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Articles 1 - 24 of 24
Full-Text Articles in Engineering
Direct Numerical Simulation Of Cylindrical Particle-Laden Gravity Currents, Nadim Zgheib, Thomas Bonometti, S. Balachandar
Direct Numerical Simulation Of Cylindrical Particle-Laden Gravity Currents, Nadim Zgheib, Thomas Bonometti, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We present results from direct numerical simulations (DNS) of cylindrical particle-laden gravity currents. We consider the case of a full depth release with monodisperse particles at a dilute concentration where particle–particle interactions may be neglected. The disperse phase is treated as a continuum and a two-fluid formulation is adopted. We present results from two simulations at Reynolds numbers of 3450 and 10,000. Our results are in good agreement with previously reported experiments and theoretical models. At early times in the simulations, we observe a set of rolled up vortices that advance at varying speeds. These Kelvin–Helmholtz (K–H) vortex tubes are …
Pressure Field Estimation Using Particle Image Velocimetry, Jean O. Calzada
Pressure Field Estimation Using Particle Image Velocimetry, Jean O. Calzada
Theses and Dissertations
In recent years, scientist and engineers have shown the advantages created by using the Particle Image Velocimetry (PIV) method as flow diagnostic tool to characterize instantaneous velocity fields. One of the important benefits is found on its non-intrusive nature, this leads to accurate velocity fields. From the velocity field obtained by PIV important quantities can be derived, such as pressure and vorticity. The present study, uses PIV data of an incompressible turbulent pulsed jet to determine the pressure field associated with the flow field. The pressure is calculated by using the averaged velocity field along with three different fundamental equation: …
Modeling The Residual Useful Life Of Railroad Bearing Grease, Thania Alejandra Martinez
Modeling The Residual Useful Life Of Railroad Bearing Grease, Thania Alejandra Martinez
Theses and Dissertations
Railroad bearing performance is often constrained by the life of its lubricant. The lubricant life is determined by tribomechanical processes that are present during bearing operation. No known physical models exist to predict the railroad bearing lubricant life. This thesis summarizes the efforts undertaken in the development of empirical models that can accurately predict the residual useful life of railroad bearing grease. Modeling techniques to be employed include regression, regression trees, and split plots. The grease samples used to populate this model come from healthy and faulty bearings that were run under different loads, speeds, and ambient conditions in a …
Dynamics Of Non-Circular Finite-Release Gravity Currents, Nadim Zgheib, T. Bonometti, S. Balachandar
Dynamics Of Non-Circular Finite-Release Gravity Currents, Nadim Zgheib, T. Bonometti, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
The present work reports some new aspects of non-axisymmetric gravity currents obtained from laboratory experiments, fully resolved simulations and box models. Following the earlier work of Zgheib et al. (Theor. Comput. Fluid Dyn., vol. 28, 2014, pp. 521–529) which demonstrated that gravity currents initiating from non-axisymmetric cross-sectional geometries do not become axisymmetric, nor do they retain their initial shape during the slumping and inertial phases of spreading, we show that such non-axisymmetric currents eventually reach a self-similar regime during which (i) the local front propagation scales as t1/2 as in circular releases and (ii) the non-axisymmetric front has a self-similar …
Propagation And Deposition Of Non-Circular Finite Release Particle-Laden Currents, Nadim Zgheib, Thomas Bonometti, S. Balachandar
Propagation And Deposition Of Non-Circular Finite Release Particle-Laden Currents, Nadim Zgheib, Thomas Bonometti, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
The dynamics of non-axisymmetric turbidity currents is considered here for a range of Reynolds numbers of O (104) when based on the initial height of the release. The study comprises a series of experiments and highly resolved simulations for which a finite volume of particle-laden solution is released into fresh water. A mixture of water and polystyrene particles of mean diameter 𝑑̃𝑝=300𝜇m and mixture density 𝜌̃𝑐=1012kg/m3 is initially confined in a hollow cylinder at the centre of a large tank filled with fresh water. Cylinders with two different cross-sectional shapes, but equal cross-sectional areas, are examined: a circle and a …
Fabrication Of Cellulose Fine Fiber Based Membranes Embedded With Silver Nanoparticles Via Forcespinning, Fenghua Xu, Baicheng Weng, Luis A. Materon, Anxiu Kuang, Jorge A. Trujillo, Karen Lozano
Fabrication Of Cellulose Fine Fiber Based Membranes Embedded With Silver Nanoparticles Via Forcespinning, Fenghua Xu, Baicheng Weng, Luis A. Materon, Anxiu Kuang, Jorge A. Trujillo, Karen Lozano
Mechanical Engineering Faculty Publications and Presentations
