Mechanical Engineering Commons^™

Oil Droplet Behavior At A Pore Entrance In The Presence Of Crossflow: Implications For Microfiltration Of Oil-Water Dispersions, Nikolai V. Priezjev, Tohid Darvishzadeh, Volodymyr V. Taravara

Mechanical and Materials Engineering Faculty Publications

The behavior of an oil droplet pinned at the entrance of a micropore and subject to clossflow-induced shear is investigated numerically by solving the Navier-Stokes equation. We found that in the absence of crossflow, the critical transmembrane pressure required to force the droplet into the pore is in excellent agreement with a theoretical prediction based on the Young-Laplace equation. With increasing shear rate, the critical pressure of permeation increases, and at sufficiently high shear rates the oil droplet breaks up into two segments. The results of numerical simulations indicate that droplet breakup at the pore entrance is facilitated at lower …

Heterogeneous Relaxation Dynamics In Amorphous Materials Under Cyclic Loading, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

Molecular dynamics simulations are performed to investigate heterogeneous dynamics in amorphous glassy materials under oscillatory shear strain. We consider three-dimensional binary Lennard-Jones mixture well below the glass transition temperature. The structural relaxation and dynamical heterogeneity are quantified by means of the self-overlap order parameter and the dynamic susceptibility. We found that at sufficiently small strain amplitudes, the mean square displacement exhibits a broad subdiffusive plateau and the system undergoes nearly reversible deformation over about 104 cycles. Upon increasing strain amplitude, the transition to the diffusive regime occurs at shorter time intervals and the relaxation process involves intermittent bursts of large …

Anisotropic Compositional Expansion And Chemical Potential For Amorphous Lithiated Silicon Under Stress Tensor, Valery I. Levitas, Hamed Attariani

Mechanical and Materials Engineering Faculty Publications

Si is a promising anode material for Li-ion batteries, since it absorbs large amounts of Li. However, insertion of Li leads to 334% of volumetric expansion, huge stresses, and fracture; it can be suppressed by utilizing nanoscale anode structures. Continuum approaches to stress relaxation in Li_xSi, based on plasticity theory, are unrealistic, because the yield strength of Li_xSi is much higher than the generated stresses. Here, we suggest that stress relaxation is due to anisotropic (tensorial) compositional straining that occurs during insertion-extraction at any deviatoric stresses. Developed theory describes known experimental and atomistic simulation …

A Computational Approach To Simulating The Performance Of A 24-Hour Solar-Fuel Cell-Hydrogen Electric Power Plant, Michael K. Gustafson

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World energy demand has risen from about 375 exajoules (EJ) in 1990 to around 600 EJ today. The Energy Information Administration predicts that by the year 2035, this figure will rise to around 800 EJ. This places large stresses on the electric generation infrastructure. Increasingly this demand is being met by renewable energy sources. There are several reasons this is the case. The prices of renewables are dropping quickly and reaching grid parity in more regions. Utilizing renewable energy generation can help achieve energy security: adverse weather or military conflicts are less likely to impact supply routes when energy is …

Nanomaterials Synthesis, Applications, And Toxicity 2012, Mallikarjuna Nadagouda, Dionysios Demetriou Dionysiou, Darren A. Lytle, Thomas F. Speth, Sharmila M. Mukhopadhyay

Mechanical and Materials Engineering Faculty Publications

Nanotechnology presents new opportunities to create better materials and products. Nanomaterials find wide applications in catalysis, energy production, medicine, environmental remediation, automotive industry, and other sectors of our society. Nanomaterial-containing products are already available globally and include automotive parts, defense application, drug delivery devices, coatings, computers, clothing, cosmetics, sports equipment, and medical devices. This special issue includes emerging advances in the field, with a special emphasis given to nanomaterial synthesis and applications.

A Comparative Study Of Three Different Chemical Vapor Deposition Techniques Of Carbon Nanotube Growth On Diamond Films, Betty T. Quinton, Paul N. Barnes, Chakrapani V. Varanasi, Bang-Hung Tsao, Kevin J. Yost, Sharmila M. Mukhopadhyay

Mechanical and Materials Engineering Faculty Publications

This paper compares between the methods of growing carbon nanotubes (CNTs) on diamond substrates and evaluates the quality of the CNTs and the interfacial strength. One potential application for these materials is a heat sink/spreader for high-power electronic devices. The CNTs and diamond substrates have a significantly higher specific thermal conductivity than traditional heat sink/spreader materials making them good replacement candidates. Only limited research has been performed on these CNT/diamond structures and their suitability of different growth methods. This study investigates three potential chemical vapor deposition (CVD) techniques for growing CNTs on diamond: thermal CVD (T-CVD), microwave plasma-enhanced CVD (MPE-CVD), …

Design And Improve Energy Efficiency And Functionalities Of Electrical Wheelchairs, Dewei Guan

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There are millions of people who have lost their abilities to walk and wheelchairs offer the ONLY opportunities for their interactions with people and environments outside their houses. These individuals are becoming more and more eager to adapt modern technologies on their wheelchairs to improve quality of social life and the life of freedom. However, most available electric wheelchairs, driven by traditional lead-acid batteries and gear motors, are heavy and bulky in design with low energy efficiency, limited travel radius, and scarce communication/navigation functionalities. This project is to design and prototype an electric wheelchair that is lighter, more flexible in …

Steps In The Development Of A Full Particle-In-Cell, Monte Carlo Simulation Of The Plasma In The Discharge Chamber Of An Ion Engine, Bryan James Penkal

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The design and development of ion engines is a difficult and expensive process. In order to alleviate these costs and speed ion engine development, it is proposed to further develop a particle-in-cell (PIC), Monte-Carlo collision (MCC) model of an ion engine discharge chamber, which has previously been worked on by the Wright State Ion Engine Modeling Group. Performing detailed and accurate simulations of ion engines can lead to millions of dollars in savings in development costs.

