Master of Science, University of Toledo, 2022, Mechanical Engineering

Inducing a high voltage (in the range of kV) between two proximate electrodes creates a spark, which is known as Corona Discharge. This discharge has the ability to induce a flow (ionic wind) in the medium with which it interacts. Such a flow is what is known as an Electrohydrodynamic flow (EHD), which has found many useful applications. One of its applications is mass-transport/pumping. Such an EHD pump offers many advantages, including high power efficiency and not requiring any mechanical moving parts to operate. Moreover, introducing water vapor into the stream of the ionic wind (i.e., between the two electrodes) allows driving water droplets into certain dielectric liquid. This in turn allows for the creation of emulsions. In order to create such emulsions, an understanding of the electrohydrodynamic (EHD) performance of the corona discharge is crucial. This can lead to better homogeneity and proper water droplet distribution, insuring higher quality and more stable emulsions. This study investigates the pumping performance of an in-house built corona discharge setup for inducing circular motion in the fluid. Silicone oils of different kinematic viscosities are used as the EHD fluid. The EHD performance/fluid characteristics are studied experimentally using particle image velocimetry (PIV) under different types of current (DC and AC). Within DC, a voltage parametric study is performed to investigate the effect of different potential drops on the flow. On the other hand, a frequency parametric study is carried out to highlight the effect of such parameters on the flow under AC conditions.

Committee: Hossein Sojoudi (Committee Chair); George Choueiri (Committee Member); Omid Amili (Committee Co-Chair) Subjects: Fluid Dynamics; Mechanical Engineering

Master of Sciences (Engineering), Case Western Reserve University, 2013, EMC - Aerospace Engineering

The knowledge of the flow fields inside of microsized ionic wind pumps has become more important as the need for smaller and more efficient heat removal devices has increased. Understanding these flow fields will help optimize the ionic wind pumps. Non-intrusive microscale particle image velocemity (PIV) utilizing a microscopic objective lens is used to obtain the flow field inside of the ionic wind pump. Voltages ranging from 1700 to 2000 V are used, as well as seeded flow rates of 1.5 and 1.84 L/min. Computational models are used to qualitatively verify the flow fields. The effects of voltage and seed flow rate are also compared. The computational and PIV flow fields are shown to be very similar. It is shown that as the voltage applied to the ionic wind pump increased, the maximum velocity inside of the ionic wind pump increased, ranging from 1.71 m/s to 3.19 m/s. The average mass flow rate inside of the device also increased as the voltage increased, ranging from .0009 g/s to .0019 g/s. It is also shown that the seed flow rate has little effect on the PIV flow field obtained.

Committee: Jaikrishnan Kadambi Dr. (Advisor); Alexis Abramson Dr. (Committee Member); Yasuhiro Kamotani Dr. (Committee Member) Subjects: Aerospace Engineering

Master of Sciences (Engineering), Case Western Reserve University, 2025, EMC - Mechanical Engineering

Particle Image Velocimetry (PIV) is a technique that allows velocity measurements of a 2D plane of a fluid flow by illuminating seeding particles in the fluid with a laser sheet. However, the use of laser is often costly, introduces complexity, and poses a challenge in near-wall measurements due to light scattering from surfaces. Particle shadow velocimetry (PSV) is a novel velocimetry technique with the potential of being a low-cost, laser-free alternative to the established PIV technique. It works by tracking shadows cast by the seeding particles on an illuminated background. Little is known about the accuracy of this technique validated against PIV. This study starts by characterization the performance of this technique, presents results from two experiments using both PIV and PSV on the same plane, and discusses its advantages and potential applications.

