Numerical Investigation Of Vortex Generator Flow Control For External-Compression Supersonic Inlets, Ezgihan Baydar

Mechanical and Aerospace Engineering Dissertations - Archive

Vortex generators (VGs) within external-compression supersonic inlets for Mach 1.6 were investigated to determine their ability to increase total pressure recovery and reduce total pressure distortion. Ramp and vane-type VGs were studied. The geometric factors of interest included height, length, spacing, angle-of-incidence, and positions upstream and downstream of the inlet terminal shock. The flow through the inlet was simulated numerically through the solution of the steady-state, Reynolds-averaged Navier-Stokes equations on multi-block, structured grids using the Wind-US flow solver. The inlet performance was characterized by the inlet total pressure recovery and the radial and circumferential total pressure distortion indices at the …

Development Of An Emulated Free-Floating Environment For On-Earth Testing Of Space Robots, Narendran Muraleedharan

Doctoral Dissertations and Master's Theses

The ability to perform experiments on space robotic systems within a laboratory setting is crucial to development and testing of satellites and space robots prior to launch. One of the most widely used techniques which recreate the on-orbit motion of space robots and targets is hardware-in-the-loop simulation. This method requires extensive knowledge of the space robot model dynamic parameters. This research proposes a method which uses force feedback to control a robotic platform on which the space robot is mounted. The robotic platform is driven in such a way that the gravity-compensated forces and torques at the mounting interface are …

Ab Initio Computation Of Radiative Properties Of Monatomic Hydrogen, Fanny Thomas

Doctoral Dissertations and Master's Theses

With renewed interest in planetary atmospheric entry, descent, and landing, NASA has noted a need for improved physics modeling in computational fluid dynamics. Uncertainty in experimental data used in radiation heat transfer computations leads to “over-engineering” of entry body heat shields, at large weight and cost penalties. There is interest in developing hypersonic thermophysics models from the known “first principles” of physics.

A method for computing high temperature gas emissivity and absorptivity from quantum mechanics principles is developed. The Schroedinger wave equation is cast as a discretized matrix eigenvalue problem which is solved using the ERAU parallel supercomputer. The numerical …

Fast Neutron Detection In Nuclear Material Photofission Assay Using A 15 Mev Linear Electron Accelerator, Matthew Steven Hodges

UNLV Theses, Dissertations, Professional Papers, and Capstones

The purpose of this research was to use a 15 MeV (K15 model by Varian) linear electron accelerator (linac) for the photon assay of special nuclear materials (SNM). First, the properties of the photon radiation probe were determined. The stochastic radiation transport code, MCNP5, was used to develop computational models for the linac. The spectral distribution of photons as well as dose rate contour maps of the UNLV accelerator facility were computed for several linac operating configurations. These computational models were validated through comparison with experimental measurements of dose rates.

The linac model was used to simulate the photon interrogation …

Analytic Solutions For The Crack-Tip Plastic Zone Under Mixed Mode Loading Conditions, Jason Ivey

Mechanical Engineering ETDs

Analytic solutions for the plastic region surrounding a crack tip are derived under mixed mode I/II and mixed mode I/II/III loading conditions for an elastic-plastic solid with a semi-infinite crack. Both the Von Mises and Tresca yield criteria are applied. Additionally, plane stress and plane strain assumptions are included when applicable. The results show a strong dependence on the ratio of the stress intensity factors for each loading mode. It is shown that the plastic zone area given by the Tresca yield criterion is larger than that given by the Von Mises yield criterion. Lastly, it is investigated whether or …

Chip-Package Interfacial Stress Analysis And Reliability Implications For Flip-Chip Power Devices, Jonathan Gh Treco

