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Full-Text Articles in Mechanical Engineering

Streamwise Flow-Induced Oscillations Of Bluff Bodies - The Influence Of Symmetry Breaking, Tyler Gurian Jan 2018

Streamwise Flow-Induced Oscillations Of Bluff Bodies - The Influence Of Symmetry Breaking, Tyler Gurian

Masters Theses

The influence of symmetry breaking on the flow induced oscillations of bluff bodies in the steamwise direction is studied. First, a series of experiments is conducted on a one-degree-of-freedom circular cylinder allowed to exhibit pure translational motion in the streamwise direction over a range of reduced velocities, 1.4 < U* < 4.4, corresponding to a Reynolds number range of 970 < Re < 3370. Two distinct regions of displacements were observed in reduced velocity ranges of 1.6 < U* < 2.5 and 2.75 < U* < 3.85. Measured force coefficients in the drag and lift direction were examined, along with the wake visualization, through the range of reduced velocities, to infer the resulting wake modes. A new Alternating Symmetric (AS) mode was found. This transition from symmetric to AS shedding occurred near the end of the first region of response. Similar tests were run with a square prism in the parameter space of 2.4 < U* < 5.8 and 757 < Re < 1900 over angles of incidence of 0° ≤ α ≤ 45°. A distinct region of lock-in is observed for α = 0°, 2.5°, 5°, 7.5° over 3.2 < U* < 5.4 for α = 0°, and decreasing with increasing α. The wake structures were found to be roughly symmetric for α = 0°, but transitioned towards asymmetry with ...


A Numerical Flutter Predictor For 3d Airfoils Using The Onera Dynamic Stall Model, Pieter Boersma Jan 2018

A Numerical Flutter Predictor For 3d Airfoils Using The Onera Dynamic Stall Model, Pieter Boersma

Masters Theses

To be able to harness more power from the wind, wind turbine blades are getting longer. As they get longer, they get more flexible. This creates issues that have until recently not been of concern. Long flexible wind turbine blades can lose their stability to flow induced instabilities such as coupled-mode flutter. This type of flutter occurs when increasing wind speed causes a coupling of a bending and a torsional mode, which create limit cycle oscillations that can lead to blade failure. To be able to make the design of larger blades possible, it is important to be able to ...


Electroplating Of Copper On Tungsten Powder, Richard Berdos Jan 2018

Electroplating Of Copper On Tungsten Powder, Richard Berdos

Masters Theses

Strengthening, resistant and shielding properties, to name a few, can be achieved by implementing a surface material coating onto an engineering component. Various elements of these compounded parts can augment the functionality of the part, such as, increased life time and more interactive surfaces. Tungsten has proven to be a challenge to plate with other metals, but if done correctly, the results can allow for the cold spray of tungsten. Cold spraying tungsten particles alone provides a challenge because the powder is too hard and instead of adhering, it erodes the surface it is attempting to plate. Coating tungsten in ...


Non-Equispaced Fast Fourier Transforms In Turbulence Simulation, Aditya M. Kulkarni Jan 2017

Non-Equispaced Fast Fourier Transforms In Turbulence Simulation, Aditya M. Kulkarni

Masters Theses

Fourier pseudo-spectral method on equispaced grid is one of the approaches in turbulence simulation, to compute derivative of discrete data, using fast Fourier Transform (FFT) and gives low dispersion and dissipation errors. In many turbulent flows the dynamically important scales of motion are concentrated in certain regions which requires a coarser grid for higher accuracy. A coarser grid in other regions minimizes the memory requirement. This requires the use of Non-equispaced Fast Fourier Transform (NFFT) to compute the Fourier transform, by solving a system of linear equations.

To achieve similar accuracy, the NFFT needs to return more Fourier coefficients than ...


