Engineering Commons^™

Convective Heat Transfer Enhancement Of A Channel-Flow Using Synthetic Jet, Pravesh Pokharel

Electronic Theses and Dissertations

A transient numerical simulation was carried out using ANSYS Fluent, to investigate the convection heat transfer enhancement of the air channel flow using the synthetic jet. Keeping the dimensional parameters of the domain fixed, averaged channel flow velocity was varied up to 3m/s. The diaphragm displacement effect on synthetic jet was studied, ranging the peak-to-peak displacement value from 0.4 to 1.2mm with increment of 0.4mm. Three locations were studied to determine the best operating location of the synthetic jet. Also, frequencies were varied up to 200Hz with every 50Hz increment, from initial condition of 50Hz. It was found that the …

Convective Heat Transfer Enhancement Of A Channel-Flow Using Horizontally-Oriented Piezoelectric Fans, Janak Tiwari

Electronic Theses and Dissertations

Experimental and numerical studies were carried out to investigate the convection heat transfer enhancement of air channel flow using a piezoelectric fan, operated at 90.3 Hz. Its peak-to-peak displacement was increased up to 11.8 mm. The average velocity of channel flow was ranged up to 3 m/s, covering both laminar and turbulent flow regimes. The effects of fan location on the heat transfer performance were evaluated by changing the relative position of the fan tip to the heated surface. A maximum heat transfer enhancement of 102 % was obtained at the channel flow rate of 15 LPM. The fan was …

Resonant Ultrasound Spectroscopy: Sensitivity Analysis For Anisotropic Materials With Hexagonal Symmetry, Christopher Lee Sevigney

Electronic Theses and Dissertations

Resonance ultrasound spectroscopy (RUS) is an experimental method by which material properties are obtained by careful observation of the resonant vibrations of a meticulously crafted sample. Among the most common applications of this technique is the determination of single-crystal elasticity. Previous works have considered the reliability of elasticity information obtained via the RUS method when the material is of isotropic or cubic symmetry, and this work extends these efforts to materials with hexagonal symmetry, such as titanium di-boride. The reliability of elasticity information obtained by RUS is evaluated by Sobol Analysis and by close examination of the stiffness-frequency functionality. Findings …

Nonreciprocity Applications In Acoustics And Microfluidic Systems, Masoud Naghdi

Electronic Theses and Dissertations

Breaking reciprocity in linear acoustic systems and designing a novel actuator for the nonreciprocal valveless pumps are studied in this dissertation. The first part was started by deriving the acoustic governing equations in a moving wave propagation medium. It was shown thatthe Coriolis acceleration term appears ina cross-product term with the wave vector. It means the main reason for breaking reciprocity in the circular fluid flow is the Coriolis acceleration term. Finally, the governing equations were solved numerically by COMSOL Multiphysics software. Moreover, Green`s second identity was used as a complimentary method to prove breaking reciprocityin such a system with …

Computational Modeling Of Shock Wave Propagation In A Layered Composites, Nicholas Ryan Scott

Electronic Theses and Dissertations

Modeling and simulation of a metallic flyer plate impacting a woven glass-fiber reinforced plastic (GRP) plate at different velocities was performed using the ALE3D© finite element code. The one-dimensional strain-based shock wave propagation experimental data in terms of time history of GRP’s back surface material particle velocity, available in open literature [1], were utilized in the calibration of a continuum damage mechanics (CDM) model. The experimental data included D7 Tool Steel and 7075-T6 aluminum flyer plates and two different GRP thicknesses (6.8 mm or 13.6 mm) with varying impact velocities in the range of about 8.5 m/s to 418 m/s. …

Molecular Dynamics Study Of Sintering Behavior Of Single-Crystal, Bimetallic Core/Shell Alloy, And Intermetallic Alloy Nanoparticles, Jungmin Jeon

Electronic Theses and Dissertations

There has been rapidly growing interest in the sintering process of nanoparticles (NPs) among academia and modern industry due to their promising applications in additive manufacturing (AM) based on the overall improved properties at nanoscale. In the past decade a lot of experimental and computational work has been conducted to study the sintering process of powder materials. However there is still a significant knowledge gap in a fundamental understanding of the thermodynamics and nanostructural evolution of NPs undergoing additive manufacturing. This thesis aims to gain fundamental insights into melting behavior of different materials including single-crystal bimetallic core/shell alloy and intermetallic …

Analytical Modeling And Life Cycle Assessment Of A Solar Powered Vapor Absorption Cooling System, Harold A. Walters

Electronic Theses and Dissertations

Vapor absorption cooling systems (VACS) offer an environmentally friendly alternative to the standard vapor compression cooling systems (VCCS) for cooling homes, businesses, factories, and other buildings. VACS use low-grade thermal energy to achieve a cooling effect and require minimal electrical input for the liquid solution pump used for circulation within the system. The thermal energy which powers these systems can be provided through several means; one popular form is through the use of solar thermal collectors. This paper provides a process for determining the overall size and configuration of the VACS depending upon the operating conditions of selected components. A …

Energy Harvesting Nanocoated Piezoceramics For Low Power Systems, Quinten Humphrey

Electronic Theses and Dissertations

No abstract provided.