Mechanical Engineering Undergraduate Honors Theses

The solder in flip-chip assemblies experience high stress and strain because of thermal mismatch induced deformation. These deformations occur because of the differences of coefficient of thermal expansion between flip-chip assembly materials. The similarly in stress profiles between thermal induced and shear induced stress in solder joints enable the use of die shear testing as a representative technique for relating the max stress the flip-chip can withstand to cyclic thermal fatigue failures. In this work, two electronic device sample preparation types are evaluated: One set of samples are soldered together and other set of samples use epoxy as an adhesive. …

System-Layout-Dependent Thermally Induced Solder Stress & Reliability Implications, Ange C. Iradukunda

Mechanical Engineering Undergraduate Honors Theses

Electronic flip chip assemblies consist of dissimilar component materials, which exhibit different CTE. Under thermal cyclic operating conditions, this CTE mismatch produces interfacial and interconnect stresses, which are highly dependent on system layout. In this paper, sensitivity analyses are performed using ANSYS FEA to establish how the proximity and arrangement of neighboring devices affect interconnect stress. Flip chip alignment modes ranging from edge-to-edge to corner-to-corner are studied. Results of these FEA studies, demonstrated that closely packing devices together has the effect of making them act as one. This results in a significant increase in the thermomechanical stresses induced on peripheral …

Determining Drag Forces On 3d Printed Shark Skin And The Conditions In Which Drag Forces Are Reduced, Kayla M. Bartnicke

Mechanical Engineering Undergraduate Honors Theses

ABSTRACT

This project was conducted at the University of Arkansas with access to 3D printers and a water tunnel. The project examines drag forces over 3D-printed shark skin. Shark skin was chosen to be studied because of its unique three-pronged denticle shape and the assumption that this unique shape has a purpose, such as drag reduction.

A shark denticle was designed using SolidWorks software, multiplied 164 times creating a total skin area of 17.5 in², and printed using both a MakerBot Replicator 2 3D printer and an Ultimaker 2 Go 3D printer. The shark skin was initially printed …

Modeling Three Dimensional Ground Reaction Force Using Nanocomposite Piezoresponsive Foam Sensors, Parker Gary Rosquist

Theses and Dissertations

Three dimensional (3D) ground reaction force (GRF) are an essential component for gait analysis. Current methods for measuring 3D GRF involve using a stationary force plate embedded in the ground, which captures the forces as subjects walk across the platform. This approach has several limitations, a few being: it can only capture a few steps at a time, it is expensive to purchase and maintain, it can't reflect forces caused by natural uneven surfaces, etc. Previous research has attempted to develop wearable force sensors to overcome these problems; however, these endeavors have resulted in devices that are expensive, bulky, and …

Integration Of A Complete Detect And Avoid System For Small Unmanned Aircraft Systems, Jared Kevin Wikle

Theses and Dissertations

For unmanned aircraft systems to gain full access to the National Airspace System (NAS), they must have the capability to detect and avoid other aircraft. This research focuses on the development of a detect-and-avoid (DAA) system for small unmanned aircraft systems. To safely avoid another aircraft, an unmanned aircraft must detect the intruder aircraft with ample time and distance. Two analytical methods for finding the minimum detection range needed are described. The first method, time-based geometric velocity vectors (TGVV), includes the bank-angle dynamics of the ownship while the second, geometric velocity vectors (GVV), assumes an instantaneous bank-angle maneuver. The solution …

Cfd Analysis Of Resistance Characteristics Of High-Speed Displacement Hull Forms Fitted With Hull Vane®, Venkata Karthik Avala

Theses and Dissertations

Improving the performance and resistance of a high-speed monohull forms has been of interest to Naval Architects for several decades. A considerable amount of research has been carried out in this area by using stern flaps and other appendages. This research thesis investigates the resistance characteristics of high-speed round bilge hull forms fitted with a Hull Vane® in the stern region of the vessel. The Hull Vane® is a fixed foil located below the waterline at the aft of the stern of the vessel. The Hull Vane® reduces the generation of waves at the aft and improves the vessel's motions. …

Supervisory Controls Strategy To Reduce Utility Factor Weighted Criteria Emissions For A Plug-In Hybrid Electric Vehicle, Thomas Francis Gorgia Iii