This study presents the successful development of cellulose fiber based membranes embedded with silver nanoparticles. These fine fiber membranes were developed utilizing the Forcespinning (FS) technique followed by alkaline hydrolysis treatment. The fiber morphology, homogeneity and yield were optimized by varying spinning parameters such as polymer concentration and angular velocity of the spinnerets. The structure, thermal and mechanical properties, and water absorption capability of the developed membranes were investigated. The cellulose acetate (CA) present in the membrane was converted to cellulose in the presence of embedded silver nanoparticles by alkaline hydrolysis. The silver nanoparticles embedded cellulose membrane exhibits outstanding water …
Wind Tunnel Flow Characterization Utilizing Turbulence Spheres, David Omar Cano
Wind Tunnel Flow Characterization Utilizing Turbulence Spheres, David Omar Cano
Theses and Dissertations - UTB/UTPA
When it comes to designing products that will be highly subjected to the aerodynamics of the atmospheric freestream, it’s vital to take into consideration parameters such as geometry and surface smoothness. The optimization of the performance of certain products may be done so with the usage of wind tunnel testing. In order to utilize this tool to its full potential, the flow quality must be pre-determined before running tests. In determining the flow quality there are two main parameters needed to obtain this value. These parameters are referred to as the Turbulence Factor (TF) and Turbulence Intensity (TI). To calculate …
Onboard Load Sensor Prototype For Use In Freight Railcar Service, Thomas Michael Diedrich
Onboard Load Sensor Prototype For Use In Freight Railcar Service, Thomas Michael Diedrich
Theses and Dissertations - UTB/UTPA
Determining the exact load carried by an individual railcar is crucial in the railroad industry. With an accurate load measurement, the filling process can be optimized to provide maximum cargo load without exceeding the loading thresholds set by the Association of American Railroads (AAR). In addition to optimizing the cargo load, an accurate load measurement will make it possible to identify any load imbalance in the railcar which has detrimental effects on bearing. Previous work conducted with a strain-gauge-based load sensor suspended between a thermoplastic steering pad and a bearing adapter provided accurate load data in the laboratory setting. This …
Natural Polymer Based Composite Scaffolds For Tissue Engineering Applications, Marcos R. Villarreal
Natural Polymer Based Composite Scaffolds For Tissue Engineering Applications, Marcos R. Villarreal
Theses and Dissertations - UTB/UTPA
The fabrication, characterization, and bio-assessment of two types of perspective tissue engineering (TE) scaffolds are presented. Principally derived of biopolymers, both types of scaffolds generally followed porous scaffold methodologies for synthesis. Differentiating the two scaffold varieties was chiefly driven by crosslinking attainment, where crosslinking is argued to add structural stability and aid in regulating biodegradability rates in TE scaffolds. Microwave irradiation via conventional microwave was one method used to prospectively crosslink cornstarch to chitosan and sodium alginate. Triethyl orthoformate, was used to prospectively crosslink collagen and chitosan. After the scaffolds were “crosslinked” they were subjected to freeze drying techniques in …
Investigation Of Slective Laser Melting Of Mecanically Alloyed Metastable Al5fe2 Powder, Hugo Montiel
Investigation Of Slective Laser Melting Of Mecanically Alloyed Metastable Al5fe2 Powder, Hugo Montiel
Theses and Dissertations - UTB/UTPA
Selective Laser Melting (SLM), an Additive Manufacturing (AM) technology, enables the production of complex structured metal products. Aluminum alloys are used in SLM as high-strength lightweight materials for weight reduction in structural components. Previous investigations report high laser powers (300 W) and slow scanning speeds (500 mm/s) to process aluminum alloys under SLM. This research investigates the SLM processing of Al-Fe alloy by utilizing metastable Al5Fe2 powder system produced by mechanical alloying. Metastable systems are thermodynamically activated with internal energy that can generate an energy shortcut when processing under SLM. The optimum laser power, scan speeds and scan distances were …
Two-Dimensional Dynamics Model Of The Lower Limb To Include Viscoelastic Knee Ligaments, Eduardo Granados
Two-Dimensional Dynamics Model Of The Lower Limb To Include Viscoelastic Knee Ligaments, Eduardo Granados
Theses and Dissertations - UTB/UTPA
A dynamic, 2D, anatomical knee joint model has been developed to simulate knee reactions to external input forces. A deformable contact area approach is used to find contact forces and moments, and a method of applying nonlinear viscoelastic ligament strain rate response was also developed and implemented on the model to account for the effects of viscoelasticity on the ligament fibers. The ligaments were then tested for various deficiencies to identify their effects on the natural frequency of the knee. Internal knee forces from ligaments, muscles, and contacting surfaces are modeled and then numerically found for different exercises. Static and …
Two Dimensional Inverse Dynamics Model Of Human Knee Dynamics During The Moderate Squat Exercise, Ricardo Gomez Jr.