Elastodynamic Model For Wind Induced Ground Motion, Mohammad Mohammadi

Electronic Theses and Dissertations

No abstract provided.

Mechanical And Computational Evaluation Of Cementitious Materials With Hollow Glass Microsphere Inclusions, Zachary J. Wallace

Electronic Theses and Dissertations

The effect of volumetric replacement of cementitious materials by an inert filler known as hollow glass microspheres on elastic properties is evaluated in this study through a combined computational and experimental approach. This approach considered the variation in properties of type I Portland cement for 0, 5, 10, and 15% volume fractions of two kind of glass microspheres; one was high density with high crushing strength, and the other with a relative lower density. Using a suite of software called Virtual Cement and Concrete Testing Laboratory (VCCTL), the microstructural details were determined for 80% degree of hydration of the cement …

Effect Of Vibration Of Unconsolidated Sand On The Performance Of Interferometric Vibration Sensors, Cody Berrey

Electronic Theses and Dissertations

Interferometric vibration sensors are widely used for ground vibration measurements where traditional contact sensors are not desired. Laser Doppler vibrometers (LDV) and digital speckle pattern interferometers are studied in this thesis. The working principle of laser Doppler vibrometry and digital shearography is described. The effect of vibration of the unconsolidated sand on the performance of both sensors is experimentally investigated.

The vibration of unconsolidated sand can cause an increase of noise in the laser Doppler vibrometer output and cause speckle decorrelation in digital speckle pattern interferometry (referred to as digital shearography). An experimental investigation of the effect of varying the …

A Study Of The Mechanical Behavior Of Composite Materials Exposed To Corrosive Environments, Ryan Keith Hedgepeth

Electronic Theses and Dissertations

A collaborative study was conducted to examine the degradation of commercially pultruded uni-directional e-glass composites. The case study specimens, including a variety of commercially pultruded polyester/e-glass and vinylester/e-glass composites were exposed to corrosive environments, namely: distilled water (h2o), bleach (naclo), and hydrochloric acid (hcl) for a minimum of 60 days, and the degradation was analyzed. Such a study was chosen on two accounts, 1) to contribute viable data to industry and research and 2) to provide data to be used to develop a standardized practice to characterize the durability for pultruded composites used for structural applications. A control group was …

Some Experimental Investigation On Effect Of Light And Vibration On Nano Coated Piezo For Energy Harvesting, Abhay Sharma

Electronic Theses and Dissertations

PZT is a promising piezoelectric ceramic material which has a wide range of applications in a variety of fields such as acoustic sensors and transducers, electrical switches, medical instrumentation, artificial sensitive skin in robotics, automotive detection on roads, nondestructive testing , structural health monitoring and as a biocompatible material. In this research a cantilever based multi energy harvester was developed to maximize the power output of PZT sensor. Nano mixtures containing graphene, ferrofluid nanoparticle (FNP) and ZnO nano particles were used to enhance the piezoelectric and photovoltaic output of the sensor. The samples were tested under different energy conditions to …

Temperature Dependence Of Shear Speed In Micellar Fluid, E.G. Sunethra Kumari Dayavansha

Electronic Theses and Dissertations

Wormlike micellar (WM) fluids are viscoelastic and can support shear waves. Phase transitions of the micellar aggregates are temperature dependent and can manifest as sharp changes in the shear wave speed as a function of temperature. Thus, shear waves provide a good tool for detecting the existence of phase transitions. In this work, the variation of shear speed with temperature of 200mM CTAB/NaSal micellar fluid in a 5:3 ratio was studied. The dependence of shear wave speed on time between fluid synthesis and measurement was also investigated. Shear wave propagation through the fluid was observed as a time varying birefringence …

Dynamic Mechanical Analysis And High Strain-Rate Energy Absorption Characteristics Of Vertically Aligned Carbon Nanotube (Vacnt) Reinforced Woven Fiber-Glass Composites, Kiyun Kim

Electronic Theses and Dissertations

No abstract provided.