Committee: Bryan Schmidt (Committee Chair); Chengyu Li (Committee Member); Chirag Kharangate (Committee Member) Subjects: Aerospace Engineering; Experiments; Fluid Dynamics; Mechanical Engineering

MS, University of Cincinnati, 2024, Engineering and Applied Science: Aerospace Engineering

This study underlines the impact of the flow structures on the internal flow field through shape-transitioning ducts with global favorable pressure gradients and local adverse pressure gradients, local to the shape-transitioning geometries. Results are evaluated for convergence apropos of acquisition frequency. This thesis presents preliminary results of flow structure measurement by introducing the structures with a cylindrical bluff body in the cross flow. Structure transport through the two duct configurations studied includes the free jet of a convergent nozzle and through a shape-transitioning nozzle. Particle Image Velocimetry (PIV) was employed in data acquisition considering its substantial spatiotemporal resolution necessary. Findings show that the free jet results are characterized by high-velocity jets, detached velocity deficit region at the tailing edge of the cylinder, and strong velocity gradients due to the shear layers formed between the wake, the jets, and the ambient. On the contrary, flow through the shape transitioning or favorable pressure gradient (FPG) nozzle reflects a well-behaved flow with a low-velocity region attached to the cylinder in most cases. The outcome difference primarily stems from the velocity experienced at the cylinder in each case. An examination of convergence, considering the acquiring frequency of the flow field data, unveiled a weighty impact of acquisition frequency on the results of turbulent flow fields. The ensemble average of the results based on the mathematical computation using analytical methods in the time domain revealed an overall comparable trend in results with notable distinctions in the near wake region. Convergence dependence of results on flow essence emerged with a comparison of the running averages at a point within and outside the wake. In conclusion, it was established that a smaller subset of image pairs drawn from a universal set is ample for effectively capturing the physics of the flow (open full item for complete abstract)

Committee: Daniel Cuppoletti Ph.D. (Committee Chair); Shaaban Abdallah Ph.D. (Committee Member); Paul Orkwis Ph.D. (Committee Member) Subjects: Aerospace Materials

PhD, University of Cincinnati, 2024, Engineering and Applied Science: Aerospace Engineering

Supersonic flows have been a topic of active research due to their application in various propulsion systems such as aircraft jet engines, rocket engines and more recently rotating detonation engines. Due to the inherent complexity of supersonic jets, it is critical to develop a comprehensive understanding of various flow aspects such as acoustics and flow field development to fully define them. Supersonic jet screech is a well-known flow behavior that leads to generation of sustained flow instabilities. While a vast body of research on standard circular nozzles has been conducted exploring screech, there are several aspects of screech that are not fully understood. This research focuses on the origin, growth and propagation of screech instabilities in two types of nozzle cross-sections: rectangular and square nozzle exits. Experimental studies including acoustic tests and flow visualization studies were conducted to reveal intricate mode variations in convergent-divergent rectangular jets designed Mach 1.5. A multi-mode instability mode was discovered in the rectangular jet that consisted of simultaneous symmetric and antisymmetric oscillations propagating across all shear layers. Spatial decomposition led to the identification of the interaction between the Kelvin-Helmholtz (KH) instabilities and the flow shock cell as source of symmetric instability. Additionally, the energy decomposition into the Guided Jet Mode (G-JM), shock leakage and acoustic component was demonstrated. It was deduced that sub-optimal interactions trigger multi-mode and symmetric instabilities while antisymmetric modes while optimal interactions trigger antisymmetric modes. Twin square nozzles were studied through experimental and numerical techniques. Two different types of coupled instability modes were identified. The first was an antisymmetric mode propagating along each jet with a half period phase offset. The second was a symmetric oscillation mode that led to phase locked instabi (open full item for complete abstract)

Committee: Ephraim Gutmark Ph.D. D.Sc. (Committee Chair); Shaaban Abdallah Ph.D. (Committee Member); Paul Orkwis Ph.D. (Committee Member) Subjects: Aerospace Materials

MS, University of Cincinnati, 0, Engineering and Applied Science: Aerospace Engineering