Incorporating Seasonal Wind Resource And Electricity Price Data Into Wind Farm Micrositing, Timothy A. Pfeiffer Jan 2017

Incorporating Seasonal Wind Resource And Electricity Price Data Into Wind Farm Micrositing, Timothy A. Pfeiffer

Masters Theses

Currently, most micrositing techniques aim to maximize annual energy production (AEP) or minimize cost of energy (COE) with no direct regard to revenue. This research study developed a method that utilizes the seasonal electricity price and wind data to microsite wind farms in terms of profitability. To accomplish this, six candidate wind farms with differing layouts and spacing were selected at a given location. They were then simulated using a wake modeling software to produce expected power outputs at different wind speeds, wind directions, and turbulence intensities. By interpolating the power output tables with wind data, a power time-series was ...


Electroless Deposition & Electroplating Of Nickel On Chromium-Nickel Carbide Powder, Jeffrey Rigali Jan 2017

Electroless Deposition & Electroplating Of Nickel On Chromium-Nickel Carbide Powder, Jeffrey Rigali

Masters Theses

Engineered components can gain desirable properties when coated with surface materials. Wear-resistant coatings can improve the performance of contacting surfaces and allow for an extended life of the parts. Hard chromium has been the plating material of choice for certain wear and corrosion- resistant coatings because of its desirable combination of chemical resistance, adhesion, and mechanical properties. However, hexavalent chromium, a component of the process for applying hard chromium coatings, has been recognized by the EPA as having hazardous health and environmental impacts. Existing and planned environmental regulations restricts the use of process chemicals containing hexavalent chromium ions. This substantiates ...


Tracking Of Human Joints Using Twist And Exponential Map, Xiaodong Yang Dec 2016

Tracking Of Human Joints Using Twist And Exponential Map, Xiaodong Yang

Masters Theses

Motion tracking system in the home-based environment exhibits attractive advantages for stroke patients. Current methods suffer from incapability of accurately tracking movements with high degree of freedoms. Besides hardly meeting the predefined position during inertial sensor mounting also affects system's performance.

To tackle these challenges, a motion tracking system using twist and exponential map technology is developed in this paper. Firstly, a kinematic model for trunk and upper extremity is designed. Based on this model, twist and exponential map method which updates frames in their initial coordinates instead of transforming coordinates from one frame to another presents high efficiency ...


Dynamic Monitoring And Life Prediction Of Internal Strain-Gage Balances, David Leon Yoder Dec 2016

Dynamic Monitoring And Life Prediction Of Internal Strain-Gage Balances, David Leon Yoder

Masters Theses

Wind tunnel test customers continue to push the limits by producing air vehicle designs that produce high aerodynamic loads at the desired test conditions. These loads are a combination of steady aerodynamic, unsteady aerodynamic, and inertial forces. A methodology to monitor the health of a wind tunnel strain-gage balance has been developed. The objective of this methodology is to define the stress limits of the balance and monitor these limits so the balance can be safely tested without failure of the balance. A balance failure could result in costly damage to the wind tunnel model, support system, and the wind ...


Jet Flow Validation Of Positron Emission Particle Tracking Utilizing High Speed Video, Seth Thomas Langford May 2016

Jet Flow Validation Of Positron Emission Particle Tracking Utilizing High Speed Video, Seth Thomas Langford

Masters Theses

Positron Emission Particle Tracking (PEPT) generates 4D Lagrangian particle trajectories and is used to evaluate flow in granular media and complex geometries where optical interrogation methods are not possible. A Multi-Particle PEPT (Multi-PEPT) approach was developed by the University of Tennessee Thermal Fluids Group capable of finding and tracking many particles simultaneously to extend the utility of the PEPT method. This thesis compares 4,014 trajectories generated using the Multi-PEPT method with 3,055 trajectories generated from High Speed Video (HSV) data. All trajectories are acquired in an acrylic test section with water flow using resin beads. The flow geometry ...


