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Articles 1 - 25 of 25
Full-Text Articles in Engineering
Exploration Of Segmented Flow In Microchannels Using The Volume Of Fluid Method In Ansys Fluent, Jace Michael Boudreaux
Exploration Of Segmented Flow In Microchannels Using The Volume Of Fluid Method In Ansys Fluent, Jace Michael Boudreaux
LSU Master's Theses
Segmented flow can be utilized in lab-on-a-chip technologies to speed up chemical and biological analysis. Segmented flow (also known as Taylor flow or the Bretherton problem) has often been explored in circular channels, but rectangular channels are more common for microfluidics applications. To this end, pressure-driven droplet flow in a square microchannel is studied using the volume of fluid method in ANSYS Fluent, a computational fluid dynamics program. It was found that for low Reynolds number (Ret = 0.01) and droplet sizes larger than the channel diameter, the flow is mostly influenced by capillary number and viscosity ratio. The …
Numerical Studies Of Liquid-Liquid Segmented Flows In Square Microchannels Using A Front-Tracking Algorithm, Eamonn Daire Walker
Numerical Studies Of Liquid-Liquid Segmented Flows In Square Microchannels Using A Front-Tracking Algorithm, Eamonn Daire Walker
LSU Doctoral Dissertations
Liquid-liquid segmented flows in a square microchannel are investigated numerically using a hybrid front-tracking/front-capturing method. The code is found to be well-adapted to a large range of flow parameters, but droplet flows are limited by poor accuracy at Laplace number above 100 – 1000 and plug flows are limited by the code’s current inability to adequately model the flow in thin films at low capillary numbers. A Schwarz-Aitken acceleration technique is investigated as a means to reduce computation time, but is found not to be advantageous compared to the parallel multigrid formulation of the code. Numerical simulations are divided into …
On The Thermally Induced Failure Of Rolling Element Bearings, Jafar Takabi
On The Thermally Induced Failure Of Rolling Element Bearings, Jafar Takabi
LSU Doctoral Dissertations
This dissertation is devoted to the investigation of thermally induced seizure of rolling element bearings. A comprehensive thermal model of the rolling element bearings is developed which can predict the operating temperature of the bearing components in a wide range of operating conditions. The validity of this thermal model is verified by comparing the simulation results with a set of experiments. The results of simulations reveal that the rotational speed, oil viscosity and cooling rate of the housing have a significant influence on the operating temperature of the rolling bearings. To provide detailed information about all of the contact forces …
Degradation And Fatigue Involving Dissipated Processes, Md Liakat Ali
Degradation And Fatigue Involving Dissipated Processes, Md Liakat Ali
LSU Doctoral Dissertations
Irreversible material degradation due to cyclic mechanical loading is investigated utilizing the concept of thermodynamic entropy, plastic strain energy, and temperature slope measurement. Uniaxial tension-compression and fully-reversed bending fatigue tests are performed over a wide range of loading conditions with metallic and composite materials subject to both constant- and variable-amplitude loading. A methodology is developed for the estimation of the fatigue fracture entropy (FFE) and fatigue toughness of metallic specimens in a rapid fashion. It is found that the FFE and the fatigue toughness of each material tested are within a small band. The value of FFE is found to …
Healing-On-Demand Polymer Composites Based On Shape Memory Polyurethane Fibers And Polymeric Artificial Muscles, Pengfei Zhang
Healing-On-Demand Polymer Composites Based On Shape Memory Polyurethane Fibers And Polymeric Artificial Muscles, Pengfei Zhang
LSU Doctoral Dissertations
In this dissertation, the healing-on-demand polymer composites based on shape memory polyurethane fibers and artificial muscles are investigated, for understanding and developing a novel healing-on-demand composite so that it would be used for industrial applications that could heal structural-length scale damage and leaking autonomously, repeatedly, efficiently, timely, and molecularly. Firstly, the structural relaxation behavior of shape memory polyurethane (SMPU) fiber was studied by theoretical analysis and experimental test. Then, a self-healing composite based on cold-drawn short SMPU fiber was prepared and tested for evaluating its crack-healing performance. After that, polymer artificial muscle based healing-on-demand composite was developed and characterized. Based …
An Analytic Solution Of The Thermal Boundary Layer At The Leading Edge Of A Heated Semi-Infinite Flat Plate Under Forced Uniform Flow, Robert Jessee
An Analytic Solution Of The Thermal Boundary Layer At The Leading Edge Of A Heated Semi-Infinite Flat Plate Under Forced Uniform Flow, Robert Jessee
LSU Master's Theses
