Doctor of Philosophy (PhD), Ohio University, 2019, Chemical Engineering (Engineering and Technology)

The impact of fluid flow on the mechanical integrity and protectiveness of corrosion product layers formed on the surface of carbon steel pipelines is a crucial aspect of corrosion in CO2/H2S environments typically encountered in oil and gas production. Produced fluids may travel inside pipelines at velocities that can generate high shear stresses on the pipe wall. The effect of shear stress on the development of corrosion product layers, and more specifically iron sulfide layers, or the retention of already developed layers is not known. In addition, high fluid velocities generate high mass transfer rates which impact the corrosion behavior of carbon steel substrates. The effect of high mass transfer rates on the characterization of iron sulfide layers is also yet to be fully understood. The goal of this project is to explore ways to identify the individual contributing effects of wall shear stress and mass transfer rate to the development and retention of iron sulfide layers in representative flow conditions and relate this to the corrosion behavior of a carbon steel substrate. This will help characterize the protectiveness, or lack thereof, of FeS layers and enable the selection of appropriate asset integrity management program. The first part of this project focused on the development of experimental test setups, the glass cell with impeller flow and the channel cell in the single-phase flow loop, which enable representative flow conditions and control of water chemistry. The flow in these systems was characterized using electrochemical methods by developing a Sherwood correlation. The associated shear stress impacting the specimen surface was also characterized through computational fluid dynamics (CFD) techniques. The developed mass transfer correlations were used to model the experimentally determined corrosion rate results successfully. In the next part of this project, the glass cell with an impeller flow experimental setup was used to study the role (open full item for complete abstract)

Committee: Marc Singer (Advisor); Nesic Srdjan (Committee Member); Lopez Dina (Committee Member); Katherine Cimatu (Committee Member); John Staser (Committee Member) Subjects: Chemical Engineering; Chemistry; Engineering; Experiments; Fluid Dynamics; Materials Science; Mechanical Engineering

Doctor of Philosophy (PhD), Ohio University, 2014, Mechanical Engineering (Engineering and Technology)

Three-phase gas-oil-water flow is a common occurrence in the oil and gas industry. The presence of water in the pipeline can lead to internal corrosion if the free water, dissolved with corrosive species, comes into contact with the wall surface, a scenario known as 'water wetting.' With the introduction of a gas phase, the flow dynamics become much more complicated due to the varying degree of spatial distribution of the immiscible fluids. The present work addresses how the addition of a gas phase to the oil-water flow can change the flow dynamics and surface wetting behavior. The work mainly focuses on the hydrodynamic aspects of the flow and how they may affect the surface wetting in pipe flow. Experimental work was first carried out on oil-water systems to investigate flow patterns and surface wetting behavior in order to establish a baseline for the subsequent measurement of three-phase flow into which CO2 gas was introduced. The experiments were conducted in a large scale 0.1 m ID flow loop. Test fluids used were light model oil LVT200 and 1 wt.% aqueous NaCl. Flow pattern images were visually captured with a high speed video camera and surface wetting behavior was measured using conductivity pins. In oil-water flow, flow patterns can be divided into two broad categories dependent on whether the two immiscible liquids are dispersed or separated. Under those flow conditions, the surface wetting behavior can be categorized into four types of wetting regimes based on the intermittency of the wetting behavior as measured by the conductivity pins. In three-phase gas-oil-water flow, the effects of gas added to the oil-water system were investigated. Flow patterns and surface wetting were quantified at various liquid velocities, gas velocities and water cuts. At low water cut, the wetting results showed that adding the gas phase can help to keep water off the pipe wall, leading to oil wetting. At high water cut, water wetting prevailed and adding gas did n (open full item for complete abstract)

Committee: Srdjan Nešic PhD (Advisor) Subjects: Chemical Engineering; Fluid Dynamics; Mechanical Engineering; Petroleum Engineering

Doctor of Philosophy (PhD), Ohio University, 2010, Chemical Engineering (Engineering and Technology)

The presence of water, even in small amounts, is often the cause of internal corrosion problems in crude oil transportation. Understanding the factors influencing steel pipeline corrosion rates is a safety as well as an economic matter. The objective of this dissertation is to quantify the effects that are known to have an influence on corrosion in crude oil-brine flow. The first effect is the corrosiveness of the brine. Crude oil's compounds can partition between the oil phase and the water phase to create brines with inhibitive or corrosive properties. The second effect is related to which phase wets the pipe wall. This depends on steel wettability and also on the flow pattern. Crude oil's polar compounds can change the steel hydrophilic surface nature. They also change the flow properties. The problem has been investigated at the Institute for Corrosion and Multiphase Technology at Ohio University on a small scale with specifically designed experiments as well as on a large scale, in a 60 meter-long flow loop loaded with 1600 gallons of oil and water. Results show that only a small percentage of the crude oil's complex chemistry controls its corrosion inhibitive and wettability properties. The knowledge generated from these experiments can be used as a useful reference for corrosion engineers and pipeline operators to maintain oil-water flow systems under corrosion-free conditions.