Doctoral Dissertations and Master's Theses

Criteria emission reduction techniques are being more sought out in the automotive industry due to current government regulation for light duty vehicles. Parallel-series plug in hybrid electric vehicles can have multiple strategies to balance emissions and fuel consumption. Common controls strategies in industry target fuel economy by using a large electric vehicle range, known as charge depletion, followed by maintaining a state of charge after a specific vehicle threshold, or charge sustaining. A charge preserve strategy works by running an engine at an optimal loading condition, the engine will burn the fuel more complete reducing criteria emissions. Charge preserve will …

Discrete Element Analysis Of Scb Variability: Asphalt Mixtures, David Saul Renteria

Theses and Dissertations

The Semi-Circular Bending (SCB) test was modeled using the Discrete Element Method (DEM) implemented in numerical software Particle Flow Code (PFC). The fracture analysis of the SCB was studied using two mixtures gradation, Superpave and Coarse Matrix High Binder. The aggregate phase in the model was achieved by using two-dimensional aggregate images with different angularity indexes. The study of the variability of the SCB extends to the random generation of aggregate particles and air voids in the model, in addition to changing the properties at the interface between the aggregate and mastic phases. Results indicate the strong influence of the …

The Development Of A Vacuum Forming System For Kydex® And Other Thermoplastic Sheet, Andrew G. Smith

Electronic Theses and Dissertations

Vacuum forming is a popular, cost effective method amongst large and small scale applications. The method is used to mold a material to the surface of a mold/pattern in order to create a negative copy for reproduction or an object in positive form. The prototype vacuum forming system developed and documented herein is of a membrane-seal type that consists of three (3) principle parts: radial platen, Hinged Frame and Platen Support Assembly, and a PVC surge tank. Each part is described in detail through design, manufacturing, and testing processes. The design supports functional versatility, small scale molding, and uses readily …

Dynamics Of Asymmetrical Configurations Of Catamaran Hull Forms, Vaibhav Aribenchi

Theses and Dissertations

It is important to understand asymmetrical catamarans motions since it influences the loads which increases stress on structures while causing discomfort to passengers and crew members. Researchers so far have been mainly focused on motions characteristics of the conventional catamaran hull forms. There is scant literature or research work in the public domain on asymmetrical catamaran hull form, with regards to its seakeeping performance. This thesis undertakes a comparative analysis of the motion characteristics between newly developed alternative catamaran hull forms of different asymmetrical configurations. The asymmetrical catamarans developed from the original NPL round bilge catamaran hull forms have a …

An Empirical Examination Of Cognitive Chunking And Information Generation In Freehand Sketches During Design Ideation, Omar Magdy Ibrahim Zaki Mohammed Galil

Theses and Dissertations

This thesis proposes a method to measure information content of freehand sketches during design ideation based on the cognitive chunk formation. The research is broken down into two phases. The first is a protocol study to explore chunk formation in freehand sketches by novice designers while generating solutions for a novel design problem. The second is the identification of entities and functional relations explicitly expressed in the designers’ output. Next, a form neutral (F-ER) representation model is formulated, and information metrics are applied to measure the information content. This work is motivated by the notion that engineering design can be …

Dynamic Anchoring In Soft Regolith For Celestial Exploration, Tom Ebert

Theses and Dissertations

Recent exploration missions to celestial bodies have shown an increasing demand for surface based landers and rovers designed to perform experiments on the ground, rather than relying purely on traditional orbiting observatories. Many of the scientifically interesting locations have proven hazardous and difficult to reach and traverse, driving the need for different methods of locomotion. Some of these locations lie in deep, permanently shadowed craters or in rocky, highly uneven landscapes. Various wheeled, flying, jumping and legged rovers have been proposed, some of which have been implemented with success and problems alike. Even though the Curiosity rover has the largest …

Numerical Investigation Of A Phase-Change Material Based Photovoltaic Panel Temperature Regulation System, Rohit Gulati

