Mechanical Engineering Commons^™

Investigation Of Vorticity Confinement As A High Reynolds Number Turbulence Model, Nicholas F. Lynn

Doctoral Dissertations

Vorticity Confinement (VC) is a computational technique used to compute fluid flows with thin vortical regions in an accurate and efficient manner. Recent results have shown that it accurately computes the turbulent wake behind blunt bodies at large Reynolds numbers. Physically, these flows are dominated by thin vortices that convect downstream with the flow, which accounts for the important higher-order velocity statistics. These thin vortices are artificially dissipated with traditional methods, whereas VC can accurately compute them.

VC consists of a set of discrete equations with the confinement appearing as a source term in the discretized momentum equations. The term …

Novel Numerical Approaches For The Resolution Of Direct And Inverse Heat Transfer Problems, Gregory Evan Osborne

Doctoral Dissertations

This dissertation describes an innovative and robust global time approach which has been developed for the resolution of direct and inverse problems, specifically in the disciplines of radiation and conduction heat transfer.

Direct problems are generally well-posed and readily lend themselves to standard and well-defined mathematical solution techniques. Inverse problems differ in the fact that they tend to be ill-posed in the sense of Hadamard, i.e., small perturbations in the input data can produce large variations and instabilities in the output. The stability problem is exacerbated by the use of discrete experimental data which may be subject to substantial measurement …

Estimation Of Surface Temperature And Heat Flux Using Embedded Thermocouples, Jeffrey Daniel King

Masters Theses

This thesis investigates several new methods for estimating surface temperature and heat flux based on thermocouples embedded within the interior of a test article. The test apparatus was a Mach 2 axisymmetric rocket nozzle with probes embedded at depths of 1/8” and 1/4” from the inner surface of the nozzle at the throat and exit locations. Three methods for numerically estimating temperature and heat flux at the surface of the nozzle were considered: a one-thermocouple slab-coordinate method, a two-thermocouple slabcoordinate method, and a finite-element analysis (FEA) based on a one-dimensional cylindrical coordinate method. Comparisons between the methods, as well as …

Virtual Modeling And Verification Of Air-Ride Truck Seat Using Multibody Dynamics For Whole Body Vibration Evaluation, Devdutt Nandkishore Shende

Masters Theses

To aid the tuning and optimization of the truck seat design to specific trucks and road profiles during the design phase, this study presents the development and validation of a virtual seat model. This study also assess the utility of the model for whole body vibrations evaluation.

The virtual dynamic seat model was developed in MSC. ADAMS/VIEW. The critical elements like the suspension mechanism, the airspring, dampers and seat cushion were modeled using tested data. To validate the performance of the virtual model, prototype tests were performed using the MTS 6-axis simulator. The modeling process was targeted to achieve a …

Inverse Kinematics Based On Fuzzy Logic And Neural Networks For The Wam-Titan Ii Teleoperation System, Joong-Kyoo Park

Masters Theses

The inverse kinematic problem is crucial for robotics. In this paper, a solution algorithm is presented using artificial intelligence to improve the pseudo-inverse Jacobian calculation for the 7-DOF Whole Arm Manipulator (WAM) and 6-DOF Titan II teleoperation system. An investigation of the inverse kinematics based on fuzzy logic and artificial neural networks for the teleoperation system was undertaken. Various methods such as Adaptive Neural-Fuzzy Inference System (ANFIS), Genetic Algorithms (GA), Multilayer Perceptrons (MLP) Feedforward Networks, Radial Basis Function Networks (RBF) and Generalized Regression Neural Networks (GRNN) were tested and simulated using MATLAB. Each method for identification of the pseudo-inverse problem …

Analysis Of Electrical Activity Of The Core Muscles Exposed To Whole-Body Vibrations While Driving A Tractor Trailer Using Electromyography Device, Harini Mangavelli

Masters Theses

Lower back disorders are observed to be the most significant problem for most of the industrial workers who operate commercial vehicles. A person sitting can have 40% higher load on the lumbar spine than when standing. Human core muscles related to spinal movement respond to rapid potential motions related to external acceleration inputs of vibration in order to control body posture, the increased muscle tension can result in muscle fatigue. The over use of muscles, vibration exposure combined with dehydration of spine and long term seating can lead to lower back pain and axial discomfort to the drivers. Electromyography (EMG) …

Development Of An Integrated Opto-Electric Biosensor To Dynamically Examine Cytometric Proliferation And Cytotoxicity, Chang Kyoung Choi

Doctoral Dissertations

My doctoral research has focused on the development of microscale optical techniques for examining micro/bio fluidics. Preliminary work measured the velocity field in a microchannel, by optical slicing, using Confocal Laser Scanning Microscopy (CLSM). Next, Optical Serial Sectioning Microscopy (OSSM) was applied to examine thermometry by detecting the free Brownian motion of nano-particles suspended in mediums at different temperatures. An extension of this work used objective-based Total Internal Reflection Fluorescence Microscopy (TIRFM) to examine the hindered Brownian motion of nano-particles that were very close to a solid surface (within 1 mm).

