PhD, University of Cincinnati, 2018, Engineering and Applied Science: Aerospace Engineering

Interaction between a deformable elastic body and an internal or external fluid flow alters the flow pattern. This dissertation describes the effects of elasticity on flow in physiological scenarios. The first part of the thesis describes the influence of soft tissue compliance on flow in the upper airways of pediatric Down syndrome (DS) patients and adolescent Polycystic-Ovarian syndrome patients with obstructive sleep apnea (OSA). Computational fluid dynamics (CFD) of airflow is performed in pre and post-operative geometries of the DS pediatric airway to evaluate effectiveness of a surgery and address the importance of including the subject-specific tissue compliance. A tube law approach and a novel image analysis method are then presented to evaluate the circumferential variation in airway compliance for DS patients. An iterative finite element method is then described to non-invasively estimate patient-specific mechanical properties of the upper airway in these patients. The estimated mechanical properties for a single patient are applied to simulate airway obstruction during inspiratory airflow, before and after surgery. Sensitivity to different flow variables is analyzed and an operating map is created to establish the relationship between tissue elasticity and volumetric airflow. The necessity for performing fluid-structure interaction (FSI) in PCOS subjects with OSA is illustrated through a series of strain maps of upper airway tissue. An inverse methodology based on FSI simulations is described to characterize the soft-palate stiffness in these subjects. Differences in pre and post-operative airflow patterns and tissue motion in a PCOS patient are described using computational modeling and compared with the same for a healthy individual. The second part of the study describes computational FSI modeling of aortic blood flow in Turner syndrome (TS). A continuous measurement tool is developed to automatically compute the longitudinal variation in maximum aort (open full item for complete abstract)

Committee: Ephraim Gutmark Ph.D. (Committee Chair); Shaaban Abdallah Ph.D. (Committee Member); Iris Gutmark-Little (Committee Member); Mark Turner Sc.D. (Committee Member) Subjects: Aerospace Materials

Master of Science, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1960, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy (Ph.D.), University of Dayton, 2023, Aerospace Engineering

Turbomachinery components, such as the low pressure turbine, are highly complex rotating machines, therefore, conducting fundamental fluid mechanics studies in them is exceedingly difficult. For this reason, testing is generally completed in facilities such as linear cascades, like the one present in the Low Speed Wind Tunnel Facility at AFRL, which typically utilize a low freestream turbulence intensity, when in reality, the freestream turbulence intensity in a full, rotating low pressure turbine is likely much higher. Slightly elevating the freestream turbulence intensity (e.g., 3%) typically improves the Reynolds-lapse characteristics of a blade profile by affecting the transition process, reducing the detrimental effects of laminar boundary layer separation, and shifting the knee in the loss curve. Front loaded blades are more resistant to separation, however, they can experience high losses in the endwall region due to the complex vortical structures present. Therefore, a better understanding whether high levels of freestream turbulence intensity will increase the overall losses generated in the passage is important. An intial study with a jet based active grid was completed on the L2F blade. Based of the insight gained from that study, a new mechanical agitator based active grid was implemented into a linear cascade of L3FHW-LS blades in order to more effectively study how elevated FSTI impacts the endwall flow behavior and loss production. Coefficient of pressure measurements, three planes of SPIV, two additional planes of flow visualization, and three planes of total pressure loss measurements were collected. Impacts of incoming turbulence on the endwall losses as well as the endwall flow structures were assessed.

Committee: Markus Rumpfkeil (Advisor); Christopher Marks (Committee Member); Sidaard Gunasekaran (Committee Member); John Clark (Committee Member) Subjects: Aerospace Engineering

Doctor of Philosophy, The Ohio State University, 2022, Chemical Engineering

Drag reduction (DR) by additives typically involves the use of either high molecular weight polymer or surfactants, and can reduce turbulent pressure losses in pipes by up to 90%. These additives, particularly high polymers, have seen considerable use in increasing the throughput of crude oil pipelines. Surfactant additives, while even more effective than their polymer cousins, have not seen widespread adoption despite their applicability to recirculating district heating or cooling networks. Due to their effects on the turbulent structure of pipe flow, drag reducing additives also result in the loss of radial mixing, and thus the suppression of convective heat transfer. This is referred to as the 'heat transfer reduction' (HTR) effect. Under normal conditions, drag reducing additives can reduce convective heat transfer in even greater amounts than they do turbulent pressure losses. Much of the recent research in the field of surfactant drag reduction has, therefore, been dedicated to the mitigation of heat transfer reduction. In this work, two projects are presented which successfully achieve this goal. In the first, a constricted heat exchanger is used to locally increase the shear stresses experienced by the working fluid. Simultaneously, a `weak' drag reducing solution comprised of quaternary ammonium salts with saturated tails 16 and 14 carbons in length and the counterion 3-chlorobenzoic acid. In conjunction with the constricted heat exchanger, this mixture is able to simultaneously generate high (>60%) DR and low (>30%) HTR over a range of flow rates and temperatures. Other unique properties of the system are examined, including switchability and hysteresis. The second study involves the design and application of 'gentle' static mixers. Rather than being designed to destroy the micellar structure thought to be responsible for DR, these mixers are intended to periodically disrupt the thermal boundary layer in the heat exchanger, thus improving heat tr (open full item for complete abstract)