Numerical Simulation Of High Velocity Impact Of A Single Polymer Particle During Cold Spray Deposition, Sagar P. Shah Jan 2016

Numerical Simulation Of High Velocity Impact Of A Single Polymer Particle During Cold Spray Deposition, Sagar P. Shah

Masters Theses

Abstract

The cold spray process is an additive manufacturing technology primarily suited for ductile metals, and mainly utilized in coating surfaces, manufacturing of freeform parts and repair of damaged components. The process involves acceleration of solid micro-particles in a supersonic gas flow and coating build-up by bonding upon high velocity impact onto a substrate. Coating deposition relies on the kinetic energy of the particles. The main objective of this study was to investigate the mechanics of polymer cold spray process and deformation behavior of polymers to improve technological implementation of the process.

A finite element model was created to simulate ...


Evaluation Of Fuel Flow Measurement Uncertainty In A Turbine Engine Test Cell, Paul Andrew Wright Dec 2015

Evaluation Of Fuel Flow Measurement Uncertainty In A Turbine Engine Test Cell, Paul Andrew Wright

Masters Theses

The evaluation of measurement uncertainty is an essential part of measurement and data analysis. Measurement uncertainty is itself a measure of the “goodness” of the measured data and helps the analyst to make decisions based on the data. In the turbine engine testing world, accurate measurement of fuel flow is critical. Specific fuel consumption is a combination of thrust and fuel flow and is used to calculate the allowable payload and range of an aircraft as well as the cruising speed. Naturally, test customers (engine manufacturers, aircraft designers, and operators) are very sensitive to the accuracy of fuel flow measurement ...


Buckling Of Particle-Laden Interfaces, Theo Dias Kassuga Jan 2014

Buckling Of Particle-Laden Interfaces, Theo Dias Kassuga

Masters Theses

We study the buckling of an oil-water interface populated by micron-sized latex particles using a Langmuir trough. We extend pre-existing results to the micron-range with different capillary length and compare the experimental data to the existing theoretical framework. An unexpected trend for the dominant wavelength of buckling is observed, suggesting that there is a transition between regimes in the micron-range. A mechanism for the new regime is proposed. Cascading is reported, as well as novel kinds of transition between wavelengths within the same particle raft. Lastly, the effect of compression on the macroscopic arrangement of particles is investigated, as well ...


Water Transport In Polymer Electrolyte Fuel Cells: An Exploration Of Net Water Drag In Real Time, Susan Katherine Reid May 2013

Water Transport In Polymer Electrolyte Fuel Cells: An Exploration Of Net Water Drag In Real Time, Susan Katherine Reid

Masters Theses

Polymer electrolyte fuel cells (PEFCs) are a promising alternative energy source. One challenge preventing widespread use of this technology is water management. A balance must be reached between providing sufficient water for membrane ionic conductivity while maintaining low enough water content to mitigate the reduction of available reaction sites in the cathode catalyst layer due to liquid water build up. Much exploration of this area of fuel cell research has been conducted, but the details of water transport in an operating fuel cell are not yet fully understood. The motivation of this work was to elucidate mass transport phenomena occurring ...


Neutron Imaging Of Lithium Inside A High-Temperature Heat Pipe, Eric Henry Kirchoff May 2013

Neutron Imaging Of Lithium Inside A High-Temperature Heat Pipe, Eric Henry Kirchoff

Masters Theses

Neutron imaging of a high-temperature Mo-Li [molybdenum-lithium] heat pipe has been performed to assess Li flow visualization. The high neutron attenuation cross section of Li allows for imaging inside the heat pipe shell structure, which has a lower value of neutron attenuation, making neutron radiography an ideal choice for characterizing Li movement.

The gravity assisted, cylindrical heat pipe was heated to 903oC [degree] using a wire resistance Mo heater operating under vacuum. This Mo-Li heat pipe is 35 cm long with a square internal geometry 2.2 cm per side, utilizing small corner radii as the wicking structure ...