Doctoral Dissertations and Master's Theses

As the production of clean electricity has gained importance, photovoltaic (PV) panels have become a widely used technology. But, during operation, PV panels heat up due to the solar insolation and suffer a drop in electrical output. The goal of this investigation is to use phase-change materials (PCM) to passively cool PV panels. The PCM is inside an aluminum container attached to the back surface of the PV panel. Four configurations of the container are investigated. The first configuration is a container with bulk PCM occupying its entire interior volume. The depth of this container is varied. The second configuration …

Casimir And Van Der Waals Effects On Electrostatically Actuated Nems Resonator Sensors, Christian Reyes

Theses and Dissertations

The behavior of nano and micro-electromechanical systems (N/MEMS) cantilever beams under electrostatic actuation is studied. The cantilever system is actuated by soft AC voltage that is set to a frequency of near half natural and near natural frequency of the beam. These actuating frequencies result in primary and parametric resonances, respectively. Two methods are used to analytically model the behavior of the cantilever. The first method is Method of Multiple Scales (MMS), which is a perturbation method that works for small parameters. The second method is the Reduced Order Method (ROM), which is a Galerkin method that works for large …

Design And Implementation Of A Pid Controller For The Low-Speed Wind Tunnel, Carlos F. Vasquez

Theses and Dissertations

The purpose of this research is to investigate the implementation of an external PID controller on an existing variable frequency motor drive (VFD) while using MODBUS communication to read/write data from a LabVIEW station. LabVIEW is the chosen user interface and programming language. It allows human-machine interfacing for the collecting, displaying of information, and automation of the system. The main objective was to develop a new controller to facilitate the operation of the wind tunnel. The current setup makes the operator set the motor frequency manually which then correlates to a test section wind velocity. This involved a calibration period …

Automation In Entertainment: Concept, Design, And Application, Ryan Thally

Undergraduate Honors Theses

The focus of this thesis is to explore the automation technology used in the modern entertainment industry. Upon completion of my thesis, I will deliver a working prototype of the chosen technology and present its capabilities in a choreographed show.

Refurbished And 3d Modeled Thermal Vacuum Chamber, Lauren M. Glenn

Master's Theses

Spacecraft testing includes acoustics, vibrations, and thermal vacuum. Cal Poly’s Space Environments Lab is equipped with multiple vacuum chambers, but no thermal vacuum chamber. The purpose of this thesis is to incorporate an ATS Chiller system with the HVEC vacuum chamber so students are able to experiment with a thermal vacuum chamber. The ATS Chiller had leaky pipes that needed to be refurbished and a shroud was implemented to improve thermal capabilities of the system. The full system was able to reach temperatures as low as -38ºC and as high as 58ºC at a pressure of 10-6 Torr. The ATS …

Supercritical Carbon Dioxide Extraction, Kevin Carney

Master's Theses

The objective of this thesis is to explore the properties of supercritical carbon dioxide (CO₂). In addition, the feasibility of building a small-scale low cost system will be explained. A supercritical fluid is a fluid which exhibits properties between liquid and gas with liquid like densities and viscosities similar to a gas. Since the discovery of supercritical fluids in 1822, the use of supercritical fluids, specifically supercritical CO₂, has grown in popularity. The application of supercritical CO₂ has continued to grow in industrial applications since the 1970’s. Supercritical CO₂’s has many beneficial properties …

Electromagnetic Design Of A Superconducting Twin Axis Cavity, S. U. De Silva, H. Park, J. R. Delayen, F. Marhauser, A. Hutton

Physics Faculty Publications

The twin-axis cavity is a new kind of rf superconducting cavity that consists of two parallel beam pipes, which can accelerate or decelerate two spatially separated beams in the same cavity. This configuration is particularly effective for high-current beams with low-energy electrons that will be used for bunched beam cooling of high-energy protons or ions. The new cavity geometry was designed to create a uniform accelerating or decelerating fields for both beams by utilizing a TM₁₁₀ dipole mode. This paper presents the design rf optimization of a 1497 MHz twin-axis single-cell cavity, which is currently under fabrication.