Committee: Kurt Koelling (Advisor); Jim Rathman (Committee Member); Stuart Cooper (Committee Member); Andrew Maxson (Committee Member) Subjects: Chemical Engineering; Energy; Engineering; Fluid Dynamics

Master of Sciences, Case Western Reserve University, 2022, EMC - Aerospace Engineering

One of the primary stresses associated with flying high performance aircraft is acceleration, referred to as “G-force”. A critical method to combat the metabolic effects of high-G maneuvers is the Anti-G Straining Maneuver (AGSM), a respiratory technique designed to offset the effects of high-G on the human body. A dedicated and extensive flight test program is carried out to analyze the performance of legacy breathing systems during maneuvers between +3 and +5 G. A pilot mounted sensor package is utilized to obtain metabolic data during individual sorties. Data is recorded for breathing systems holding the pilot breathing mask at 100% oxygen and positive pressure (+2-3 mmHg relative to the cabin) as well as systems following a pressure dependent oxygen dilution schedule at net zero pressure. This data is utilized to characterize the effects of the AGSM on pilot breathing and identify shortcomings in the response to AGSM breathing.

Committee: Paul Barnhart (Committee Chair); Bryan Schmidt (Committee Member); Stephen Hostler (Committee Member) Subjects: Aerospace Engineering; Engineering; Fluid Dynamics; Mechanical Engineering; Physiology

Doctor of Philosophy, The Ohio State University, 2020, Biomedical Engineering

Biomechanical interaction between fluid flow and biomaterials have been assessed for different applications and have provided enhanced understanding on many biological tissues and organs. The body of this work exhibits the application of fundamental fluid mechanics for biomedical applications. In this work, we aim to utilize fluid mechanics principles to characterize the interaction between medical devices and human body in other to improve two minimally invasive medical devices for cardiovascular and ocular applications. In particular, the two systems explored in this document are that of the interaction of a blood analog with prosthetic heart valves for an improved heart valve leaflet and stent design, and the interaction of an air-puff with anterior corneal surface to estimate IOP and characterize corneal biomechanics. While the two have very different natures, the governing equations and the backbone are very much the same. The results of this work have significant effect on clinical applications of the devices. For heart valves, we have demonstrated the importance of leaflet and stent design on thrombosis and hemolysis, two major complications with heart valve replacement. With corneal tissue characterization, we have demonstrated the importance of load as a confounding variable in disease diagnosis and assessing the risk for refractive surgery.

Committee: Cynthia Roberts (Advisor); Matthew Reilly (Advisor); Jun Liu (Committee Member) Subjects: Biomechanics; Biomedical Engineering; Biomedical Research; Mechanical Engineering; Mechanics; Ophthalmology

Doctor of Philosophy (PhD), Wright State University, 2019, Engineering PhD

Drop on demand (DOD) inkjet printing has been widely investigated for its low cost, noncontact, high throughput, and reproducible process advantages. This dissertation research sought to capitalize on these advantages for use in micro solid oxide fuel cells (micro SOFCs). Understanding the important variables underpinning the inkjet process, including ink formulation, jet kinematics, and process settings was essential. These variables were evaluated for their impact on drop deposition quality, resolution, microstructure, and electrochemical functionality, with the end goal of making submicron to micron scale ceramic features. Initially, the fluid kinematics of single pass printing was investigated using a dilute, solid-solvent, colloidal, ink suspension of of La0.6Sr0.4Fe0.8Co0.2O3 (LSFC) and α-terpineol. Favorable process conditions were identified that attained uniform, well-shaped, circular dots ~ 0.1 μm thick and ~ 80 μm in diameter. Multiple, sequential ink passes were employed to increase feature dimensions on the x/y/z axes. This required additional process constraints to control deposition quality and resolution of micro features including micro-dots (0-D), micro-lines (1-D) and micro-planes (2-D). Using optimal conditions, 0-D dots and 1-D lines with x/y dimensions < 100 μm and z axis dimensions < 1 μm with dense, open or networked microstructures were demonstrated; in addition 2-D planes having smooth surface and continuous intra-planar ceramic coverage with dimensions as small as ~ 100 μm by ~ 100 μm were achieved. Sintering the inkjetted submicron prototypes produced consolidated submicron films that were uniform, smooth and void of defects such as cracks or delamination. Thermal treatments resulted in grain growth from an average crystallite size of ~158 nm to ~ 356 nm. Heat treatments < 800°C were essential to avoid deleterious effects on electrochemical activity. Electrochemical characterizations of prototypes produced tolerable peak power (open full item for complete abstract)

