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Ghods, MasoudEffect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation
Doctor of Engineering, Cleveland State University, 2017, Washkewicz College of Engineering
This dissertation explores the role of different types of convection on macrosegregation and on dendritic array morphology of two aluminum alloys directionally solidified through cylindrical graphite molds having both cross-section decrease and increase. Al- 19 wt. % Cu and Al-7 wt. % Si alloys were directionally solidified at two growth speed of 10 and 29.1 µm s-1 and examined for longitudinal and radial macrosegregation, and for primary dendrite spacing and dendrite trunk diameter. Directional solidification of these alloys through constant cross-section showed clustering of primary dendrites and parabolic-shaped radial macrosegregation profile, indicative of “steepling convection” in the mushy-zone. The degree of radial macrosegregation increased with decreased growth speed. The Al- 19 wt. % Cu samples, grown under similar conditions as Al-7 wt. % Si, showed more radial macrosegregation because of more intense “stepling convection” caused by their one order of magnitude larger coefficient of solutal expansion. Positive macrosegregation right before, followed by negative macrosegregation right after an abrupt cross-section decrease (from 9.5 mm diameter to 3.2 mm diameter), were observed in both alloys; this is because of the combined effect of thermosolutal convection and area-change-driven shrinkage flow in the contraction region. The degree of macrosegregation was found to be higher in the Al- 19 wt. % Cu samples. Strong area-change-driven shrinkage flow changes the parabolic-shape radial macrosegregation in the larger diameter section before contraction to “S-shaped” profile. But in the smaller diameter section after the contraction very low degree of radial macrosegregation was found. The samples solidified through an abrupt cross-section increase (from 3.2 mm diameter to 9.5 mm diameter) showed negative macrosegregation right after the cross-section increase on the expansion platform. During the transition to steady-state after the expansion, radial macrosegregation profile in locations close to the expansion was found to be “S-shaped”. This is attributed to the redistribution of solute-rich liquid ahead of the mushy-zone as it transitions from the narrow portion below into the large diameter portion above. Solutal remelting and fragmentation of dendrite branches, and floating of these fragmented pieces appear to be responsible for spurious grains formation in Al- 19 wt. % Cu samples after the cross-section expansion. New grain formation was not observed in Al-7 wt. % Si in similar locations; it is believed that this is due to the sinking of the fragmented dendrite branches in this alloy. Experimentally observed radial and axial macrosegregations agree well with the results obtained from the numerical simulations carried out by Dr. Mark Lauer and Prof. David R. Poirier at the University of Arizona. Trunk Diameter (TD) of dendritic array appears to respond more readily to the changing growth conditions as compared to the Nearest Neighbor Spacing (NNS) of primary dendrites.

Committee:

Surendra Tewari, Ph.D. (Advisor); Jorge Gatica, Ph.D. (Committee Member); Orhan Talu, Ph.D. (Committee Member); Rolf Lustig, Ph.D. (Committee Member); Kiril Streletzky, Ph.D. (Committee Member)

Subjects:

Aerospace Materials; Automotive Materials; Chemical Engineering; Condensed Matter Physics; Engineering; Fluid Dynamics; High Temperature Physics; Materials Science; Metallurgy

Keywords:

Directional Solidification; Natural Convection; Fluid Flow; Binary Alloys; Macrosegregation; Dendritic Array; Dendrite Morphology; Solutal Remelting; Thermosolutal Convection; Aluminum Alloy; Cross section Change

Hall, Brenton TaylorUsing the Non-Uniform Dynamic Mode Decomposition to Reduce the Storage Required for PDE Simulations
Master of Mathematical Sciences, The Ohio State University, 2017, Mathematical Sciences
Partial Differential Equation simulations can produce large amounts of data that are very slow to transfer. There have been many model reduction techniques that have been proposed and utilized over the past three decades. Two popular techniques Proper Orthogonal Decomposition and Dynamic Mode Decomposition have some hindrances. Non-Uniform Dynamic Mode Decomposition (NU-DMD), which was introduced in 2015 by Gueniat et al., that overcomes some of these hindrances. In this thesis, the NU-DMD's mathematics are explained in detail, and three versions of the NU-DMD's algorithm are outlined. Furthermore, different numerical experiments were performed on the NU-DMD to ascertain its behavior with repect to errors, memory usage, and computational efficiency. It was shown that the NU-DMD could reduce an advection-diffusion simulation to 6.0075% of its original memory storage size. The NU-DMD was also applied to a computational fluid dynamics simulation of a NASA single-stage compressor rotor, which resulted in a reduced model of the simulation (using only three of the five simulation variables) that used only about 4.67% of the full simulation's storage with an overall average percent error of 8.90%. It was concluded that the NU-DMD, if used appropriately, could be used to possibly reduce a model that uses 400GB of memory to a model that uses as little as 18.67GB with less than 9% error. Further conclusions were made about how to best implement the NU-DMD.