Heat Transfer Analysis Via Rate Based Sensors, Jake Erik Plewa Dec 2012

Heat Transfer Analysis Via Rate Based Sensors, Jake Erik Plewa

Masters Theses

This work presents an integrated rate-based sensor and method for resolving the surface heat flux of a fundamental inverse heat conduction problem without numerical regularization or differentiation in a semi-infinite geometry that additionally accounts for thermocouple delay due to its intrinsic time constant. The sensor uses well-designed analog filters to directly regularize raw voltage data to eliminate the need for numerical regularization methods. The sensor can also be used in a series of well-designed voltage-rate interfaces that directly measure the voltages from in-depth thermocouples, which are used in conjunction with the thermocouple calibration curve to provide higher-time derivatives of the ...


Droplet Characterization In The Wake Of Steam Turbine Cascades, Adam Charles Plondke May 2012

Droplet Characterization In The Wake Of Steam Turbine Cascades, Adam Charles Plondke

Masters Theses

In low-pressure steam turbines, water droplet formation on the surfaces of stationary stator blades can lead to erosion on downstream turbine blades and other equipment. One property that affects the size of the droplets that are formed is the adhesive forces between the water and the surface of the stator blade. The adhesive forces hold the droplets to the surface where they may combine, forming increasingly larger droplets. Eventually, the aerodynamic forces will tear the droplets off the surface, carrying them downstream.

To study the effect of stator surface properties on the droplet size distribution, four cascades of stator blades ...


A Method For Performance Analysis Of A Ramjet Engine In A Free-Jet Test Facility And Analysis Of Performance Uncertainty Contributors, Kevin Raymond Holst May 2012

A Method For Performance Analysis Of A Ramjet Engine In A Free-Jet Test Facility And Analysis Of Performance Uncertainty Contributors, Kevin Raymond Holst

Masters Theses

Ramjet and scramjet engines are being developed to provide a more fuel efficient means of propulsion at high Mach numbers. Part of the development of these engines involves test and evaluation of an engine in ground facilities as well as in flight. Ground facilities, like Arnold Engineering Development Center (AEDC) and those at engine manufacturers like General Electric (GE) and Pratt & Whitney (PW), have decades of experience testing traditional turbine engines and much less experience testing full scale ramjet engines.

Testing a supersonic engine model in a free-jet mode presents a host of challenges not experienced during traditional direct connect ...


Test Size And Volume Effects On Fatigue Behavior Of Bulk Metallic Glasses (Bmgs), Qingming Feng May 2012

Test Size And Volume Effects On Fatigue Behavior Of Bulk Metallic Glasses (Bmgs), Qingming Feng

Masters Theses

As a potential structural material, performance of bulk metallic glasses (BMGs) under cyclic loading is critical in applications. Among the mechanical properties of metallic glasses, the fatigue behavior received less attention and is not well understood. BMGs exhibit significant size effects on the mechanical behavior under monotonic loading, such as compression, tension, and bending. At the same time, different test-volume could lead to a distinct difference in the mechanical behavior of BMGs.

The fatigue behavior of the Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 [atomic percent (at. %)] BMG alloy (Vitreloy 105) with ...


Thermocouple Temperature Measurements For Twin Jet Thermal Mixing, Spero Michael Peters Dec 2011

Thermocouple Temperature Measurements For Twin Jet Thermal Mixing, Spero Michael Peters

Masters Theses

Thermocouples are commonly used devices for temperature measurement. This study concerns the implementation of thermocouples to collect thermal mixing data in an environment in which two parallel water jets are mixing. The measurements are taken with the purpose of modeling the jet mixing region so that Computational Fluid Dynamics (CFD) models can be validated against the test data. This thesis covers the design, construction, implementation and evaluation of a thermocouple system for immersion in a water environment to measure the thermal mixing of twin jets.

The measurement system being used is a thermocouple rake whose design and fabrication is covered ...