Abstract The heated flat plate under uniform flow has been vastly studied, with the Blasius and Pohlhausen solutions developed over 100 years ago. These solutions are numerical in nature. Here, an analytic solution is found for the temperature and velocity profiles at the leading edge of a heated flat plate under forced uniform flow. By defining a similarity variable the governing equations are reduced to a dimensionless equation with an analytic solution at the leading edge. This report gives justification for the similarity variable via scaling analysis, details the process of converting to similarity form, and presents a similarity solution. …
Heat Transfer Study Of Porous Media With A Temperature Jump Condition, Pravin Kumar
Heat Transfer Study Of Porous Media With A Temperature Jump Condition, Pravin Kumar
LSU Master's Theses
Conjugate heat transfer in a porous media is investigated with a temperature jump condition obtained from kinetic gas theory. The temperature jump appears alongside flow boundary condition when the pressure is low, and considered to be in non-continuum regime. This investigation focuses on both one-dimensional and two-dimensional porous media models. The length scale of the pores is 100 microns. The temperature is ambient, and the pressure is low enough to reach the slip-flow regime. The thermal behavior of porous media is investigated using a slot model with a gas trapped between two solid blocks. Aluminum oxide and air are considered …
Experimental Study Of A Cascade Of Low Pressure Turbine Blades With Upstream Periodic Stator Wakes, Carlos Rene Gonzalez Rodriguez
Experimental Study Of A Cascade Of Low Pressure Turbine Blades With Upstream Periodic Stator Wakes, Carlos Rene Gonzalez Rodriguez
LSU Master's Theses
The objective of this study is to experimentally study film cooling flows. A closed-loop wind tunnel with a four passage linear cascade of US Air Force Research Laboratory (AFRL) ultra-high-lift L1A low pressure turbine (LPT) blades and upstream wake generator is used in conjunction with Particle Image Velocimetry (PIV) flow visualization technique to study turbulent film cooling flows due to the interaction between vanes and blades. Further post-processing in the form of Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) modal analyses is performed to determine the relevant modes that characterize the coherent structures in the flow. An image …
Chemical Structure And Dynamics In Laminar Flame Propagation, Mohsen Ayoobi
Chemical Structure And Dynamics In Laminar Flame Propagation, Mohsen Ayoobi
LSU Doctoral Dissertations
The objective of this dissertation is to investigate fundamental aspects of premixed flame structures as well as flame dynamics that arise due to conjugate heat transfer in narrow channels. Laminar premixed combustion simulations in narrow 2D channels show that conjugate heat transfer allows for combustion of mixtures at small scales that are not flammable at normal conditions. To investigate the impact of conjugate heat transfer, preheated 1D cases with premixed H2/Air fuel are simulated for a wide range of operating conditions based on inlet temperature and equivalence ratio. For post-processing, Chemical Explosive Mode Analysis (CEMA, an eigen-analysis technique) is used …
A Comparative Assessment Of Ergonomic Risk Factors In University Personnel Using Rula And Reba Aiming To Study The Cause And Effect Relationship, Nabila Chowdhury
A Comparative Assessment Of Ergonomic Risk Factors In University Personnel Using Rula And Reba Aiming To Study The Cause And Effect Relationship, Nabila Chowdhury
LSU Master's Theses
The aim of this research was to conduct an ergonomic assessment of working postures and the design of computer workstations of the employees in Louisiana State University. The purpose of the study was threefold- (1) to determine the major ergonomic issues in university employees while working on computer workstations, (2) to compare the two ergonomic assessment tools (RULA and REBA) to see how similarly or differently they assess the risks present in the same working condition and (3) to develop a model that correlates between working condition, work posture and computer workstation design with their effects on musculoskeletal system. This …
Development Of A Three-Dimensional Bioprinter With Inline Light Activation For Bone Tissue Engineering, Colton Alexander Mcelheny
Development Of A Three-Dimensional Bioprinter With Inline Light Activation For Bone Tissue Engineering, Colton Alexander Mcelheny
LSU Master's Theses
Bioprinting offers exciting possibilities for tissue engineering related to tissue and organ failure due to trauma, disease, or aging. This is of substantial societal value as the world populace mean age rises. Current needs for tissue and organ repair far exceed availability. A strategy being explored to counter this imbalance is the single step fabrication of cellular constructs. This paper explores various bioprinting techniques and suggests a custom design for a cost-effective, low-maintenance bioprinting platform for academic research. The platform functionality was validated via two-dimensional image transfer and simple three-dimensional geometries.