Committee:

Ching-Shan Chou (Advisor); Jen-Ping Chen (Committee Member)

Subjects:

Aerospace Engineering; Applied Mathematics; Computer Science; Mathematics; Mechanical Engineering

Keywords:

Fluid Dynamics; Fluid Flow; Model Reduction; Partial Differential Equations; reducing memory; Dynamic Mode Decomposition; Decomposition; memory; Non-Uniform Dynamic Mode Decomposition

Friedrich, Brian KarlAn Experimental Study of Volumetric Quality on Fluid Flow and Heat Transfer Characteristics for Two Phase Impinging Jets
Master of Science in Engineering, Youngstown State University, 2016, Department of Mechanical and Industrial Engineering
This study further expands the current knowledge of the relationship between heat transfer and fluid mechanics. Fluid flow and heat transfer characteristics of air-assisted water jet impingement was experimentally investigated under a fixed water flow rate condition. Water and air were the test fluids. The effects of volumetric quality (ß = 0 – 0.9) on the Nusselt number, hydraulic jump diameter, and pressure were considered. The results showed that stagnation Nusselt number, hydraulic jump diameter, and stagnation pressure increased with volumetric quality to a maximum value at 0.8 of the volumetric quality, and then decreased. The stagnation Nusselt number and hydraulic jump diameter of the air assisted water jet impingement are governed by the stagnation pressure. Based on the experimental results, a new correlation for the normalized stagnation Nusselt number and hydraulic jump are developed as a function of the normalized stagnation pressure alone. This research can be applied to further enhance the cooling of industrial applications, such as, cooling of electronics and processing of materials.

Committee:

Kyosung Choo, PhD (Advisor); Guha Manogharan, PhD (Committee Member); Jae Joong Ryu, PhD (Committee Member)

Subjects:

Experiments; Fluid Dynamics; Mechanical Engineering

Keywords:

impinging jet; Hydraulic Jump; two phase; two-phase; fluid flow; Heat transfer; jet impingement; Volumetric quality;

Chen, YingSensing and Energy Harvesting of Fluidic Flow by InAs Nanowires, Carbon Nanotubes and Graphene
Doctor of Philosophy, Case Western Reserve University, 2014, EMC - Mechanical Engineering
Energy harvesting using nanoscale devices is gaining increased attention because of the interest in scavenging power from the environment and redirecting it locally to power sensors or other devices. This Ph.D. dissertation focuses on nanostructured devices based on InAs nanowires (NWs), carbon nanotubes (CNTs) and graphene. The nanostructures were fabricated and incorporated into flow channels to investigate (i): the phenomenon of flow-induced voltage generation and its mechanism, (ii): the potential for nanosensor system applications and energy harvesting. In particular, the effects of fluid flow on electrical current/potential changes on nanostructured devices with/out source-drain voltages driving the device were investigated, and the voltage generations of NW, CNT and graphene-based energy harvesters were assessed. Indium Arsenide (InAs) nanowire (NW) and graphene field effect transistors (FETs) were incorporated into a microfluidic channel to detect the flow rate change as well as to harvest fluid flow energy for electric power generation. Discrete changes in the electric current through InAs NW FETs and graphene FETs were observed upon flow rate changes at steps of 1 ml/hr (equivalent to ~3 mm/s change in average linear velocity). The current also showed a sign change upon reversing flow direction. By comparing the response of device with and without a driving voltage between source-drain electrodes, it was concluded that the dominant contribution in the response was the streaming potential tuned conductance of NW/graphene. In the absence of a source-drain voltage, it was further demonstrated that ionic transport caused by the flow enabled generation of a ~mV electrical potential (or ~nA electrical current) inside the InAs NW per ml/hr increase in flow rate. This is most likely due to a charge dragging effect. Oriented multi-walled carbon nanotube (MWCNT) arrays mounted on a silicon (Si) substrate were subjected to a stagnation-type flow configuration in a cylindrical tube. The effect of local vs. bulk flow velocity on the flow-induced voltage was examined. Pressure, shear stress and viscous energy dissipation were estimated based on the stagnation-point flow model. The tip velocity at which the flow impinges on the tips of MCWNTs in the array showed a logarithmic dependence on voltage. It was shown that the flow-induced voltage can be significantly enhanced by increasing flow velocity and/or ionic strength of the fluid. The highest flow-induced voltage measured was 52 mV, and was generated from MWCNTs aligned perpendicular to the flow in 0.2 M NaCl and tip flow velocity of 4.05×10-5 m/s.