Committee: Srdjan Nesic PhD (Committee Chair); Michael Prudich PhD (Committee Member); Jeffrey Rack PhD (Committee Member); Howard Dewald PhD (Committee Member); Douglas Goetz PhD (Committee Member) Subjects: Chemical Engineering; Chemistry

Doctor of Philosophy (PhD), Ohio University, 2020, Industrial and Systems Engineering (Engineering and Technology)

A supply chain is a network of suppliers, production, or manufacturing facilities, retailers, and transportation channels which are structured to acquire supplies, produce new products, and distribute the finished products to retailers and customers. Closed Loop Supply Chain (CLSC) networks incorporate the flow of the returned, used, or recycled products from the customers through the retailers to the manufacturing, recycling, or refurbishing facilities to support managing the full lifecycle of the products. Social Network Analysis (SNA) has been developed to identify and analyze the patterns in social networks. SNA is used as a theoretical framework for better understanding of social networks by characterizing the structure of a network in terms of nodes and links. SNA is applied to various types of networks including telecommunication networks, protein interaction networks, animal disease epidemics, and customer interaction and analysis. Although SNA is a powerful method to study networks in many areas, it has not been comprehensively applied to supply chain networks. Likewise, there is no application and interpretation of SNA metrics in CLSCs. In this study, SNA metrics are introduced and interpreted for components in CLSC networks and forward and reverse logistic activities. Correspondingly, a decision making tool is developed based on selected SNA metrics for comparing alternative network designs in terms of network reliability and balance of the flows.

Committee: Saeed Ghanbartehrani (Advisor); Gary Weckman (Committee Member); Tao Yuan (Committee Member); Vardges Melkonian (Committee Member); Benjamin Sperry (Committee Member) Subjects: Industrial Engineering; Information Technology; Management

Doctor of Philosophy, University of Akron, 2013, Electrical Engineering

Although Photovoltaic (PV) sources have been around for a long time, their contribution in power systems is limited due to factors related to their low efficiency and the complexity of their control. In this dissertation, efficient and effective control algorithms are developed for single phase microgrid-connected photovoltaic (MCPV) sources. The developed algorithms are divided into three levels based on their scopes. Level-1 includes algorithms that perform tasks within the MCPV control system. Level-2 coordinates the parts of the MCPV control system. Level-3 analyzes microgrids and the interactions among their sources. In level-1, algorithms are developed for phase-locked loop and harmonics estimation. The available algorithms for these tasks are computationally demanding and are sensitive to the disturbances that take place in microgrids. Efficient, accurate and robust algorithms are therefore developed in this dissertation for these tasks. The real power control of MCPV sources is covered in level-2. To operate effectively, the MCPV sources need to produce the maximum possible amount of power and to participate in regulating the voltage and frequency of the microgrid. The MCPV control system can be configured in different ways to achieve these tasks, however the performance of some of the configurations is unsatisfactory. A novel configuration for the MCPV controllers is proposed to perform the required tasks effectively without a need of supervisory controllers. Moreover, a procedure is developed to tune the controllers and ensure the stability of the MCPV sources. In level-3, an algorithm is developed to perform load flow analysis (LFA) for microgrids. The developed LFA is used in an optimization process that tunes the droop parameters such that the load is fairly distributed among the sources. The optimization problem takes into consideration the nature of the MCPV sources by adjusting their parameters adaptively such that their reactive powers increase (open full item for complete abstract)

Committee: Yilmaz Sozer Dr. (Advisor); Malik Elbuluk Dr. (Advisor); Tom Hartley Dr. (Committee Member); Ping Yi Dr. (Committee Member); Alper Buldum Dr. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2012, Aero/Astro Engineering

Detailed investigation of the NACA 643-618 is obtained at a Reynolds number of 6.4x104 and angle of attack sweep of -5° < α < 25°. The baseline flow is characterized by four distinct regimes depending on angle of attack, each exhibiting unique flow behavior. Active flow control is exploited from a row of discrete holes located at five percent chord on the upper surface of the airfoil. Steady normal blowing is employed at four representative angles; blowing ratio is optimized by maximizing the lift coefficient with minimal power requirement. The range of effectiveness of pulsed actuation with varying frequency, duty cycle and blowing ratio is explored. Pulsed blowing successfully reduces separation over a wide range of reduced frequency (0.1-1), blowing ratio (0.5–2), and duty cycle (0.6–50%). A phase-locked investigation, by way of particle image velocimetry, at ten degrees angle of attack illuminates physical mechanisms responsible for separation control of pulsed actuation at a low frequency and duty cycle. Temporal resolution of large structure formation and wake shedding is obtained, revealing a key mechanism for separation control. The Kelvin-Helmholtz instability is identified as responsible for the formation of smaller structures in the separation region which produce favorable momentum transfer, assisting in further thinning the separation region and then fully attaching the boundary layer. Closed-loop separation control of an oscillating NACA 643-618 airfoil at Re = 6.4x104 is investigated in an effort to autonomously minimize control effort while maximizing aerodynamic performance. High response sensing of unsteady flow with on-surface hot-film sensors placed at zero, twenty, and forty percent chord monitors the airfoil performance and determines the necessity of active flow control. Open-loop characterization identified the use of the forty percent sensor as the actuation trigger. Further, the sensor at twenty percent chord is used to distinguish between (open full item for complete abstract)

Committee: Jeffrey Bons Dr. (Advisor); Mohammad Samimy Dr. (Committee Member); Jen-Ping Chen Dr. (Committee Member); Andrea Seranni Dr. (Committee Member) Subjects: Aerospace Engineering; Fluid Dynamics