This study underlines the impact of the flow structures on the internal flow field through shape-transitioning ducts with global favorable pressure gradients and local adverse pressure gradients, local to the shape-transitioning geometries. Results are evaluated for convergence apropos of acquisition frequency. This thesis presents preliminary results of flow structure measurement by introducing the structures with a cylindrical bluff body in the cross flow. Structure transport through the two duct configurations studied includes the free jet of a convergent nozzle and through a shape-transitioning nozzle. Particle Image Velocimetry (PIV) was employed in data acquisition considering its substantial spatiotemporal resolution necessary. Findings show that the free jet results are characterized by high-velocity jets, detached velocity deficit region at the tailing edge of the cylinder, and strong velocity gradients due to the shear layers formed between the wake, the jets, and the ambient. On the contrary, flow through the shape transitioning or favorable pressure gradient (FPG) nozzle reflects a well-behaved flow with a low-velocity region attached to the cylinder in most cases. The outcome difference primarily stems from the velocity experienced at the cylinder in each case. An examination of convergence, considering the acquiring frequency of the flow field data, unveiled a weighty impact of acquisition frequency on the results of turbulent flow fields. The ensemble average of the results based on the mathematical computation using analytical methods in the time domain revealed an overall comparable trend in results with notable distinctions in the near wake region. Convergence dependence of results on flow essence emerged with a comparison of the running averages at a point within and outside the wake. In conclusion, it was established that a smaller subset of image pairs drawn from a universal set is ample for effectively capturing the physics of the flow fiel (open full item for complete abstract)

Committee: Daniel R. Cuppoletti (Committee Chair); Shaaban Abdallah (Committee Member); Paul Orkwis (Committee Member) Subjects: Aerospace Engineering; Fluid Dynamics

Doctor of Philosophy, The Ohio State University, 2024, Mechanical Engineering

In this dissertation, a series of experiments were carried out to investigate the auto-ignition process of transient fuel jets and sprays issuing into high-temperature, environments. Novel high-speed imaging and laser diagnostic techniques were developed and applied to characterize mixing and turbulent flow conditions prior to and at the onset of ignition. In addition, this research examines the topology and dynamics of ignition kernels as they grow and transition into a stable flame. Research was carried out primarily in canonical atmospheric pressure experiments, but a new high-pressure spray test facility is developed in this work with preliminary measurements presented, demonstrating new experimental capabilities. Specific contributions of this dissertation include: (1) characterization of the transient mixing processes of variable-density atmospheric pressure jets both before and after ignition, (2) determination of the most probable mixing and turbulent flow conditions leading to local auto-ignition, (3) statistical evaluation of the dynamic growth and transport of ignition kernels, (4) construction and characterization of a novel high-pressure, high temperature spray and combustion facility, and (5) demonstration of high-speed mixture fraction measurements in non-reacting and reacting sprays at realistic thermodynamic conditions. First, a series of transient gas-phase fuel jets issuing into a high-temperature, vitiated environment at atmospheric pressure was investigated. A well-known jet-into-hot coflow configuration was utilized with the addition of a fast-acting solenoid valves to achieve pulsed fuel injection in an environment with well-defined boundary conditions. Four test conditions were studied to examine the effects of variations in jet Reynolds number, the fuel mixture composition, and coflow temperature. High-speed laser Rayleigh scattering (LRS) was performed at 10 kHz to measure the mixture fraction and temperature fields from fuel injection (open full item for complete abstract)

Committee: Jeffrey Sutton (Advisor); Seung Hyun Kim (Committee Member); Datta Gaitonde (Committee Member); Igor Adamovich (Committee Member) Subjects: Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2024, Engineering

Event-based pixel sensors asynchronously report changes in log-intensity in microsecond-order resolution. Its exceptional speed, cost effectiveness, and sparse event stream makes it an attractive imaging modality for particle tracking velocimetry. In this work, we propose a causal Kalman filter-based particle event velocimetry (KF-PEV). Using the Kalman filter model to track the events generated by the particles seeded in the flow medium, KF-PEV yields the linear least squares estimate of the particle track velocities corresponding to the flow vector field. KF-PEV processes events in a computationally efficient and streaming manner (i.e.~causal and iteratively updating). Our simulation-based benchmarking study with synthetic particle event data confirms that the proposed KF-PEV outperforms the conventional frame-based (FB) particle image/tracking velocimetry (PIV/PTV) as well as the state-of-the-art event-based (EB) particle velocimetry methods. In a real-world water tunnel event-based sensor data experiment performed on what we believe to be the widest field view ever reported, KF-PEV accurately predicted the expected flow field of the SD7003 wing, including details such as the lower velocity in the wake and the flow separation around the underside of an angled wing.