Committee:

Iwan Alexander (Advisor); Xuan Gao (Committee Member); Alexis Abramson (Committee Member); Ozan Akkus (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

energy harvesting; sensor; flow induced voltage; fluid flow; stagnation type flow; energy conversion; nanowire; nanotube; graphene; indium arsenide; carbon

Dabdoub, Shareef MajedApplied Visual Analytics in Molecular, Cellular, and Microbiology
Doctor of Philosophy, The Ohio State University, 2011, Biophysics
The current state of biological science is such that many sources of data are simply too large to be analyzed by hand. Furthermore, given the amazing breadth of investigation into the natural world, the potential for serious investigation from just mining heterogenous data sets is too rich to ignore. These two factors combined with the amount of computational power currently available make for ideal conditions from the perspective of visual analytics. Here we describe three computational projects focused on the visualization and analysis of data within the fields of microbial pathogenesis, cell biology, and molecular conformational dynamics. ProkaryMetrics is a new software package providing 3D reconstruction of fluorescent micrographs as well as various visual and statistical tools for analysis of bacterial biofilms. The software FIND is a new platform for promoting computational analysis and enhanced visualization of multicolor flow cytometry data. FIND provides users with user-friendly, cross-platform analysis software, while simultaneously providing algorithm designers a target for implementation. Finally, the Moflow project represents a new visual representation of atomic flow within molecules during conformational changes over time in a more intuitive sense than was previously possible.

Committee:

William Ray, PhD (Committee Chair); Sheryl Justice, PhD (Advisor); Shen Han-Wei, PhD (Committee Member); Luis Actis, PhD (Committee Member); Charles Daniels, PhD (Committee Member)

Subjects:

Bioinformatics; Biophysics; Computer Science

Keywords:

biofilms; urinary tract infection; volume visualization; visual analytics; flow cytometry; molecular dynamics; visualization; fluid flow; biophysics; computer science; bioinformatics; computational biology

Lee, YousubSimulation of Laser Additive Manufacturing and its Applications
Doctor of Philosophy, The Ohio State University, 2015, Welding Engineering
Laser and metal powder based additive manufacturing (AM), a key category of advanced Direct Digital Manufacturing (DDM), produces metallic components directly from a digital representation of the part such as a CAD file. It is well suited for the production of high-value, customizable components with complex geometry and the repair of damaged components. Currently, the main challenges for laser and metal powder based AM include the formation of defects (e.g., porosity), low surface finish quality, and spatially non-uniform properties of material. Such challenges stem largely from the limited knowledge of complex physical processes in AM especially the molten pool physics such as melting, molten metal flow, heat conduction, vaporization of alloying elements, and solidification. Direct experimental measurement of melt pool phenomena is highly difficult since the process is localized (on the order of 0.1 mm to 1 mm melt pool size) and transient (on the order of 1 m/s scanning speed). Furthermore, current optical and infrared cameras are limited to observe the melt pool surface. As a result, fluid flows in the melt pool, melt pool shape and formation of sub-surface defects are difficult to be visualized by experiment. On the other hand, numerical simulation, based on rigorous solution of mass, momentum and energy transport equations, can provide important quantitative knowledge of complex transport phenomena taking place in AM. The overarching goal of this dissertation research is to develop an analytical foundation for fundamental understanding of heat transfer, molten metal flow and free surface evolution. Two key types of laser AM processes are studied: a) powder injection, commonly used for repairing of turbine blades, and b) powder bed, commonly used for manufacturing of new parts with complex geometry. In the powder injection simulation, fluid convection, temperature gradient (G), solidification rate (R) and melt pool shape are calculated using a heat transfer and fluid flow model, which solves the mass, momentum and energy transport equations using the volume of fluid (VOF) method. These results provide quantitative understanding of underlying mechanisms of solidification morphology, solidification scale and deposit side bulging. In particular, it is shown that convective mixing alters solidification conditions (G and R), cooling trend and resultant size of primary dendrite arm spacing. Melt pool convexity in multiple layer LAM is associated not only with the convex shape of prior deposit but also with Marangoni flow. Lastly, it is shown that the lateral width of bulge is possibly controlled by the type of surface tension gradient. It is noted that laser beam spot size in the powder injection AM is about 2 mm and it melts hundreds of powder particles. Hence, the injection of individual particles is approximated by a lumped mass flux into the molten pool. On the other hand, for laser powder bed AM, the laser beam spot size is about 100 µm and thus it only melts a few tens of particles. Therefore, resolution of individual powder particles is essential for the accurate simulation of laser powder bed AM. To obtain the powder packing information in the powder bed, dynamic discrete element simulation (DEM) is used. It considers particle-particle interactions during packing to provide the quantitative structural powder bed properties such as particle arrangement, size and packing density, which is then an inputted as initial geometry for heat transfer and fluid flow simulation. This coupled 3D transient transport model provides a high spatial resolution while requiring less demanding computation. The results show that negatively skewed particle size distribution, faster scanning speed, low power and low packing density worsen the surface finish quality and promote the formation of balling defects. Taken together, both powder injection and powder bed models have resulted in an improved quantitative understanding of heat transfer, molten metal flow and free surface evolution. Furthermore, the analytical foundation that is developed in this dissertation provides the temperature history in AM, a prerequisite for predicting the solid-state phase transformation kinetics, residual stresses and distortion using other models. Moreover, it can be integrated with experimental monitoring and sensing tools to provide the capability of controlling melt pool shape, solidification microstructure, defect formation and surface finish.