Two Dimensional Inverse Dynamics Model Of Human Knee Dynamics During The Moderate Squat Exercise, Ricardo Gomez Jr.
Theses and Dissertations - UTB/UTPA
The purpose of this research is to investigate the internal forces on the human knee joint during moderate squat exercise. An inverse dynamics, two dimensional, anatomic dynamic knee model is developed. The model describes the motion in the sagittal plane of human leg, and includes tibia, femur, ligamentous knee structures, tendons and muscles. The software package Matlab is used to solve the inverse dynamics model. Numerical simulations are conducted for walking (the stance phase of the gait cycle) in order to validate the model, and for moderate squatting in order to predict ligament, contact and muscle forces during this exercise.
Development, Optimization, And Implementation Of A Vibration Based Defect Detection Algorithm For Railroad Bearings, Amy Gonzalez
Development, Optimization, And Implementation Of A Vibration Based Defect Detection Algorithm For Railroad Bearings, Amy Gonzalez
Theses and Dissertations - UTB/UTPA
Of the three main rail accident types in the United States, derailments are the most common. Studies have shown that derailments occurring above 25 mph are caused by equipment failures such as bearing failures. As a preventative measure, condition-monitoring systems are required to detect defective bearings in the field. Based on data compiled from multiple experiments of healthy and defective bearings at UTPA, an algorithm has been devised to identify bearing abnormalities. Vibration analysis techniques are utilized to potentially determine whether a bearing is defective and the defect type and size using the acquired vibration signatures. Implementation of a defect …
Nonlinear Dynamics Of Electrostatically Actuated M/Nems Plates To Include Casimir And Van Der Waals Effects, Reynaldo Oyervides
Nonlinear Dynamics Of Electrostatically Actuated M/Nems Plates To Include Casimir And Van Der Waals Effects, Reynaldo Oyervides
Theses and Dissertations - UTB/UTPA
The amplitude-frequency response and voltage-amplitude response of electrostatically actuated micro and nano-electromechanical systems (M/NEMS) clamped circular plates are investigated. The system is actuated by soft AC voltage at frequency near half natural frequency of the plate, and another case near natural frequency of the plate, they resulting in primary and parametric resonances of the system, respectively. The system is first analytically modeled using the Method of Multiple Scales (MMS). MMS results are then compared to Reduced Order Model (ROM) method frequency response numerical simulations. Besides MMS and ROM, time response simulations are conducted. The agreement of the frequency responses of …
Development Of Metallic And Ceramic Nanotubes Via Magnetron Sputtering, Hillario Cortez
Development Of Metallic And Ceramic Nanotubes Via Magnetron Sputtering, Hillario Cortez
Theses and Dissertations - UTB/UTPA
Nanotechnology has been extensively studied throughout the years and has allowed for the development of new structures and technologies. Nanofibers in particular have intrinsically unique properties such as large surface area to volume ratio. Nanofiber structures have a wide range of applications that include: catalysts, sensors, biomedical scaffolds, filtration devices, high performance textiles, energy storage systems, sensitized solar cells, photonics, nanocomposites, membranes, drug delivery systems, and electronics. The objective of this work is to fabricate nanotubular structures by employing the template approach. The template approach consists in the fabrication of circular shaped templates, nanofibers, and then coating the template fibers …
A Study Of The Selective Laser Alloying Of Elemental Titanium And Boron Powder, Yingbin Hu
A Study Of The Selective Laser Alloying Of Elemental Titanium And Boron Powder, Yingbin Hu
Theses and Dissertations - UTB/UTPA