Committee: Keigo Hirakawa (Committee Chair) Subjects: Aerospace Engineering; Electrical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2022, Aerospace Engineering

Combinations of various trends in global weather point towards an increased severity and frequency of wildfires. A handful of attempts have been made in the past that try to determine retardant ground deposits and their spatial distribution resulting from aerial drops in an effort to curtail fire growth. This study takes a multipronged approach at determining retardant ground deposits and spatial distribution at various coverage levels to better achieve fire control and extinguishment. The first approach fuses the dependent parameters, (line length, width, area, and ground distribution of the retardant), with the independent parameters using statistical regression in hopes to identify the probable parameters that are complicit in affecting the ground contours and their prediction the most. While the coverage prediction for the lower coverage levels (up to 3 GPC – Gallons per 100 ft.2) is accurate to 85% for area prediction with a variability of ±15% from actual while the length prediction is only accurate 58% of the time. This value was obtained using volume bounds on the input conditions. The estimate at higher coverage levels was poor along with the retardant's spatial distribution. An alternate approach was to model the drop phenomena in a relatively controlled, scaled down environment which was performed in the University of Dayton's Low Speed Wind Tunnel (UD – LSWT) facility. A 1 mm circular jet of water emanating from the underbelly of a model fuselage was placed in varying velocity crossflow (0 < Weber number < 101) of air. Shadowgraphs were initially performed, and the jet breakup was captured at 2000 frames per second which aided in discovery of breakup location with respect to surface waves. Experiments with Background Oriented Schlieren and Particle Image Velocimetry were also planned, however, they ultimately were not successful. Historical data points to two instabilities that govern the breakup process in jets, either in crossflow or quiescent a (open full item for complete abstract)

Committee: Aaron Altman (Advisor); Markus Rumpfkeil (Committee Member); Wiebke Diestelkamp (Committee Member); Sidaard Gunasekaran (Committee Member) Subjects: Aerospace Engineering

Doctor of Nursing Practice, Mount St. Joseph University , 2021, Department of Nursing

PIV infiltration and extravasation are completely preventable. Peripheral IV's (PIV) are one of the most routine procedures required for most inpatient stays. Peripheral IV infiltrations and extravasations are a preventable complication that can occur during hospitalization. Infiltrations result when fluid leaks from a PIV catheter into the surrounding tissue. Extravasation occurs when the fluid leaking from the PIV into the surrounding tissue is a vesicant, a substance that is capable of causing blistering and burns. Nurses have the responsibility to ensure the stability of the PIV and prevent any harm to the patient and they are not always aware of the potential for destruction of tissue resulting from infiltration and/or extravasation. As detrimental a PIV complication can be in an adult, it can be even more injurious to a child. This project evaluated the implementation of elements such as hourly rounding, assessment protocols, and early recognition and treatment in the reduction of peripheral IV infiltrations and extravasations.

Committee: Kristin Clephane (Advisor) Subjects: Nursing

Master of Science in Mechanical Engineering (MSME), Wright State University, 2020, Mechanical Engineering

Flow through the turbine section of gas turbine engines is inherently unsteady due to a variety of factors, such as the relative motion of rotors and stators. In low pressure turbines, periodic wake passing has been shown to impact boundary layer separation, blade surface pressure distribution, and loss generation. The effect of periodic disturbances on the endwall flow is less understood. Endwall flow in a low-pressure turbine occurs in the boundary layer region of the flow through the blade passage where the blade attaches to the hub in the turbine. The response of an endwall vortical structure, the passage vortex, to various upstream disturbances is considered in this investigation. The passage vortex is a three-dimensional unsteady flow feature which generates aerodynamic losses as it interacts with the flow along the blade suction surface. High-speed velocimetry and numerical simulations have shown that the vortex intermittently loses coherence and varies in strength and position over time. The intermittent loss of coherence of the passage vortex is believed to be related to the leading-edge junction flow dynamics. An array of pneumatic devices was installed upstream of a linear cascade of low-pressure turbine blades to produce periodic disturbances that impact the blade leading edge region. A small disturbance and a large disturbance were created and characterized by their maximum velocity deficit and nondimensionalized solenoid valve on time using a plane of particle image velocimetry. A plane of high-speed stereoscopic particle image velocimetry data was collected inside the blade passage to examine how the disturbances impacted the vortex. Surface-mounted hot-film data was collected near the leading edge and in passage region to help relate flow behavior in both locations. The size and frequency of the disturbances had a nonlinear impact on the vortex size and strength. Fourier analysis revealed that the actuation frequency caused a harmonic response, and a (open full item for complete abstract)