Committee:

Dave Farson (Advisor); Wei Zhang (Advisor); Ramirez Antonio (Committee Member)

Subjects:

Fluid Dynamics; Materials Science

Keywords:

Laser Additive Manufacturing, Powder Packing, Melt Pool Shape, Balling Defects, Solidification Microstructure, Dendrite Arm Spacing, Fluid Flow, Marangoni Flow

Chinchore, Asmita CComputational Study of Savonius Wind Turbine
Master of Science in Mechanical Engineering, Cleveland State University, 2013, Fenn College of Engineering
This project involves study of 2-Blade and 3-Blade Savonius vertical wind turbines positioned at different orientations. For a 2-Blade turbine the orientations considered were 0 degree, 45 degree, 90 degree and 135 degree in reference to the direction of the prevailing wind and for the 3-Blade turbine the orientations taken into account were 0 degree, 30 degree, 60 degree and 90 degree in reference to the direction of the prevailing wind. The basic aim of this thesis was to study how the two designs are different from each other and which design produces more power when applied with constant wind velocity of 10mps. Computational Fluid Dynamics (CFD) analyses were conducted for every case to find out the torque and power generated by the turbines for each orientation. To ensure the accuracy of the results, CFD techniques were applied using Gambit 2.2.30 and Fluent 6.2.16. All cases were run using “transition-SST” flow model and the faces were meshed using `Quadrilateral Pave’ meshing scheme. The turbine was also tested for varying wind velocities of 5mps, 20mps, and 30mps for a constant orientation of turbine. The results were later compared and graphs were created for easy comparison of power and torque generated by turbines at different velocities. Maximum change in pressure occurs when 2-Blade turbine in perpendicular to direction of wind flow direction i.e. at 90 degree and when 3-Blade turbine is at 60 degree orientation. The 2-Blade Turbine generates higher value of torque (215.28 N) as compared to 3-Blade turbine, generating torque of value 110.92 N for any given constant wind velocity; 30mps in this case. This information can help the designer of the system to select the proper wind turbine considering the efficiency and stability along with other factors.

Committee:

Majid Rashidi, PhD (Committee Chair); Rama Gorla, PhD (Committee Member); Asuquo Ebiana, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Savonius Wind Turbine;Wind Turbines;2-Blade Turbine;3-Blade Turbine;CFD;Betz Limit;Fluid Flow Analysis;Ansys;Torque;Power

Ankrom, Linda SteeleMathematical modeling of converging fluid flow in the uniaxial die of the fixed boundary extrusion-orientation-crystallization process
Master of Science (MS), Ohio University, 1981, Chemical Engineering (Engineering)

Mathematical modeling of converging fluid flow in the uniaxial die of the fixed boundary extrusion-orientation-crystallization process

Committee:

John Collier (Advisor)

Subjects:

Engineering, Chemical

Keywords:

Extrusion-Orientation-Crystallization; Converging Fluid Flow; Uniaxial Die

MAGAR, YOGESH NARESHCONVECTIVE COOLING AND THERMAL MANAGEMENT OPTIMIZATION OF PLANAR ANODE-SUPPORTED SOLID OXIDE FUEL CELLS
MS, University of Cincinnati, 2006, Engineering : Mechanical Engineering
Convective heat and mass transfer in a planar, tri-layer, solid oxide fuel cell (SOFC) module is considered for a uniform supply of volatile species (80% hydrogen + 20% water vapor) and oxidant (20% oxygen + 80% nitrogen) to the electrolyte surface. With an Arrhenius electrochemical reaction rate, the coupled heat and mass transfer is modeled by steady incompressible fully-developed laminar flow in the interconnect ducts of rectangular cross section for both the anode-side fuel and cathode-side oxidant flows. The governing three-dimensional equations for mass, momentum, energy, and species transfer along with those for electrochemical kinetics are solved computationally using commercial CFD software. The homogeneous porous-layer flows, which are in thermal equilibrium with the solid matrix, are coupled with the electrochemical reaction rate to properly account for the flow-duct and anode/cathode interface heat/mass transfer. Parametric effects of rectangular flow duct aspect ratio and anode porous-layer thickness on the variations in species mass concentration and temperature distributions, flow friction factor, and convective heat transfer coefficient are presented. The combined effects of porous layer and electrochemical reaction are seen to alter the flow and heat transfer behavior of SOFC. The hydrodynamic and thermal behavior is characterized for effective performance and cooling, and interconnect channels of rectangular cross-section aspect ratio of ~ 2 are seen to provide optimal thermal management benefits. Parametric effects of flow duct cross-sectional shapes (triangle, trapezoid and, rectangle) and geometry along with heat transfer enhancing flow arrangements (offset-strip fin and wavy fin flows) are characterized by the variations in mass and temperature distributions, flow friction factor, and convective heat transfer coefficient. Though triangular cross section al interconnects showed lowest heat transfer coefficient it might be preferred de to its highest structural stability. Offset-strip flow arrangement has shown the best convective cooling and is probably the best interconnect design for the efficient thermal management in planar anode-supported SOFC.