On The Role Of Surface Roughness In Elastohydrodynamic Lubrication Of Tribological Components, Mohammad Masjedi
On The Role Of Surface Roughness In Elastohydrodynamic Lubrication Of Tribological Components, Mohammad Masjedi
LSU Doctoral Dissertations
The present dissertation investigates the effect of surface roughness in the elastohydrodynamic lubrication (EHL). Since many essential components of the machinery such as gears, rolling element bearings, cam-followers, and heavily loaded journal bearings operate under the mixed EHL condition, and given the fact that nearly all engineering surfaces are rough to some extent, there is a need for an extensive research which can realistically quantify the effect of the surface roughness in such applications. We thus seek to develop an applied engineering approach for the treatment of the mixed EHL for prediction of the performance of machinery. Both line-contact and …
Physics And Applications Of A Pdms Based Centrifugal Microfluidic System, Ziliang Cai
Physics And Applications Of A Pdms Based Centrifugal Microfluidic System, Ziliang Cai
LSU Doctoral Dissertations
The objective of this research work is to develop a centrifugal microfluidic system for general purposes based on microfabrication technologies including SU-8 photolithography, polydimethylsiloxane (PDMS) casting. The main contribution of this research is to integrate a flyball governor system into the polymer based centrifugal microfluidic platform. A series of function units are developed based on this unique mechanism. In the first part, three pinch valve systems were designed and tested. The first one is based on the magnetic force and the second one is on the basis of spring force and the last one is a membrane valve. All valving …
On An Effective Submodeling Procedure For Stresses Determined With Finite Element Analysis, Ajay Ashok Kardak
On An Effective Submodeling Procedure For Stresses Determined With Finite Element Analysis, Ajay Ashok Kardak
LSU Doctoral Dissertations
Submodeling can enable stress analysts using finite elements to focus analysis on a subregion containing the stress concentration of interest, with consequent computational savings. Such benefits are only truly realized if the boundary conditions on the edges of the subregion that were originally contained within the global region are sufficiently accurate. These boundary conditions are drawn from initial global finite element analysis (FEA), and consequently themselves have errors that in turn lead to errors in the stresses sought. When these last boundary-condition errors are controlled, and the discretization errors incurred by the FEA of ensuing submodels are also controlled, submodeling …
Study Of Active Vibration Control Using The Method Of Receptances, Amit Maha
Study Of Active Vibration Control Using The Method Of Receptances, Amit Maha
LSU Doctoral Dissertations
Using the Method of Receptance, it is possible in general to assign 2_x0002_ poles (i.e. n conjugate pairs) of an axially vibrating rod of variable cross section by sensing the state at _x0002_ points along the rod. Using the sensor data, closed loop feedback control gains can be calculated by solving a simple set of linear equations. The feedback gains can be applied to generate the required control force using an actuator. This partial pole assignment can be done without continuous or discrete analytical modeling. Therefore, the physical parameters such as the rigidity, the density, and the variable cross-sectional area …
Challenges Towards Structural Integrity And Performance Improvement Of Welded Structures, Mohammad Washim Dewan
Challenges Towards Structural Integrity And Performance Improvement Of Welded Structures, Mohammad Washim Dewan
LSU Doctoral Dissertations
Welding is a fabrication process that joint materials, is extensively utilized in almost every field of metal constructions. Heterogeneity in mechanical properties, metallurgical and geometrical defects, post-weld residual stresses and distortion due to non-linear welding processes are prime concerns for performance reduction and failures of welded structures. Consequently, structural integrity analysis and performance improvement of weld joints are important issues that must be considered for structural safety and durability under loading. In this study, an extensive experimental program and analysis were undertaken on the challenges towards structural integrity analysis and performance improvement of different welded joints. Two widely used welding …