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

Doctor of Nursing Practice, Mount St. Joseph University , 2020, Department of Nursing

Medical surgical nurses vary in their ability to insert and assess peripheral IVs. Literature supports general lack of education in this area. The use of a blended online learning module and live simulation has been found to increase peripheral IV insertion confidence and competence (Schuster Stahl, Murray, & Glover, 2016; Schuster, Stahl, Murray, Keleekai & Glover, 2016). Internal application of a blended curriculum model for nurses indicates improved first attempt IV insertion success. Three online modules focusing on the standards of care of peripheral IV insertion, infection prevention and documentation, as well as phlebitis assessment for IVs previously inserted were completed followed by a simulation IV competence session. Student volunteers served as the patients with a practice forearm attached to the arm for cannulation. This live interaction aided in simulating a real IV insertion and assessment experience and required the learners to interact with the patient in describing the procedure. The Peripheral Intravenous Cather Insertion Confidence Assessment (validated tool) was completed by participants (n=38) pre intervention, immediately post intervention and 30 days post intervention. A Mann-Whitney U test was completed and determined that nurses' confidence was significantly higher immediately following the intervention compared to pre intervention (p=0.003) and the increase was sustained 30 days after the intervention (p<0.001). While placing an IV in simulation, the observer measured competence by verifying 28 steps required, with a 76% success rate for all 28 steps. 24% missed one step with the majority being failure to label the dressing with date, time and initials. Nurses' self-reported first attempt peripheral IV success increased significantly from the pre intervention survey to the 30-day post intervention survey (p=0.00004). While significant, additional dissemination with hospital wide application is recommended.

Committee: Nancy Hinzman Dr (Committee Chair) Subjects: Nursing

MS, University of Cincinnati, 2019, Engineering and Applied Science: Aerospace Engineering

The main objective of this research is to characterize the swirling flow in a gas fuel injector used in gas turbine engines. The experimental investigation conducted by implementing particle image velocimetry (PIV) measurements. The effect of confinement sizes are studied, as well as different Reynolds number effect. Unconfined swirling flow showed different flow characteristics than confined typical swirling flow. Unconfined flow features stronger axial jet spreads with short and thin recirculation zones, which is indicative of thin inner shear layer (ISL). The width of the vortex breakdown bubble was about the same size of the nozzle diameter in unconfined cases. Confining the swirling flow caused the width of vortex breakdown bubble to increase to become three times of the nozzle diameter with large confinement, and twice of the nozzle diameter in both medium and small confinements. In addition, the size and shape of inner recirculation zones significantly changed with confinements. Shear layer becomes thicker due the increased width of inner recirculation zones in confined cases. The axial velocity magnitude experienced reduction with confinements, indicating weaker axial jet spread. Furthermore, confinement forced the inlet jet to penetrate radially, which can be noticed by the increase radial velocity magnitude near the exit. In addition, increasing Reynolds number in confined flow induced greater radial jet dispersion. The large confinement had the lowest axial velocity magnitude and demonstrated a unique flow filed structure. Both medium and small confinements have similar axial and radial velocity values as well as similar flow characteristics. The axial centerline plots of axial velocity showed that the length of the reverse flow region or vortex breakdown are increased with confinements. The radial velocity profile, regardless of their considerably low magnitudes, illustrated non-monotonic behavior with increasing Reynolds number in all cases particula (open full item for complete abstract)