Committee:

Dr. Raj Manglik (Advisor)

Subjects:

Engineering, Mechanical

Keywords:

Solid oxide fuel cells; Thermal analysis; Fluid flow; CFD; Compact Heat Exchangers; Electrochemistry

Chen, HuhuaVibration of a pipeline containing fluid flow with elastic support
Master of Science (MS), Ohio University, 1991, Civil Engineering (Engineering)
Vibration of a pipeline containing fluid flow with elastic support

Committee:

Shad Sargand (Advisor)

Subjects:

Engineering, Civil

Keywords:

Vibration; Pipeline Containing Fluid Flow; Elastic Support

Aliev, RuslanCFD Investigation of Heat Exchangers with Circular and Elliptic Cross-Sectional Channels
Master of Science in Mechanical Engineering, Cleveland State University, 2015, Washkewicz College of Engineering
Design of the fluid flow and heat transfer components utilizing the Computational Fluid Dynamics (CFD) is relatively new yet cheaper and accurate method that becomes popular and reliable today. In this thesis, design of a heat exchanger using CFD analysis technique is considered. A key investigation of this devise is the selection of the tubes and connection them to inlet and outlet manifolds. Correctly selected tube size and tube cross section impacts the heat exchanger performance. Thermal and hydrodynamic performance of the flow in circular and elliptic tubes connected to the inlet and outlet manifolds have been computationally investigated for maximum Figure of Merit. The tube with high Figure of Merit is the one with high heat transfer rate and low pressure drop. The tube has four different configurations of the cross section: a circular tube and three elliptic tubes with aspect ratios = 0.75, 0.50, and 0.25. All tubes are constrained to have the same wetted perimeter and the length, thus have the same heat transfer area. The tube is a smooth straight tube that has the length of 0.3048 m (12 in.) and wetted perimeter of 0.0798 m (3.1416 in.). The tube wall thickness is negligible. The contribution of the inlet and outlet manifolds is examined. A wide range of Reynolds numbers is covered, Re =100 (laminar flow), 10,000 (transitional flow), and 20,000 (turbulent flow). ANSYS FLUENT commercial code has been utilized in this investigation. The code was validated matching with experimental correlations (for developing hydrodynamic and thermal flow) available in the literature. The CFD simulation results were in agreement with the experimental correlation within 5%. This investigation started with simulating 12 different flow conditions inside the tubes without manifolds: three sets with four different tube options (as stated above) in each set. Each set represents the different flow regime: laminar transitional and turbulent with set Reynold number value, as noted earlier. All CFD simulation results were evaluated for their Figure of Merit (“Goodness” factor). The elliptic tube with aspect ratio = 0.25 showed the highest figure of merit for all cases of Re. In the following stage of this research the results of selected tube (aspect ratio = 0.25) was integrated with inlet and outlet manifolds. In this scenario only laminar and turbulent flow regimes were examined. The contribution of the inlet and outlet manifolds overall resulted a negative effect. The reasons of that impact are the following: (1) the inlet flow condition into the tube is no longer uniform (as was assumed in the earlier study), (2) the pressure drop in the manifolds are significantly higher than that in the tube. and (3) the tube length investigated is short. Despite significantly improved thermal characteristics of the tube flow after adding the manifolds, the magnitude of increased friction factor influenced the value of Figure of Merit.