To better understand the selective laser alloying process of elemental titanium and boron powder, theoretic models are created which takes material related, reaction related, laser related, and other affecting factors into consideration. These models do help interpret the corresponding experiment results. In turn, the related experiment results validate the theoretic models created. In practice, the experiments with two different molar ratios of 1:2 and 4:1 between titanium and boron are carried out. The huge amount of energy released because of reaction between titanium and boron during laser irradiation makes it hard to understand and control the alloying process. At the …
Computational Prediction Of Remodeling Of Collagen Fiber Network In Articular Cartilage Under Dynamic Unconfined Compression, Juan Andres Coello Amado
Computational Prediction Of Remodeling Of Collagen Fiber Network In Articular Cartilage Under Dynamic Unconfined Compression, Juan Andres Coello Amado
Theses and Dissertations - UTB/UTPA
A poroelastic finite element model of a heterogeneous cartilage disk was created based on previous studies and experimental setups; this allows us to study cartilage behavior under dynamic unconfined compression. Previous studies have used a Post Hoc approach, which consist of searching for patterns or relationships between predicted mechanical parameters obtained through computational and experimental results. Our goal in this study is to take the same Post-Hoc approach and identify patterns between predicted mechanical parameters, such as fiber strain or stress, and experimentally-measured collagen fiber distribution (i.e. reorientation of fibers under dynamic unconfined compression). After computational predictions were obtained, it …
Tracking Of Spall Deterioration On Tapered Roller Bearings, Amy Gonzalez, Constantine Tarawneh, Ping Hu, Joseph A. Turner, Brent Wilson
Tracking Of Spall Deterioration On Tapered Roller Bearings, Amy Gonzalez, Constantine Tarawneh, Ping Hu, Joseph A. Turner, Brent Wilson
Mechanical Engineering Faculty Publications and Presentations
Fatigue spall initiation is one of the major modes of premature bearing failure. The spall initiation is often exacerbated by the presence of impurities in the near-surface region (∼400 μm) of the bearing raceways. Once a spall initiates, it can propagate rapidly, leading to abnormal bearing operation and possible catastrophic failure if not detected early. Testing performed at the University of Texas-Pan American (UTPA) has focused on ultrasonically scanned tapered roller bearings found to have inclusion content within 400 μm of the surface of the raceways. These bearings undergo accelerated service life tests in which spall initiation is detected and …
Fatigue Life Estimation Of Modified Railroad Bearing Adapters For Onboard Monitoring Applications, Alexis Trevino, Arturo A. Fuentes, Constantine Tarawneh, Joseph Montalvo
Fatigue Life Estimation Of Modified Railroad Bearing Adapters For Onboard Monitoring Applications, Alexis Trevino, Arturo A. Fuentes, Constantine Tarawneh, Joseph Montalvo
Mechanical Engineering Faculty Publications and Presentations
This paper presents a study of the fatigue life (i.e. number of stress cycles before failure) of Class K cast iron conventional and modified railroad bearing adapters for onboard monitoring applications under different operational conditions based on experimentally validated Finite Element Analysis (FEA) stress results. Currently, freight railcars rely heavily on wayside hot-box detectors (HBDs) at strategic intervals to record bearing cup temperatures as the train passes at specified velocities. Hence, most temperature measurements are limited to certain physical railroad locations. This limitation gave way for an optimized sensor that could potentially deliver significant insight on continuous bearing temperature conditions. …
Nanofiber-Based Membrane Separators For Lithium-Ion Batteries, Mataz Alcoutlabi, Hun Lee, Xiangwu Zhang
Nanofiber-Based Membrane Separators For Lithium-Ion Batteries, Mataz Alcoutlabi, Hun Lee, Xiangwu Zhang
Mechanical Engineering Faculty Publications and Presentations