Fiber Compaction And Wetout In Tapered Resin Injection Pultrusion Manufacturing, Naveen Babu Masuram

Electronic Theses and Dissertations

Pultrusion is a continuous process for manufacturing composite materials with constant cross section. Reinforced fibers are pulled through a resin, possibly folloby a separate injection chamber preforming system, and into a heated die, where the resin undergoes complete wetout. Thus the required pultruded composite is obtained in the desired profile. The main objective of this research is to present a numerical model employing the finite volume technique to simulate the resin flow in a tapered injection chamber through the fiber reinforcement when compaction of the fiber reinforcement is taken into account. The numerical model predicts the impact of design and …

Dynamic Response Of Glass Under Low-Velocity Impact And High Strain-Rate Compression Loading, Seyed Soheil Daryadel

Electronic Theses and Dissertations

In this research, the dynamic response and energy absorption characteristics of four different types of commercially available glass have been investigated experimentally. Soda Lime, Starphire, Borosilicate, and Fused Silica were characterized using a Dynatup 8250 drop weight impact test system, and a modified Split Hopkinson Pressure Bar (SHPB). In the low-velocity punch-shear experiment, similar trend has been observed for all glass types, and Starphire and Borosilicate demonstrated the highest total energy absorption. High strain-rate SHPB compression tests were carried out on cylindrical glass samples at two different strain-rates. Borosilicate shohigher compressive strength and energy absorption in comparison to the other …

Microstructure, Quasi-Static, And High-Strain Rate Dynamic Characterization Of Metakaolin And Fly Ash Based Geopolymers For Structural Applications, Damian Lee Stoddard

Electronic Theses and Dissertations

Geopolymers are a class of rapid setting cementing systems that have been used as mortar or additives in concrete mixes to improve properties. Several types of geopolymer systems such as metakaolin and fly ash based geopolymers are widely used, and are available in different mixture proportions [1, 2]. Metakaolin (Al2Si2O7), a dehydroxylated form of Kaolinite (Al2Si2O5(OH)4) clay readily available from many sources, provides several benefits whenadded to a concrete mix design or used as a mortar system, including durability, freeze/thaw, acid resistance, and high temperature resistance [3]. Class F fly ash-based mortar geopolymers provide added fire retardation, reduces crack formation, …

Optimization Of Wind Fence Enclosures For Infrasonic Wind Noise Reduction, Johnpaul Russell Abbott

Electronic Theses and Dissertations

A large porous wind barrier enclosure has been built and tested to optimize wind noise reduction at infrasonic frequencies between 0.01-10 Hz in order to develop a technology that is simple, cost effective, and improves upon the limitations of pipe and porous hose arrays. The effects of varying the fence's porosity, modifying its top condition and bottom gap, doubling the height and diameter, and adding a secondary wind barrier were investigated. A simple mathematical model which estimates the wind noise measured at the center of the enclosure was derived based on the measured turbulence and velocity profiles measure outside the …

Finite Element Analysis Of Shear Resistant Mechanisms For Biolaminate Interfaces, Matthew Nelms

Electronic Theses and Dissertations

The Alligator gar possesses a flexible dermal armor consisting of overlapping ganoid scales. Each scale is a bilayer hydroxyapatite and collagen-based bio-laminate for protection against predation. The exoskeleton fish scale is comprised of a stiff outer ganoine layer, a characteristic "sawtooth" pattern at the interface and a compliant bone inner layer with all materials exhibiting a decreasing elastic modulus, yield strength and density through the thickness. Experiments on ganoid scales revealed properties such as damage mitigation and energy dissipation that are unique to biological dermal armor. The objective of this investigation is to develop a fundamental understanding of the stress …

Enhanced Pvdf Film For Multi Energy Harvesting, Ranmunige Nadeeka Karunarathna

Electronic Theses and Dissertations

No abstract provided.

Fiber Reinforcement Compaction In Resin Injection Pultrusion Process, Neerad Shakya

Electronic Theses and Dissertations

Resin injection pultrusion is a cost-effective continuous manufacturing process to produce composites of constant cross-section. In this process, fiber reinforcements are continuously pulled through the injection chamber where liquid resin is injected to cause complete wetout of the fibers before exit. The fiber-resin combination obtained from the injection chamber is then cured to obtain the desired pultruded composite. There are various processing and geometric parameters affecting the wetout process. The main objective of this study is to present a numerical model to simulate the resin flow through the fiber reinforcement when compaction of the fibers is also taken into account. …

Micro-Mechanics Based Representative Volume Element Modeling Of Heterogeneous Cementitious Materials, Mohammadmehdi Shahzamanian Sichani