Molecular Dynamics Simulation Study Of Single Dna Nucleotides Transport Through Nanoslits, Kai Xia
Molecular Dynamics Simulation Study Of Single Dna Nucleotides Transport Through Nanoslits, Kai Xia
LSU Doctoral Dissertations
There is potential for flight time based DNA sequencing involving disassembly into individual nucleotides which would pass through a nanochannel with 2 or more detectors. Molecular dynamics simulation of electrophoretic motion of single DNA nucleotides through 3 nm wide hydrophobic slits was performed. Electric field strength (E) varied from 0.0 to 0.6 V/nm. Slit walls were smooth or had a roughness similar to nucleotide size. Multiple nucleotide-wall adsorptions occurred. The electric field did not influence the nucleotide adsorption and desorption mechanism for E ¡Ü 0.1 V/nm, but influenced nucleotide orientation relative to the field direction. The nucleotide-wall interactions differed due …
Deposition And Characterization Of Ceramic Thin Films And A New Experimental Approach To Evaluate The Mechanical Integrity Of Film/Substrate Interfacial Layers, Yang Mu
LSU Doctoral Dissertations
Due to their corrosion resistance, high temperature stability, high strength, and high hardness, refractory ceramic thin films and coatings have been utilized for surface engineering of mechanical components and mechanical fabrication tools. Adhesion between ceramic thin films and coatings and the substrate is of critical concern for performance and life time of coated systems. In this dissertation, a custom designed and constructed ultra-high-vacuum (UHV) vapor phase deposition system was used for the preparation of ceramic thin films through low-pressure high-density plasma assisted physical vapor deposition (PVD) methods. Deposited thin films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), …
Effect Of Appointment Schedules On The Operational Performance Of A University Medical Clinic, Arunn Pisharody Vijayan
Effect Of Appointment Schedules On The Operational Performance Of A University Medical Clinic, Arunn Pisharody Vijayan
LSU Master's Theses
Healthcare costs in the United States are one of the highest in the world. The healthcare expenditure alone accounted for 17.9% of the Gross Domestic Product of US in 2011. The National Healthcare Expenditure (NHE) is expected to increase at an annual rate of 6.6% from $ 2.6 Trillion in 2010 to $ 4.5 Trillion in 2019. The per capita expenditure for hospital outpatients and physicians has been the highest among other hospital expenses. This escalation in expenses created a need for productivity improvements in the healthcare industry to control costs. Some of the common problems encountered in outpatient clinics …
Modeling Two-Phase Flow And Heat Transfer In Polygonal Microchannels, Sai Sashankh Rao
Modeling Two-Phase Flow And Heat Transfer In Polygonal Microchannels, Sai Sashankh Rao
LSU Doctoral Dissertations
Microfluidics is a burgeoning research area with applications ranging from microfluidic cooling to biomolecule synthesis. Here we study two problems to gain an improved understanding of two-phase flow and heat transfer in microfluidic devices. We also study a third problem on boundary layer flow out of theoretical interest. In the first problem, we study the heat and mass transfer in polygonal micro heat pipes under small imposed temperature differences. A micro heat pipe, used in electronics cooling, consists of a closed polygonal microchannel filled with a wetting liquid and a long vapor bubble. We model the evaporation, fluid flow, and …
Heat Transfer And Film Cooling On A Gas Turbine Blade And Shroud, Onieluan Tamunobere
Heat Transfer And Film Cooling On A Gas Turbine Blade And Shroud, Onieluan Tamunobere
LSU Doctoral Dissertations