Committee:

Mounir Ibrahim, PhD (Committee Chair); Majid Rashidi, PhD (Committee Member); Asuquo Ebiana, PhD (Committee Member)

Subjects:

Aerospace Engineering; Automotive Engineering; Mechanical Engineering; Nuclear Engineering; Petroleum Engineering

Keywords:

CFD analysis; circular and elliptic tube flow; heat exchanger; internal fluid flow; heat transfer; internal forced convection; figure of merit

MacDonald, Cody J.Hydrothermal Circulation During Slip on the Mohave Wash Fault, Chemehuevi Mountains, SE CA: Oxygen Isotope Constraints
Master of Science (MS), Ohio University, 2014, Geological Sciences (Arts and Sciences)
Fluids are likely significant during the life-cycle of low-angle normal faults (LANFs) as well as other fault systems, but the role of those fluids and their source at fault initiation are unclear. The Mohave Wash Fault (MWF), a LANF situated within the Chemehuevi Mountains core complex (SE CA), offers a well exposed site to evaluate this question. The MWF slipped 1-2 km during the Miocene before being denuded passively to the surface by extension localized on the higher-level Chemehuevi Detachment Fault. To evaluate fluid-rock interactions during the early slip on this fault system, δ18O values of whole rocks, quartz, and epidote were measured by CO2-laser fluorination and interpreted along with field and microscopic observations of fault rocks from this area. The MWF damage zone is variable in thickness and characterized by cracked granitic rocks hosting mineralized fractures, cohesive cataclasites, thin foliated shear zones, and rare pseudotachylite. δ18O of quartz hosted by undeformed granite ranges from 9.0-10.3‰, defining predeformation values. Foliated shear zones and quartz veins extend to lower δ18OQtz from 10.1-6.1‰, while cataclasites record the lowest δ18OQtz values down to 1.1‰. The δ18O values of epidote (from all types) ranges from 5.3‰ to - 0.4‰; the lowest values are generally in cataclasites. The shifts to lower δ18O are explained by interaction with heated, low δ18O fluids from an external source (evolved meteoric fluids or basin brines). Apparent temperatures from stable isotope thermometry on coexisting quartz and epidote (from 0.5 cc of rock) from the footwall are typically 50- 150°C higher than ambient footwall temperatures at 23 Ma (fault initiation) determined using 40Ar/39Ar closure temperatures (John and Foster, 1993). Temperatures defined by both methods increase in the paleodip direction. The temperature difference across the footwall estimated from Δ18O(Qtz-Ep) versus Ar/Ar closure temperatures either indicates the mineralization occurred prior to Ar/Ar closure or reflects localized upwelling of hot, deep seated fluids during slip along the MWF. Calculated δ18OH2O in equilibrium with mineral pairs decreases with lower temperature, consistent with influx of progressively lower δ18O fluids with decreasing temperature and depth.

Committee:

Craig Grimes, PhD (Advisor); Damian Nance, PhD (Committee Member); David Kidder, PhD (Committee Member)

Subjects:

Geochemistry; Geology

Keywords:

geology; oxygen isotopes; geochemistry; Chemehuevi Mountains; Low angel normal faults; Mohave Wash fault; fluid flow; faulting

Mihic, Stefan DragoljubCFD Investigation of Metalworking Fluid Flow and Heat Transfer in Grinding
Doctor of Philosophy in Engineering, University of Toledo, 2011, College of Engineering
Metalworking fluids have an exceptional role in grinding. Correct fluid application results in enhanced process stability, better work piece quality and tool life. This works aims to create and use Computational Fluid Dynamics (CFD) models in order to simulate the fluid flow and heat transfer in a grinding process, as a better alternative to many experiments that are expensive, time-consuming and with very limited ability. The features of created 2-D and 3-D models are described in detail, along with results obtained, and proposals for the future work. The results show very detailed distributions of temperatures, pressures and flow rates in and around the grinding region. By generating a very detailed picture of the grinding process itself, the data obtained is essential in studying the influence of the grinding fluid on the grinding process, as well as in determining the best fluid composition and supply parameters for a given application. The results agree well with experimental global flow rates and temperature values and show the feasibility of both 2-D and 3-D simulations in grinding applications, and performed parametric studies can be an useful tool in optimizing grinding processes.

Committee:

Sorin Cioc, Dr. (Advisor); Duane Hixon, Dr. (Committee Member); Dragan Isailovic, Dr. (Committee Member); Theo Keith, Dr. (Committee Member); Ioan Marinescu, Dr. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

CFD; Grinding; Fluid Flow; Heat Transfer; Metalworking Fluids

Hawkins, Jared B.Effect of Hydraulic Conductivity Heterogeneity on the Movement of Dense and Viscous Fluids in Porous Media
Master of Science, The Ohio State University, 2011, Geological Sciences

Currently, many remediation approaches are financially prohibitive or unrealistic to remediate deep, persistent dilute plumes of chlorinated ethylenes. This thesis outlines a new remediation approach designed to increase the residence time of in-situ dense chemical oxidants. This will be accomplished through the manipulation of the viscosity of the remediation chemicals and by taking advantage of natural aquifer heterogeneities. Dense chemical oxidants have advantages over more traditional remediation systems because they are relatively affordable, they require little maintenance, and they can be placed in targeted areas to maximize their effectiveness. Because they can be used to target specific areas, dense chemical oxidants have the ability to mitigate large, deep volatile organic compound (VOCs) plumes in aquifers. I postulate that the use of dense chemical oxidants can be enhanced further with the development of methods that will allow for the slow release of remediation chemicals over an extended period of time.