Committee: Ephraim Gutmark Ph.D. (Committee Chair); Mark Turner Sc.D. (Committee Member); Rodrigo Villalva Gomez Ph.D. (Committee Member) Subjects: Aerospace Materials

Master of Science in Mechanical Engineering (MSME), Wright State University, 2018, Mechanical Engineering

High-lift low-pressure turbine blades produce significant losses at the junction with the endwall. The losses are caused by several complex three-dimensional vortical flow structures, which interact with the blade suction surface boundary layer. This study investigates the unsteady characteristics of these endwall flow structures on a highly loaded research profile and the adjacent endwall using surface-mounted hot-film sensors. Experiments were conducted in a low-speed linear cascade wind tunnel. The front-loaded blade profile was subjected to three different inlet conditions, consisting of two turbulence levels, and three incoming boundary layer thicknesses. Multiple surface-mounted hot-film sensors were installed throughout the passage. This thesis progressed in three stages of research. The first verified that the hot-film sensors could be used to detect flow structures in the cascade. The second used the results from installed hot-films to examine the unsteady characteristics of vortices formed near the leading edge and the propagation of the passage vortex across the passage where it interacts with a corner separation along the suction surface. Simultaneous measurements from the hot-film sensors were analyzed for frequency spectra and time lag in order to provide new insight into the endwall flow dynamics. Finally, signatures from the hot-films were linked to specific flow phenomena through concurrent flow visualization. At each stage of the investigation, results were compared to the results of a numerical simulation.

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

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

Since its inception, Particle Image Velocimetry (PIV) has been increasingly used to measure the velocity of the flow field, especially in aerospace applications. One of the major assumptions of PIV is that velocity of the flow field is same as the velocity of tracers in it. The ability of PIV to measure velocity depends upon the potential of tracers to track the flow surrounding them. Shock-Boundary Layer Interactions (SBLIs) have been studied extensively over the years using experimental and computational methods due to their importance in almost every supersonic flow. PIV has been doing a great job in analyzing SBLIs over the past few years but it has its limitations especially when there are high temporal and spatial accelerations. On the other hand, numerical simulations that better predict shock interactions have a hard time analyzing the turbulence properties of SBLIs. This implies that only by using both computational and experimental results together physics of SBLIs can be better understood. The current study was divided into two parts. First, development and validation of a post-processing code to be able to accommodate the solid particles. For this, Visual3 has been chosen because it lets a user control even smallest of its processes. Visual3 code has been modified to track particles using accurate physics within a flow. Forces acting on a particle in a flow were analyzed and compared using data obtained from Modified-Visual3 (MV3). Based on this data, dominant forces on a particle in high-speed flow are determined. Results obtained from Modified-Visual3 are compared with Melling(1997) data to validate the code. A specific case is solved mathematically to compare with Modified-Visual3 and Melling's data. A second validation was done using an example of a generalized oblique shock to understand the behavior of the particle passing through the shock. Finally, particle relaxation times for different particle specifications were calculated to understand (open full item for complete abstract)

Committee: Paul Orkwis Ph.D. (Committee Chair); Prashant Khare (Committee Member); Mark Turner Sc.D. (Committee Member) Subjects: Aerospace Materials

MS, University of Cincinnati, 2017, Engineering and Applied Science: Mechanical Engineering