Design Baseline Document: Mini Baja Frame, Michael Luke Scoggins

Undergraduate Honors Capstone Projects

Our objective as the Mini Baja Frame team is to design and implement a prototype vehicle frame that is both cost-effective and competitive in an all-terrain racing environment. This vehicle must be able to endure the trials of the Society of Automotive Engineers (SAE) Mini Baja competition. An effective frame will contribute to the complete Utah State University Mini Baja Team objectives by efficiently integrating the components produced by the drivetrain and the suspension engineers. In addition, this competition is a means for us as students to gain valuable, tangible experience in the engineering design process.

Applications Of Relative Motion Models Using Curvilinear Coordinate Frames, Alex C. Perez

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A new angles-only initial relative orbit determination (IROD) algorithm is derived using three line-of-sight observations. This algorithm accomplishes this by taking a Singular Value Decomposition of a 6x6 matrix to arrive at an approximate initial relative orbit determination solution. This involves the approximate solution of 6 polynomial equations in 6 unknowns. An iterative improvement algorithm is also derived that provides the exact solution, to numerical precision, of the 6 polynomial equations in 6 unknowns. The initial relative orbit algorithm is also expanded for more than three line-of-sight observations with an iterative improvement algorithm for more than three line-of-sight observations. The …

Evaluation Of Flux Correction On Three-Dimensional Strand Grids With An Overset Cartesian Grid, Dalon G. Work

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Simulations of fluid flows over complex geometries are typically solved using a solution technique known as the overset meshing method. The geometry is meshed using grid types appropriate to the local geometry in a patchwork fashion, rather than meshing the entire geometry with one type of mesh. The strand-Cartesian approach is a simplification of this process. While high-order accurate solvers on Cartesian grids are simple to implement, strand grids are usually restricted to second-order accuracy, resulting in poor quality solutions. Flux correction is a high-order accurate solution method, specifically designed for use on strand grids. The flux correction method on …

Characterization Of The Thermal Resistance Of Grain Boundaries Of Cerium Oxide, Jesse Spackman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Many materials are made up of small crystals, or grains. Grain boundaries are the interfaces between two grains and affect the flow of heat through the material. These interfaces serve to interfere with the energy carriers by scattering or disrupting them. Because of the negative effect these interfaces have on these energy carriers, they inhibit heat flow and act as thermal resistors. The thermal boundary resistance between two grains of the same material is sometimes referred to as the Kapitza resistance, although this term is also used to describe the thermal resistance between solid/solid interfaces of different materials or solid/liquid …

Water Entry Impact Dynamics Of Diving Birds, Saberul Islam Sharker

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Plunge diving and surface diving are two main techniques used by seabirds for foraging purposes. While some plunge divers can dive into the water at very high speeds (24 m/s), surface divers do not. This study analyzes the free-surface impact of 3D printed bird head models with embedded accelerometers to determine why surface divers cannot dive safely at high speeds. The problem is investigated in the context of impact jerk where surface divers, unlike plunge divers, are found to experience non-dimensional jerk (J^∗) values exceeding a safe limit. This approach portrays itself as an unconventional yet effective method …

Effects Of Computer Simulation And Animation (Csa) On Students’ Problem Solving In Engineering Dynamics: What And How, Seyed Mohammad Tajvidi

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Previous studies have shown that in many fields, computer simulation and animation (CSA) improve students’ learning and problem solving. However, despite the massive body of research on the role of computers in education, little research has been conducted to qualitatively examine how they affect the learning of engineering students. The purpose of this study was to explore how learning and problem solving were affected by computer modules and what similarities and differences existed between computer representations and paper-based examples.

An analysis of collected data, observations of participants’ problem-solving activities, and interviews revealed that computers can enhance students’ analytical thinking, organizing, …