Nanofiber-based membranes were prepared by two different methods for use as separators for Lithium-ion batteries (LIBs). In the first method, Electrospinning was used for the fabrication of Polyvinylidene fluoride PVDF nanofiber coatings on polyolefin microporous membrane separators to improve their electrolyte uptake and electrochemical performance. The nanofiber-coated membrane separators show better electrolyte uptake and ionic conductivity than that for the uncoated membranes. In the second method, Forcespinning® (FS) was used to fabricate fibrous cellulose membranes as separators for LIBs. The cellulose fibrous membranes were made by the Forcespinning® of a cellulose acetate solution precursor followed by a subsequent alkaline hydrolysis …
Surface Characterization Of 316l Stainless Steel For Biomedical Applications, Lawrence Cano
Surface Characterization Of 316l Stainless Steel For Biomedical Applications, Lawrence Cano
Theses and Dissertations - UTB/UTPA
Stainless steel alloys play an important role in the field of biomaterials due to their exceptional corrosion resistance and biocompatibility. These alloys have the capability to enhance the quality of a human life by altering various structures of human physiology. The close proximity these alloys have with destructive body fluids, ion dissolution is a detrimental cause from the corrosion initiative and may cause unfavorable reactions. A view on developing an improved compatible surface for the human body leads to implementation of different chemical surface modifications used for creating features that must be corrosion resistant and biologically active without changing the …
Proper Orthogonal Decomposition For Incompressible And Compressible Flows, Seyed Milad Rafieinaini
Proper Orthogonal Decomposition For Incompressible And Compressible Flows, Seyed Milad Rafieinaini
Theses and Dissertations - UTB/UTPA
In this project, reduced order modelling technique has been used to investigate incompressible and compressible flows. At first, Proper Orthogonal Decomposition (POD), Singular Value Decomposition (SVD) and Principal Component Analysis (PCA) have been used to analyze pulsed jet flow as an incompressible flow and supersonic impinging jet as a compressible flow. Then, two flows have been investigated from physics point of view and finally the link between physics of flows and modes have been studied. All investigations have been done based on the given data from Particle Image Velocimetry (PIV). These data have been analyzed by using MATLAB®. Finally, the …
Aerodynamic Flow Field Characterization Of Airfoils With And Without Leading Edge Modifications, Oscar Hernandez
Aerodynamic Flow Field Characterization Of Airfoils With And Without Leading Edge Modifications, Oscar Hernandez
Theses and Dissertations - UTB/UTPA
Recently, much focus has been on comprehending the aerodynamic properties associated with the humpback whales pectoral fin. The perturbations found on its leading edge are believed to attribute to the humpbacks maneuverability significantly. These tubercles are assumed to be analogous to strakes on an aircraft, which generate large-scale vortices. More specifically, the vortices prompted by the leading edge increase the momentum exchange within the boundary layer, allowing the flow to remain attached at higher angles of attack, thus delaying stall and in turn increase lift by a passive means of reducing drag. The focus of this investigation is on characterizing …
Structural Integrity Of Conventional And Modified Railroad Bearing Adapters For Onboard Monitoring, Joseph Montalvo, Alexis Trevino, Arturo A. Fuentes, Constantine Tarawneh
Structural Integrity Of Conventional And Modified Railroad Bearing Adapters For Onboard Monitoring, Joseph Montalvo, Alexis Trevino, Arturo A. Fuentes, Constantine Tarawneh
Mechanical Engineering Faculty Publications and Presentations
This paper presents a detailed study of the structural integrity of conventional and modified railroad bearing adapters for onboard monitoring applications. Freight railcars rely heavily on weigh bridges and stations to determine cargo load. As a consequence, most load measurements are limited to certain physical railroad locations. This limitation provided an opportunity for an optimized sensor that could potentially deliver significant insight on bearing condition monitoring as well as load information. Bearing adapter modifications (e.g. cut outs) were necessary to house the sensor and, thus, it is imperative to determine the reliability of the modified railroad bearing adapter, which will …