In order to recognize these savings more work must be done on the present day models used to simulate ion engine performance. The work …

Bull's-Eye Structure With A Sub-Wavelength Circular Aperture, Masoud Zarepoor

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This research focuses on improving the spatial resolution of terahertz (THz) imaging. Using a sub-wavelength aperture in a metal ground plane is the most common way to improve the spatial resolution, but a sub-wavelength aperture has low radiation transmission. To increase the radiation transmission of a sub-wavelength aperture, periodic circular grooves were put in the metal around the aperture. The sub-wavelength circular aperture and the periodic circular grooves around it are known as the bull's-eye structure. The bull's-eye structure shows high radiation transmission at its design frequency, and it also has sub-wavelength spatial resolution. This research designed the bull's-eye structure …

Structural-Acoustic Analysis And Optimization Of Embedded Exhaust-Washed Structures, Ryan N. Vogel

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The configurations for high speed, low observable aircraft expose many critical areas on the structure to extreme environments of intense acoustic pressure loadings. When combined with primary structural and thermal loads, this effect can cause high cycle fatigue to aircraft skins and embedded exhaust system components. In past aircraft design methods, these vibro-acoustic loads have often been neglected based on their relatively small size compared to other thermal and structural loads and the difficulty in capturing their dynamic and frequency dependent responses. This approach is insufficient for effective advanced designs of complex aerospace structures, such as internal ducted exhaust systems …

Dynamic Simulation Of Turbine Engine Used With Molten Carbonate Fuel Cell For Power Generation In The Megawatt Range, Carlos Eduardo Gutierrez

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Molten carbonate fuel cells (MCFC) have a high operating temperature of approximately 650° C (1200° F) to achieve sufficient conductivity of its carbonate electrolyte. Therefore, a gas turbine engine coupled with a MCFC is desirable since the turbine engine can be used to provide hot gas to the cathode, and the cathode gas residue can be used to raise the temperature of the natural gas and water vapor mixture (fuel) before it enters the MCFC at the anode. Dynamic models of a hybrid power plant consisting of a gas turbine engine and a MCFC with their respective components were developed …

Shock Correlation Investigation In A Gaseous Fueled Axisymmetric Scramjet Flowpath, Jaime Omar Larios-Barbosa

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A pressure-based investigation was conducted on a gaseous fueled axisymmetric scramjet flowpath in Research Cell 22 located at Wright Patterson AFB. The investigation followed the work performed by Waltrup and Billig using combustion data to validate the form of the correlation in an attempt to achieve a good predictive tool for isolator length. Two years of axial wall pressure data using Mach values of 1.8 and 2.2 were analyzed in this investigation. The combustion data was shown to follow the same quadratic distribution show in Waltrup and Billig's work with the data being shifted to the right relative to the …

Effect Of Process Variables On Sub-Melt Thermal Behavior And Solid-State Phase Transformations In Beam-Based Additive Manufacturing Of Ti-6al-4v, Heather N. Doak

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The success of laser and electron beam-based fabrication processes for additive manufacture and repair applications requires the ability to control melt pool geometry while maintaining a consistent and desirable microstructure. Previous work has employed a process map approach to link melt pool geometry to solidification microstructure (grain-size and morphology) in beam-based fabrication of Ti-6Al-4V. The current work extends the approach to investigate the effects of process variables on solid-state phase transformations below the solidification temperature through Finite Element Modeling, the 3-D Rosenthal Solution, and experimentation. Process maps for solid-state microstructure could be used to help maintain consistent and reliable mechanical …

Wing Damage Effect On Dragonfly's Aerodynamic Performance During Takeoff, Kuo Gai

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Insect wing damage resulted from living environment or predation commonly happens in nature. This usually results in deterioration of insect's flight performance and as a consequence, the insect needs adjustment of flapping wings to compensate the effect from the wing loss. In this study, a dragonfly (Erythemis simpliciolis) with and without wing loss is chosen to study the change of aerodynamic performance of flapping wings. Three cases including flight with intact wings (IW), flight with one-sided forewing damage (OFD), and flight with double-side forewing damage (DFD) are determined. An integrated study using high-speed photogrammetry, three-dimensional surface reconstruction, and direct numerical …

An Experimental Investigation On The Control Of Tip Vortices From Wind Turbine Blade, Zhe Ning

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Wind turbine dynamics, wake effects and environmental impacts have been identified the most significant research topics needed for wind resource characterization and wind power generation. Among these issues, tip vortices generated from the blade tip have been recognized as a substantial resource for the turbulent wake flow as well as the aerodynamic noise emission from a wind turbine. An experimental study is conducted to characterize the evolution of the tip vortices downstream of a well-designed horizontal axis wind turbine (HAWT) model. In addition to measuring dynamic wind loads (both aerodynamic forces and moments) and power output from the wind turbine …