Electronic Theses and Dissertations

The current work focuses on evaluation of the effective elastic properties of cementitious materials through a voxel based FEA approach. Voxels are generated for a heterogeneous cementitious material (Type-I cement) consisting of typical volume fractions of various constituent phases from digital microstructures. The microstructure is modeled as a micro-scale representative volume element (RVE) in ABAQUS to generate cubes several tens of microns in dimension and subjected to various prescribed deformation modes to generate the effective elastic tensor of the material. The RVE-calculated elastic properties such as moduli and Poisson's ratio are validated through an asymptotic expansion homogenization (AEH) and compared …

Characterizing The Acoustic Properties Of The Jet Lab At The National Center For Physical Acoustics, Joshua Anderson Lieblong

Electronic Theses and Dissertations

Aerodynamic noise has been a problem since the first use of the jet engine for military aircraft in World War II. For further uses of the jet engine to be possible, problems due to jet noise must be researched and addressed. Anechoic chambers were proposed as a testing facility for research in aerodynamic noise because of their supposed free-field characteristics. The international standard ISO 3745-1977 was introduced to determine whether the facilities could be considered anechoic, semi-anechoic, or neither. An experiment was designed to determine at what frequencies the National Center for Physical Acoustics' Jet Lab Facility is non-anechoic, semi-anechoic, …

Smart Nanocoated Structure For Energy Harvesting At Low Frequency Vibration, Sudhanshu Sharma

Electronic Theses and Dissertations

Increasing demands of energy which is cleaner and has an unlimited supply has led development in the field of energy harvesting. Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy that can be stored and used to power other devices. With the recent surge of micro scale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources. In this research, a piezoelectric power generator composite prototype was developed to maximize the power output of the system. A lead zirconate titanate (PZT) composite structure was formed and mounted on a cantilever bar …

A Comparative Study Of Segmented Tungsten Rod Penetration Into A Thick Steel Target Plate, Michael Bryant Presnell

Electronic Theses and Dissertations

This thesis presents results from computational simulations of tungsten alloy segmented rod projectiles (SRP) penetrating an RHA semi-infinite target plate at high velocities. Penetration experimental data show improved penetration efficiency by the segmented projectiles when compared to monolithic (single solid rod) projectiles. For SRP with an aspect ratio (L/D) = 1/8, a loss in penetration efficiency was seen upon successive segment impacts. A numerical simulation impacting tungsten heavy alloy against RHA 4340 steel was performed using the Lagrangian finite element code EPIC 2006. The impact configuration that was modeled consisted of eight successive collinear impacts of discs measured 2mm in …

Effects Of A Heated Turbulent Boundary Layer On Surface Pressure Fluctuations, David William Rich

Electronic Theses and Dissertations

Recent work has shown that spatial correlation of surface pressure fluctuations in a fully turbulent atmospheric boundary layer (ABL) can give information about the velocity field and turbulence. This is of particular importance to the future of wind energy to predict the incoming velocity flow field of wind turbines so as to actively control them for peak operating efficiency and damage reduction. All of the environmental effects on the surface pressure fluctuations need to be fully understood before a suitable flow prediction algorithm can be constructed. One such environmental effect which has not been previously studied is the effect of …

Quantification Of An Ultrasound Test Apparatus And Its Potential Use To Control Nuisance Species In Commercial Aquaculture Settings, Bradley T. Goodwiller

Electronic Theses and Dissertations

As one step in the investigation of using acoustics to improve aquaculture production, work was pursued on the possible use of ultrasound to control the Bolbophorus trematode in commercial catfish ponds. The trematode population can be controlled by eliminating the host ram's horn snail via exposure to high amplitude ultrasound. Initial laboratory tests indicated that a commercially available sonicator (operating at 20 kHz) is capable of killing individual snails in fish tanks. More thorough testing indicated efficiency rates of approximately 35% on batches of 10 snails. In addition to the snails killed immediately, there was evidence that the sonication technique …

Processing Parameters And Chamber Length Impact On Detached Die And Attached Die Resin Injection Pultrusion, Dinesh Raj Palikhel

Electronic Theses and Dissertations

Injection pultrusion is an efficient and highly automated continuous process for high-quality, low-cost, high-volume manufacturing of composites. The main objective of this study is to analyze "attached die configuration" and "detached die configuration" for the better injection pultrusion process. In this work the impact of various processing parameters on complete wet out of composite parts is investigated in the attached die and detached die injection pultrusion with various chamber length considerations. The various processing parameters considered are pull speed, fiber volume fraction, resin viscosity, injection port location and compression ratio. 3-D finite volume technique is used to simulate the liquid …

Development Of An Astm Draft Standard For The Elevated Temperature Moisture Conditioning Of Pultruded Fiber Reinforced Polymer Composites, Tunji Adejumo

Electronic Theses and Dissertations

No abstract provided.