At a fixed pressure ratio, the thermodynamic efficiency and net power output of a gas turbine engine increases with an increase in the turbine inlet temperature. Cooling is necessary because of the thermal limits of the engine materials. This research studies through experimentation, the heat transfer and cooling of critical gas turbine components including the shroud and blade tip. In the first phase, the shroud heat transfer behavior and the effectiveness of shroud cooling under the conditions of rotation is undertaken in a single stage turbine at a design rotation speed of 550 rpm, at off-design speeds and for varying …
The Effects Of Work Zone Configurations On Physiological And Subjective Workload, Mahmoud Shakouri Hassanabadi
The Effects Of Work Zone Configurations On Physiological And Subjective Workload, Mahmoud Shakouri Hassanabadi
LSU Master's Theses
There is a dearth of research on the effect of driving through work zones on physiological and subjective workload of drivers. The objectives of this research were to (a) study the effect of work zones and traffic density on physiological measures of workload, subjective workload and performance variables (b) study the relationship between physiological measures of workload, subjective workload and performance variables. Conventional lane merge (CLM), joint lane merge (JLM) and a road without a work zone (control) were modeled with high and low traffic density by using a full-size driving simulator. 13 female and 17 male students volunteered to …
Radiation Heat Transfer In A Particulate Medium Using A Ray Tracing Method, Manish B. Patil
Radiation Heat Transfer In A Particulate Medium Using A Ray Tracing Method, Manish B. Patil
LSU Master's Theses
In the present work, a complete 3D simulation of ray tracing model is developed for studying the radiation heat transfer, associated with laser based additive manufacturing, in both thick and thin particulate beds by using the Monte Carlo method. Additional program is developed for creating different types of packing structures such as simple cubic, rhombohydral and random packing. The scattering mechanisms in the particulate beds for large opaque spheres are evaluated using the specular and diffuse reflection methods. Further, a novel approach has been added to the model to include isotropic, forward and backward scattering mechanisms for a medium which …
Fabrication And Characterization Of Miniaturized Components Based On Extruded Ceramic-Filled Polymer Blends, Khurshida Sharmin
Fabrication And Characterization Of Miniaturized Components Based On Extruded Ceramic-Filled Polymer Blends, Khurshida Sharmin
LSU Doctoral Dissertations
The objective of this work is to develop an improved manufacturing process for microstructured ceramic components that is based on co-extrusion. Co-extrusion of structured feedrods holds promise for development of multi-layered, functionally graded and/or textured structures. However, it requires a polymer binder that is difficult to remove before structures can be sintered to full density. A two-step debinding is introduced to eliminate debinding defects that are commonly observed in thermal debinding (TD). Cracking is a major issue due to a lack of pore spaces for outgassing of pyrolysis products in traditional TD. In two-step debinding, a soluble binder is removed …
Multiscale Modeling Of Smart Materials Under Static And Dynamic Thermo-Mechanical Loading, Soodabeh Sharafi
Multiscale Modeling Of Smart Materials Under Static And Dynamic Thermo-Mechanical Loading, Soodabeh Sharafi
LSU Master's Theses
Engineering material systems with tailored capabilities are a topic trend in plethora of research. Polymer based Artificial Muscle, PAM, and Shape memory polymer fiber, SMPF, enable structural engineers to incorporate smartness functionality into their design through programming cycles. Smartness functionality leads to the production of artificial muscles with different load carrying capability. SMPF is another category of smart materials, which are capable of being micro-structurally engineered to isolate vibration at different temperature and frequency conditions. The smartness functionality offers the adjustment between inherent properties of these materials with their industrial applications through modeling techniques. Mixture of phenomenological, numerical, mathematical models …