Lean Premixed combustors reduce NOx emissions by burning fuel at “fuel-lean” conditions. The presence of excess air in the lean mixture reduces the combustion temperature. Since thermal NOx reduces exponentially with temperature, the reduction of temperature brings about a reduction in NOx emissions. The presence of fuel rich zones leads to the formation of prompt NOx. Uniform mixing of fuel and air reduces prompt NOx by eliminating “fuel-rich” pockets in the reaction zone. In this project, gaseous fuel is injected through eight porous tubes that are aligned parallel to the axis of an axial swirler. The axial swirler differs from other axial swirlers in that it also serves as a transition zone for the fuel-air mixture. While the downstream side of the axial swirler resembles other axial swirlers, the upstream side of the swirler has eight circular holes arranged circumferentially. The circular flow area on the upstream side of the axial swirler transitions into the trapezoidal space between the vanes of on the downstream side. The porous tubes are attached to the holes on the upstream side of the swirler. The diameter of these holes matches the inner diameter of the porous tubes. Air is passed through the porous tubes and gaseous fuel mixes with air from the outside of the porous tube. The swirler helps the flow transition from a circular cross-sectional area (porous tubes) to a trapezoidal cross-sectional area (space between adjacent vanes in an axial swirler is trapezoidal). The aerodynamics of this swirler is studied using non-reacting flow PIV. PIV measurements are done on the axial plane to study the recirculation zone and on the cross-plane to study the tangential and radial velocities. A parametric study of centerbodies is conducted using PIV to attempt to narrow down to the centerbody that prevents attachment of recirculation zone to the swirler exit. Combustion testing is conducted at different preheat temperatures (400°F, 500°F, 600°F) and at (open full item for complete abstract)

Committee: San-Mou Jeng Ph.D. (Committee Chair); Umesh Bhayaraju Ph.D. (Committee Member); Milind Jog Ph.D. (Committee Member) Subjects: Aerospace Engineering

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

This thesis utilizes time-resolved particle image velocimetry (PIV) measurements to provide a detailed statistical characterization of the kinematic properties from a set of standard non-premixed flames, which serve as benchmark test cases within the turbulent combustion community. The flames under consideration are the well-characterized DLR CH4/H2/N2 jet flames operating at two Reynolds numbers, DLR A (Re = 15,200) and DLR B (Re = 22,800), where DLR A represents a robust flame condition and DLR B represents a flame near blowout with high degrees of local flame extinction. A qualitative and quantitative comparison between DLR A and DLR B is presented to understand the effect of Reynolds number variations and local flame extinction on turbulence statistics. Detailed data processing techniques to analyze the time-resolved, 2D PIV data have been developed and presented in this work. Radial profiles of the mean and RMS fluctuations of the velocity are presented and results from DLR A agree with previous point-based measurements giving confidence in the measurements and analysis. While the DLR flames are highly utilized test cases, no published velocity data from the DLR B flames is available and thus the current measurements extend the existing data set available for modelers. Probability density functions (PDFs) of various parameters including axial and radial velocity, vorticity, strain rate are presented for both flames. In general, the PDFs for the DLR B flame are much broader than DLR A flame because of the higher Reynolds number of DLR B flame; however, the same general shape is observed across the flames indicating that the high levels of local flame extinction in DLR B does not alter the functional form of the PDFs. Quantities including the mean total strain rate, Reynolds stress and turbulent kinetic energy profiles are computed and properly normalized to show the Reynolds (number) similarity of the jet flames. The observed Reynolds similarity is surprising g (open full item for complete abstract)

Committee: Jeffrey Sutton (Advisor); Seung Hyun Kim (Committee Member) Subjects: Mechanical Engineering

Master of Science in Mechanical Engineering, Cleveland State University, 2017, Washkewicz College of Engineering

Seals are able to accurately detect minute disturbances in the ambient flow environment using their whiskers, which is attributed to the exceptional capability of their whiskers to suppress vortex-induced vibrations in the wake. To explore potential applications for designing smart flow devices, such as high-sensitivity underwater flow sensors and drag reduction components, researchers have studied how the role of some key parameters of whisker-like morphology affect the wake structure. Due to the naturally presented variation in size and curvature along the length of whiskers, it is not well understood how a real whisker changes the surrounding flow and the vortex shedding behavior. This study aims to detail the flow statistics around a real Elephant Seal whisker at low Reynolds numbers (i.e. one hundred) using particle image velocimetry in a water channel. Wake flow structures are inspected and compared between two Elephant Seal whiskers (undulating) and a California Sea Lion whisker (smooth), along with idealized whisker-like models. Undulating whiskers significantly change the mean flow properties and suppress turbulence intensities in the wake region as compared to the smooth whisker at the tested Re. The undulating whiskers are able to create a low turbulence intensity area directly behind the whiskers trailing, vproviding these whiskers with their Vortex Induced Vibration reduction properties.