An optically transparent and electrically conductive Indium Tin Oxide …

Intrustive Probe Measurements In A High-Temperature Mach Two Flow, Sonya Renee Nelson

Masters Theses

To acquire heat transfer measurements of a high temperature Mach two flow a water-cooled calorimeter was placed in the flow and the water temperature rise was used to calculate the heat transfer rate and the recovery temperature of the gas. In addition, a graphite rod with a stainless steel tube at its core was used to measure the total pressure of the flow. This pressure probe was swept through the flow for two test runs to acquire a stagnation pressure profile of the gas flow. All results were compared to NASA CEA computer simulation code results. The heat transfer and …

Influence Of The Sampling Procedure On Extracted Jet Engine Exhaust Gas Emission Samples, Ashley Dawn Owens

Masters Theses

The purpose of this thesis is to analyze the effects of an intrusive sample extraction process on the thermo-chemistry of extracted gas samples taken from exhaust of a GE-J85-H turbojet engine. The engine testing took place at University of Tennessee Space Institute in Tullahoma, TN, where the J85 was installed in a test bay of a research facility. The results of the analysis validate that testing methods used had a low probability of disturbing the exhaust chemistry. The tools used to analyze the thermal history of the extracted samples were the NASA CEA and LSENS programs. Several different cases of …

Effect Of Length On The Performance Of Lean NoX Traps, Vitaly Y. Prikhodko

Masters Theses

The effect of monolith length on the NO_x performance of two different Lean NO_x Traps has been investigated using a bench flow reactor (BFR). The washcoat composition of one of the catalysts consists of Pt/K/γ-Al₂O₃; the major components of the other catalyst include Pt, Pd, Rh, barium, ceria and zirconia supported on γ-alumina washcoat. Samples of 2.22-cm in diameter and length of 2.54, 5.08 and 7.62-cm within each LNT were evaluated with long and short-cycle experiments at a fixed gas hourly space velocity, and results were compared between samples of different lengths. No significant …

Analysis And Optimization Of Partial Length, Constrained Damping Layers, Shing-Jia Tang

Doctoral Dissertations

A laminated beam with constrained damping layers is analyzed. The normal strain in the longitudinal direction and shear strain in the viscoelastic layer is considered. Hamilton’s principle is used to derive equations of motion and boundary conditions. A 6th order equation is used to describe the portion of the beam covered with a constrained damping layer and a 4th order equation is used to describe the remainder of the beam. The characteristic equations are solved numerically with a gradient-based optimization method in order to determine normalized loss factor values. The loss parameter (normalized loss factor) is shown to be a …

Modeling Coordinate Measuring Machine Scanning Operations, Pamela Murray Moor

Doctoral Dissertations

International standards require that dimensional inspection operations include an assessment of measurement uncertainty. Scanning coordinate measuring machines (CMMs) are frequently used to measure part surfaces and features, and there is a continuing need to improve their performance for high precision measurement applications. This research provides a mechanism for minimizing the uncertainty of measurements made with a CMM in scanning mode by developing a model of CMM scanning that allows selection of optimum scanning parameters.

The method for selecting scanning parameters is based on models developed from measurements of a ring with a constant five micrometer amplitude swept sine wave machined …

Mathematical Modeling Of Reverse Flow Oxidation Catalysts, Barath Raghavan

Masters Theses

A theoretical model and a computer simulation on methane (CH4) reduction in a simulated natural gas exhaust mixture are performed for a Reverse-Flow Oxidation Catalyst. This theoretical model is to predict the conversion of methane flowing through an oxidation catalyst with periodic reversal of flow direction. The model developed for this purpose is a transient, 1-Dimensional plug flow model with gas phase reactions and surface reactions. The derivation of the model resulted in the mole balance equation and the energy balance equation for the gas phase and the solid phase. The momentum equation for this model is neglected as it …

Energy Harvesting From Vibration Of A Bridge, Sri Harish Valluru

Masters Theses

Basic research in smart materials and structural systems has demonstrated great potential for enhancing the functionality, serviceability and durability of civil and mechanical infrastructure systems. These smart materials (like piezoelectric materials) can be used as mechanisms to transfer mechanical energy, usually ambient vibration, into electrical energy that can be stored and used to power other devices. The intelligent renewal of aging and deteriorating civil and mechanical infrastructure systems includes efficient and innovative use of high performance sensors, actuators, and structural systems. In this work, a computational model is developed to generate power from the ambient vibration of a single span …

Energy Harvesting Using Optimized Piezoelectric Microcantilevers, Ahmed Mohamed Elalfy

Masters Theses

In this thesis, the energy producing capabilities and efficiency of Piezoelectric materials for ambient energy harvesting from multi-layered micro-cantilevers are analyzed. The cantilevers are then optimized utilizing a homogenization approach involving the redistribution of materials in all regions throughout the three dimensional model to yield the greatest voltage output for a specified tip force under static loading; This would be analogous to having the greatest energy production. The design of the model using the Finite Element Analysis (FEA) software ABAQUS is used in conjunction with a commercial FORTRAN optimization code, where the FEA software handles the mechanical design aspect of …