The first chapter identifies the problems addressed in this thesis. The second chapter analyzes the effect of heterogeneities on the movement of hypersaline solutions and demonstrates the modeling of dense, viscous solutions. The third chapter investigates the movement of dense solutions by gravity alone. The final chapter provides a general conclusion to the thesis. This thesis is part of a larger body of work funded by the Strategic Environmental Research and Development Program (SERDP), which is funded by the United States Department of Defense, Department of Energy, and Environmental Protection Agency.

In chapter 2, it was found that the lenticular media used in the experiments of Schincariol and Schwartz (1990) actually decreased solute residence time due to the high permeability of highly permeable lenses. These high permeability lenses also prevented the downward transport of plumes. One advantage found in this media, however, was that these lenses enhanced solute mixing. This is important because mixing helps spread remediation chemicals throughout larger portions of a contaminated aquifer. Results from chapter 2 also found that the variable-density flow and transport numerical model, MITSU3D (Ibaraki, 1998), was appropriate to model the dense, viscous solutions created by silica grout and that a long-term source of oxidant could be produced using silica grout to increase the viscosity of the remediation chemicals.

Results of chapter 3 analyzed the importance of permeability, instabilities, heterogeneous lenses, and source zone size on the movement of dense solutions by gravity alone in a media with alternating high and low permeable layers. It was found that the permeability of the less permeable layer played a significant role in plume development by slowing the downward transport of dense fluid. Lenses were also shown to significantly affect results by acting as conduits for the mixing and guidance of dense fluid. Instabilities and source zone size were shown to have only marginal effects on plume development.

Committee:

Franklin W. Schwartz, PhD (Advisor); Motomu Ibaraki, PhD (Committee Member); Garry D. McKenzie, PhD (Committee Member)

Subjects:

Environmental Geology; Geology; Hydrology

Keywords:

variable-density; fluid flow; remediation; density; viscosity; DNAPLs

Ugurlu, Ibrahim OlgunA New Method of Determining Pore Size Distribution (PSD) in Sandstones
MS, University of Cincinnati, 2015, Arts and Sciences: Geology
Transport properties, such as permeability, are significant in evaluating the production capacity of petroleum reservoir rocks. When a new reservoir is discovered, the most crucial parameter that needs to be determined by reservoir engineers is the rock permeability. Because the permeability of rocks is controlled not only by porosity, but also, and perhaps more importantly, by pore size distribution (PSD) and pore connectivity, a quantitative understanding of the PSD in petroleum reservoir rocks is critical in the evaluation of reservoir capacity. For example, two sandstones having similar porosities can have different permeabilities because of the variance in the PSD, degree of cementation, and tortuosity (PoA) of the porous media, all of which are critical to determining hydrocarbon production of the rocks. Within this context, a new method combining digital image analysis with an empirical equation was used to evaluate the pore geometry in thin sections of ten sandstone samples as a function of pore size distribution in three dimensions (3D) and tortuosity in 2D. Comparing the results of the PSD (3D), tortuosity (PoA), and the degree of cementation for ten samples shows that the extensive calcite cement in sample 1 is the primary control on porosity and permeability of the sample. On the other hand, the dominant pore diameter (R2=0.73), the value of the PSD slope (pore population density/mean length of pore, R2=0.70), and PoA (R2=0.64) are the leading controlling factors in permeability of the remaining nine samples. In this study, the samples having similar porosities (samples 3 and 5, and samples 4 and 6) have different distributions of pore sizes and different pore tortuosity, resulting in significant differences in the dominant pore diameters (149.3 µm and 42.6 µm, and 52.9 µm and 138.2 µm, respectively), the values of the PSD slope (–11 and –44, and –36 and –13, respectively) and PoA (52 mm-1 and 140 mm-1, and 118 mm-1 and 62 mm-1, respectively). These data reveal that permeability increases with increasing dominant pore diameter and the PSD slope, while PoA decreases with increasing permeability. In addition to providing an estimation of permeability for the sandstones with similar porosity, this method can be extended to evaluate pore size distribution as a function of depth in a drill core, percent of pores in each class interval and pore types and pore geometry.