Committee: Hong Huang Ph.D. (Advisor); Sharmila Mukhopadhyay Ph.D. (Committee Member); Jason Deibel Ph.D. (Committee Member); Lei Kerr Ph.D. (Committee Member); Thomas Reitz Ph.D. (Committee Member) Subjects: Engineering; Materials Science

Doctor of Philosophy, Case Western Reserve University, 2019, Applied Mathematics

Conditions for bubble cavitation and behavior in non-Newtonian fluids have numerous applications in physical sciences, engineering and medicine. Non-Newtonian fluids are a rich, but relatively undeveloped area of fluid dynamics, with phenomena from di↵u- sion to bubble growth just beginning to receive attention. In the course of examining bubble cavitation, it became apparent that the random particle motion responsible for determining potential bubble formation had not been researched. As cavitation bub- bles collapse, they deform into a variety of non-spherical shapes. Due to the complex dynamics and the radial focus of current equations on bubble behavior, no accepted model has yet emerged. This work explores the behavior using numerical methods on both fluid and bubble models to examine this system from di↵erent prospectives, culminating in a time-fractional, power-law Burger's type equation showing bubble formation under these conditions.

Committee: Wojbor Woyczynski (Advisor); David Gurarie (Committee Member); Longua Zhao (Committee Member) Subjects: Applied Mathematics

Master of Science in Mechanical Engineering (MSME), Wright State University, 2019, Mechanical Engineering

The low-pressure turbine is an important component of a gas turbine engine, powering the low-pressure spool which provides the bulk of the thrust in medium- and high-bypass engines. It is also a significant fraction of the engine weight and complexity as it can comprise up to a third of the total engine weight. One way to drastically reduce the weight of the low-pressure turbine is to utilize high lift blades. To advance high-lift technology, the Air Force Research Laboratory (AFRL) designed the L2F blade profile, which was implemented in the linear cascade at AFRL/RQT's low speed wind tunnel facility. The L2F blade has very high lift and an excellent midspan performance, however, it was previously demonstrated to generate significant losses in the endwall region. These losses are primarily driven by the complex time-dependent three-dimensional vortical structures present in the region of the junction of the blade and the endwall, dominated by the Passage Vortex (PV). Aerodynamic flow control is one way to mitigate these losses. Previously, a pulsed endwall blowing system was implemented in the endwall region of the L2F blade which produced a loss reduction. This loss reduction was dependent on the pulsing frequency. In this research, the vortical structures for the baseline flow were characterized with respect to time. The time dependent behavior of the passage vortex motion, location, and strength were found for each pulsing frequency to determine a relationship with total pressure loss reduction. The flow through the passage of the tunnel was characterized with respect to time using high-speed stereoscopic particle image velocimetry. The flow for each test condition was characterized using Q-criterion to determine the strength of the passage vortex and its time dependent behavior. It was found that the passage vortex loses and gains strength in an unsteady manner at time scales between 1.9 < ΔT+ < 6.7. The largest total pressure loss reduction was found to corres (open full item for complete abstract)

Committee: Mitch Wolff Ph.D. (Advisor); Christopher R. Marks Ph.D. (Committee Member); Rolf Sondergaard Ph.D., P.E. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2018, Mechanical Engineering