Committee: Wei Zhang Ph.D. (Advisor); Mounir Ibrahim Ph.D. (Committee Member); Thijs Heus Ph.D. (Committee Member) Subjects: Biomechanics; Fluid Dynamics

Master of Science in Mechanical Engineering (MSME), Wright State University, 2016, Mechanical Engineering

Improvements in turbine design methods have resulted in the development of blade profiles with both high lift and good Reynolds lapse characteristics. An increase in aerodynamic loading of blades in the low pressure turbine section of aircraft gas turbine engines has the potential to reduce engine weight or increase power extraction. Increased blade loading means larger pressure gradients and increased secondary losses near the endwall. Prior work has emphasized the importance of reducing these losses if highly loaded blades are to be utilized. The present study analyzes the secondary flow field of the front-loaded low-pressure turbine blade designated L2F with and without blade profile contouring at the junction of the blade and endwall. The current work explores the loss production mechanisms inside the low pressure turbine cascade. Stereoscopic particle image velocimetry data, total pressure loss data and oil flow visualization are used to describe the secondary flow field. The flow is analyzed in terms of total pressure loss, vorticity, Q-Criterion, Reynolds' stresses, turbulence intensity and turbulence production. The flow description is then expanded upon using an Implicit Large Eddy Simulation of the flow field. The RANS momentum equations contain terms with static pressure derivatives. With some manipulation these equations can be rearranged to form an equation for the change in total pressure along a streamline as a function of velocity only. After simplifying for the flow field in question the equation can be interpreted as the total pressure transport along a streamline. A comparison of the total pressure transport calculated from the velocity components and the total pressure loss is presented and discussed. Peak values of total pressure transport overlap peak values of total pressure loss through and downstream of the passage suggesting that total pressure transport is a useful tool for localizing and predicting loss origins and loss development using (open full item for complete abstract)

Committee: Mitch Wolff Ph.D. (Advisor); Rolf Sondergaard Ph.D. (Committee Member); Rory Roberts Ph.D. (Committee Member) Subjects: Aerospace Engineering; Engineering

Doctor of Philosophy (PhD), Wright State University, 2016, Engineering PhD

The field of FlappingWing Micro Air Vehicles (FWMAV) has been of interest in recent years and as shown to have many aerodynamic principles unconventional to traditional aviation aerodynamics. In addition to traditional manufacturing techniques, MAVs have utilized techniques and machines that have gained significant interest and investment over the past decade, namely in additive manufacturing. This dissertation discusses the techniques used to manufacture and build a 30 gram-force (gf) model which approaches the lower limit allowed by current commercial off-the-shelf items. The vehicle utilizes a novel mechanism that minimizes traditional kinematic issues associated with four bar mechanisms for flapping wing vehicles. A kinematic reasoning for large amplitude flapping is demonstrated namely, by lowering the cycle averaged angular acceleration of the wings. The vehicle is tested for control authority and lift of the mechanism using three servo drives for wing manipulation. The study then discusses the wing design, manufacturing techniques and limitations involved with the wings for a FWMAV. A set of 17 different wings are tested for lift reaching lifts of 38 gf using the aforementioned vehicle design. The variation in wings spurs the investigation of the flow patterns generated by the flexible wings and its interactions for multiple flapping amplitudes. Phase-lock particle image velocimetry (PIV) is used to investigate the unsteady flows generated by the vehicle. A novel flow pattern is experimentally found, namely “trailing edge vortex capture” upon wing reversal for all three flapping amplitudes, alluding to a newly discovered addition to the lift enhancing effect of wake capture. This effect is believed to be a result of flexible wings and may provide lift enhancing characteristics to wake capture.

Committee: George Huang Ph.D. (Advisor); James Menart Ph.D. (Committee Member); Zifeng Yang Ph.D. (Committee Member); Richard Cobb Ph.D. (Committee Member); Michael Oppenheimer Ph.D. (Committee Member) Subjects: Mechanical Engineering