Committee:

Attila Kilinc, Ph.D. (Committee Chair); Warren Huff, Ph.D. (Committee Member); Paul Potter, Ph.D. (Committee Member)

Subjects:

Petroleum Geology

Keywords:

pore size distribution;permeability;tortuosity;oil production rate;fluid flow capacity;dominant pore diameter

QUET, Pierre-Francois DA ROBUST CONTROL THEORETIC APPROACH TO FLOW CONTROLLER DESIGNS FOR CONGESTION CONTROL IN COMMUNICATION NETWORKS
Doctor of Philosophy, The Ohio State University, 2002, Electrical Engineering
In this dissertation a control theoretic approach is taken to design and analyze various flow controllers for congestion control in communication networks. First, a robust controller is designed for explicit-rate congestion control in single-bottleneck network. The controller guarantees stability robustness with respect to uncertain time-varying multiple time-delays in different channels, brings the queue length of the bottleneck node to a desired value asymptotically and satisfies a weighted fairness condition. The use of the outgoing link capacity is further investigated to improve performance. Also, some variations on a linear model of Active Queue Management supporting Transmission Control Protocol flows are used to design a robust AQM controller, and to analyse the performance and stability of Multi-Level ECN and Traffic-load based AQM schemes.

Committee:

Hitay Ozbay (Advisor)

Keywords:

Communication networks; Flow control; Uncertain time-varying multiple time-delays; Active queue management; Fluid flow model

Hug, Scott A.Computational Fluid Dynamics Modeling of a Gravity Settler for Algae Dewatering
Master of Science in Chemical Engineering, Cleveland State University, 2013, Fenn College of Engineering
Algae are the future of lipid sources for biodiesel production. Algae can produce more biodiesel than soybean and canola oil and can be grown in more diverse locations. Algae concentrations are naturally around 0.1% by weight. Enough water must be removed for the algae level to reach 5%, the minimum concentration in which lipids can be used in the transesterification process for biofuel production is 5%. Current dewatering methods involve the use of settling tanks and centrifugation. The costs of centrifugation limit the commercial viability of algae based biodiesel. A novel inclined gravity settler design at Cleveland State University is analyzed in this project. A major difference between this and a traditional gravity settler is that the inlet of this gravity settler is at the top, whereas traditional gravity settlers have inlets at the bottom. A computational fluid dynamics model for the system has been developed to allow the simulations of fluid flow and particle trajectories over time. These simulations determine the optimal conditions for algae dewatering. Results show that the concentration increase of algae is largely dependent on the settler's angle of inclination, inlet flow rate, and the split ratio of water between the overflow (predominantly water) and underflow (concentrated algae) outlets. A 50-fold concentration increase requires multiple settlers set up in series. A two- or three-settler design is sufficient to increase algae concentration the desired level.

Committee:

Jorge Gatica, PhD (Committee Chair); Joanne Belovich, PhD (Committee Member); Chandra Kothapalli, PhD (Committee Member); Dhananjai Shah, PhD (Committee Member)

Subjects:

Alternative Energy; Chemical Engineering

Keywords:

Algae; Dewatering; Gravity settler; Inclined gravity settler; Fluid dynamics; Fluid flow; Particle trajectories;

Anderson, Eric JamesBRIDGING THE GAP IN UNDERSTANDING BONE AT MULTIPLE LENGTH SCALES USING FLUID DYNAMICS
Doctor of Philosophy, Case Western Reserve University, 2007, Mechanical Engineering
Fluid flow through the network of pathways in bone tissue is hypothesized to play an integral role in transducing external mechanical forces from the skeletal level down to the cells embedded deep within bone tissue. Communicating these external forces to bone cells is thought to be the mechanism by which bone is regenerated, and thus has major implications in fighting bone disease as well as repairing defects or damage to the tissue. This research pursues the role of fluid flow in bone remodeling and looks to bridge the gap between tissue and cellular level knowledge using computational fluid dynamics modeling of Navier-Stokes equations as well as experimental validations of applicable models. Using physiologic model geometries of increasing complexity, the following work predicts currently immeasurable propeties of this tissue such as permeability or cell communication, as well as the resultant mechanical forces as they exist at the cellular and subcellular levels. The mechanical environment of the osteocyte is described, where the mode and magnitude of force on the cell varies spatio-temporally. Both the hydrodynamic pressure and imparted shear stress are found on the cell surface, where the cell body experiences a nearly constant pressure and virtually zero shear stress while the cell processes are exposed to high gradients of both shear stress and pressure. This differentiation between types and location of forces has possible implications in cell physiology and the types of receptors or mechanosensors present on the cell. In addition, along the cell processes, which radiate from the cell body, subcellular geometries near the lower continuum-limit yield small discontinuities in the annular wall that are foundt o amplify peak shear stresses up to five times that of previous predictions. This result gives insight into a major paradox that has existed in bone and suggests a bridge between theoretical predictions and laboratory measurements of the necessary mechanical force for cell stimulation, where previous in vitro measurements have been an order of magnitude higher than in vivo predictions. This knowledge of the cell's mechanical environment is used to improve and design applications for laboratory cell studies and tissue growth in vitro.

Committee:

Melissa Knothe Tate (Advisor)

Keywords:

mechanotransduction; bone fluid flow; computational fluid dynamics; osteocyte