results were used to investigate lubricant film thickness at lubricated line contacts under various operating conditions. This work was further extended to model EHL circular contacts with an FSI approach, combining CFD and FE software. The newly developed FSI EHL model provided critical insights regarding fluid behavior in and around EHL point contacts and fluid properties within the lubricant film. Given the modeling results at the micro and macro scale within the rolling element bearings, a better understanding of bearing friction and lubrication is developed, and supported by experimental data.</p>

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