Transcatheter aortic valve (TAV) replacement (TAVR) and transcatheter valve-in-valve (ViV) procedures represent less invasive solutions to some of the most important cardiac diseases such as aortic stenosis and aortic insufficiency than the conventional surgical aortic valve surgery and redo surgery for high-risk patients. However, TAVR is associated with several recurring adverse effects like residual stenosis, paravalvular leakage, coronary obstruction and reduced leaflet mobility. Much of the adverse outcomes are fundamentally related to blood flow which is pulsatile, turbulent and unsteady in nature and is further complicated by the time dependent variability of the valve orifice area. The interaction of this complex jet and its surrounding more complex geometry and anatomy leads to complicated local fluid dynamics such as shear layers, vortex formation and propagation, flow separation, flow stagnation and recirculation regions. The objective of this dissertation is to introduce new knowledge that highlights key mechanisms of how patient-specific parameters along with valve types and configurations dictate local flow behavior as well as valve function (pressure gradients, effective orifice areas etc.). The overarching hypothesis driving this research is that consideration of patient-specific parameters along with valve types and configurations significantly dictate local flow behavior as well as valve function. To test this hypothesis, state-of-the-art methods using patient-specific 3D printing, time-resolved particle image velocimetry (PIV) measurements and high-speed imaging were performed in both native, as well as TAVR configurations. Pressure gradients, effective orifice areas, shear stress, leakage or regurgitant fractions, pinwheeling indices, velocity and vorticity fields, sinus washout, Reynolds shear stresses and turbulent kinetic energy were calculated. These studies have shown that: (1) Sinus flow dynamics are highly sensitive to valve-root intera (open full item for complete abstract)

Committee: lakshmi Prasad Dasi (Advisor); Samir Ghadiali (Committee Member); Rizwan Ahmad (Committee Member); Scott Lilly (Committee Member); Theordore Chao (Committee Member) Subjects: Mechanical Engineering

Master of Science, University of Akron, 2017, Biomedical Engineering

Delivery of therapeutic fluids such as surfactant solutions into lungs is a major strategy to treat various respiratory disorders. Instilled solutions form liquid plugs in lung airways. The plugs propagate downstream in airways by inspired air or forced ventilation, continuously split at airway bifurcations to smaller daughter plugs and simultaneously lose mass from their trailing menisci, and eventually rupture. A uniform distribution of the instilled liquid in lung airways is expected to increase the treatments success. The uniformity of distribution of instilled liquid in the lungs greatly depends on the splitting of liquid plugs between daughter airways, especially in the first few generations of airways from which airways of different lobes of lungs emerge. To mechanistically understand the liquid plug splitting process, we develop a novel bioengineering approach to computationally design three-dimensional bifurcating airway models using morphometric data of human lungs, fabricate seamless physical models using additive manufacturing, and examine effects of geometry of airways, fluid properties, and flow characteristics on liquid plug splitting. We find that the orientation of bifurcating airways has a major effect on the splitting of liquid plugs between daughter airways and discuss the role of various forces including inertia, gravity, and surface tension using several dimensionless groups. This work provides a fundamental understanding toward developing delivery strategies for uniform distribution of therapeutic fluids in the lungs.

Committee: Hossein Tavana PhD (Advisor); Marnie Saunders PhD (Committee Member); Jae-Won Choi PhD (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Fluid Dynamics

Master of Science, The Ohio State University, 2017, Mechanical Engineering

Flow separation leading to stall imposes considerable performance penalties on lifting surfaces. Limitations in flight envelope and loss of control are among the chief reasons for the interest in the aeronautical research community for better understanding of this phenomenon. Modern flow control techniques explored in this work can potentially alleviate the performance penalties due to flow separation. Experiments were designed to investigate excitation of flow over an airfoil with leading edge separation at a post-stall angle of attack with nanosecond pulse dielectric barrier discharge actuators. The subject airfoil is designed with a small radius of curvature that potentially challenges the task of flow control as more centrifugal acceleration around leading is required to successfully reattach the flow. The Reynolds number based on the chord was fixed at 5·105, corresponding to a freestream flow of approximately 37 m/s. An angle of attack of 19° was used and a single plasma actuator was mounted near the leading edge of the airfoil. Fully separated flow on the suction side extended well beyond the airfoil with naturally shed vortices generated at a Strouhal number of 0.60. Excitation at very low to moderate (~1) Strouhal numbers at the leading edge generated organized coherent structures in the shear layer over the separated region with a shedding Strouhal number corresponding to that of the excitation, synchronizing the vortex shedding from leading and trailing edges. Excitation around the shedding Strouhal number promoted vortex merging while excitation at higher Strouhal numbers resulted in smaller, weaker structures that quickly developed and disintegrate over the airfoil. The primary mechanism of control is the excitation of instabilities associated with the vortices shed from leading edge. The excitation generates coherent large-scale structures that entrain high-momentum fluid into the separation region to reduce the separation and/or accelerate the flow ov (open full item for complete abstract)

Committee: Mo Samimy (Advisor); James Gregory (Committee Member); Igor Adamovich (Committee Member) Subjects: Aerospace Engineering; Experiments; Fluid Dynamics

Doctor of Philosophy, The Ohio State University, 1982, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1980, Graduate School

Committee: Not Provided (Other) Subjects: Education

Doctor of Philosophy, The Ohio State University, 1978, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1977, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1977, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1972, Graduate School

Committee: Not Provided (Other) Subjects: Engineering