Residential Attic Ventilation In A Hot And Humid Climate: Effects Of Increased Ventilation On Thermal Performance And Moisture Control, Stanley Arthur Atherton Dec 2011

Residential Attic Ventilation In A Hot And Humid Climate: Effects Of Increased Ventilation On Thermal Performance And Moisture Control, Stanley Arthur Atherton

Masters Theses

The reality of the effect of natural ventilation in a residential attic cavity has been the topic of many debates and scholarly reports since the 1930’s. The purpose of ventilating an attic cavity is to prevent collection of condensate on the structural surfaces, and to create a thermal buffer between the conditioned space and the ambient air. The current standards are not specific to climate zone, despite the fact that each climate zone may require ventilation for very different reasons.

To address the issue of ventilation effects in a hot and humid climate, a Natural Exposure Testing facility was ...


Effects Of Supercooled Water Ingestion On Engine Performance, Rick Hutchings Aug 2011

Effects Of Supercooled Water Ingestion On Engine Performance, Rick Hutchings

Masters Theses

An aircraft will encounter freezing rain, snow, and ice during ground operation and flight. In cold conditions, ice may form on th einlet and internal stators and rotors of the gas turbine engine. When ice accumulates on blades (and/or stators), the aerodynamic characteristics of the blades change due to the altered size, shape, and roughness. This change causes the blade to no longer operate at its design point and decreases compressor performance. Therefore, characterization of the aerodynamic performance is required to define the associated losses due to the effects of supercooled liquid water ingestion. This characterization can be accomplished ...


Effect Of Moisture Absorption On The Sinter Quality Of Central Solenoid (Cs) Coil Pack, Zeshaan Sher Mohammed Dec 2010

Effect Of Moisture Absorption On The Sinter Quality Of Central Solenoid (Cs) Coil Pack, Zeshaan Sher Mohammed

Masters Theses

Fusion energy has been said to be the solution to all the world’s energy problems. The International Thermonuclear Experimental Reactor (ITER) is the flagship project to demonstrate the feasibility of fusion energy. The Central Solenoid (CS), an important component of the reactor, is needed to induce plasma current, initiate, ramp-up, ramp-down, and sustain plasma in a very controlled manner. In order to achieve this, the CS coil packs must be manufactured under controlled conditions. The CS conductor is an advanced cable-in-conduit Nb3Sn superconductor. The CS cable will be made in long continuous sections but with thousands of meter of ...


Use Of A Press-Fit Grip Sleeve For Cable-In-Conduit Superconductor Integration: Effects Of Tensile And Fatigue Loading, Paul Michael Hayes Dec 2010

Use Of A Press-Fit Grip Sleeve For Cable-In-Conduit Superconductor Integration: Effects Of Tensile And Fatigue Loading, Paul Michael Hayes

Masters Theses

Presently, one of the most promising sources for a future of abundant, low-emission, and efficient energy comes in the form of nuclear fusion. However, in order for it to become a reality, fusion technology must overcome the obstacle of plasma confinement. Utilizing the tokomak based design for magnetic plasma confinement; ITER is currently developing a fusion reactor to prove its commercial viability.

The purpose of this research was to determine the feasibility of pulling toroidal field cable with a press-fit grip sleeve that utilizes friction to generate a gripping force. Such a design is being considered by ITER to integrate ...


Solid Target System For Use On An 11 Mev Cyclotron, Andrew Carl Williamson Dec 2010

Solid Target System For Use On An 11 Mev Cyclotron, Andrew Carl Williamson

Masters Theses

Molecular imaging is becoming an important contributor to the development of personalized medicine. Positron Emission Tomography (PET) is a technology that enables molecular imaging by allowing a physician to detect and map the location of various physiological processes. The purpose of this work is to design, fabricate and test a mechanism that would make the production of the PET isotope, copper-64 practical for both researchers and commercial suppliers. In order to have the maximum usefulness, the design needs to fit and operate within several constraints. A one dimensional thermal analysis indicated that operation of the system under existing cooling conditions ...