Doctor of Philosophy (PhD), Wright State University, 2013, Engineering PhD

Vortex structures and vortical formation in flapping flight are directly related to the force production. To analyze the connection between vortex structures and aerodynamic performance of flapping flight, we have developed highly efficient algorithms for large-scale flow simulations with moving and deforming bodies. To further understand the underlying mechanisms of force generation caused by the coherent structures of the vortex formation, a new analysis method has been developed to measure the influence of Proper Orthogonal Decomposition (POD) modes on aerodynamic forces. It is challenging to finish three-dimensional Direct Numerical Simulations (DNS) of insect flight in a limited amount of time. In the current work, the Modified Strongly Implicit Procedure (MSIP) has been implemented into an existing Computational Fluid Dynamics (CFD) solver, as a smoother for the multigrid method to solve the pressure equation and an iterative method to solve the momentum equation. The new solver is capable of performing a 17-million-mesh simulation within 10 days on a single core of an Intel i5-3570 chip at 3.4GHz, nearly 10 times faster than the traditional Line-SOR solver. Based on this numerical tool, the free flight of a dragonfly for eight-and-a-half wing beats is studied in detail. The results show that the dragonfly has experienced two flight stages during the flight. In a maneuver stage, wing-wake interaction generated by the fore- and hindwings attenuates the total force by 8% (peak value). In contrast, in an escape stage, the fore- and hindwings collaborate to generate force which is 8% larger than when they flap separately. Especially, the peak force on the forewing is significantly increased by 42% in a downstroke and this enhancement is known to associate with a distorted trailing edge vortex, as demonstrated by a theoretical model based on wake survey methods. The movement of the trailing edge vortex is a response to the motion of the hindwing. When the fore- (open full item for complete abstract)

Committee: Haibo Dong Ph.D. (Advisor); George Huang Ph.D. (Committee Member); Joseph Shang Ph.D. (Committee Member); Keke Chen Ph.D. (Committee Member); Aaron Altman Ph.D. (Committee Member) Subjects: Aerospace Engineering; Engineering; Fluid Dynamics

MS, University of Cincinnati, 2021, Engineering and Applied Science: Biomedical Engineering

Emergency medical services (EMS) providers have been some of the most exposed healthcare workers during the COVID-19 pandemic even when wearing personal protective equipment. Pre-hospital environments have a high risk of disease transmission exposing EMS providers to bioaerosols and droplets from infectious patients. Field intubation procedures may be performed causing the generation of bioaerosols, thereby increasing the exposure of EMS workers to pathogens. Additionally, ambulances have a reduced volume compared to a hospital treatment space, often without an air filtration system and no control mechanism to reduce exposure. The present study evaluated two different filtration concepts for reducing aerosol concentrations in the patient module of the ambulance. Concentration measurements were done in an unoccupied research ambulance at NIOSH Cincinnati using a tracer aerosol and optical particle counters. The first filtration concept evaluated small portable HEPA filter units within the ambulance compartment after the aerosol generation had occurred. The second concept was a containment pod with a HEPA-filtered evacuation system that was developed and tested based on its ability to contain, capture, and remove aerosols during the intubation procedure. The portable HEPA units reduced aerosol concentration by about 1/3rd within the initial 10 minutes of testing, when compared to the natural decay. The containment pod with HEPA-filtered evacuation showed instantaneous containment of generated particle concentrations followed by rapid air cleaning within the containment pod. Both filtration concepts can help reduce aerosol concentrations within the ambulance patient module.

Committee: Rupak Banerjee Ph.D (Committee Chair); Thomas Talavage (Committee Member); Kenneth Mead Ph.D. (Committee Member) Subjects: Biomedical Research

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

The current research investigates the spectral characteristics of combustion noise from a non-premixed methane fueled combustor. Sound pressure measurements were recorded using a near field microphone array. The noise emission was studied for different operating and geometric parameters. The operating parameters investigated in this research include the equivalence ratio and the inlet mass flow rate. The geometric parameters examined here include the flame tube confinement ratio and the swirl nozzle type. The noise spectra were always modulated by peaks. COMSOL eigen frequency analysis was used to relate the different peaks found in the experimental spectra to the corresponding acoustic eigen modes of the combustion system. The low emission air-blast type swirl nozzle produced lower noise levels compared to the pressure atomized swirl nozzle for all stable operating conditions. This research also examines the stability characteristics of the low emission nozzle for different equivalence ratios. The system exhibited thermoacoustic oscillations for higher equivalence ratios. The unstable combustion oscillations were found to couple with an eigen mode of the upstream plenum. High speed OH* imaging was done to capture the OH* fluctuations in the reaction zone for both the unstable and stable conditions. POD and DMD analysis on the flame images revealed the presence of an axial mode associated with the instability and a helical mode associated with PVC. The PVC was dominant at an equivalence ratio close to the lean blowout limit. The axisymmetric thermoacoustic mode was dominant at higher equivalence ratios. Vortex shedding was identified as the driving mechanism for the thermoacoustic instability. Adding a plate with an orifice of one nozzle diameter at the exit of the combustor pushed the onset of instability to a lower equivalence ratio.

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

Doctor of Philosophy, The Ohio State University, 2019, Aeronautical and Astronautical Engineering

Scramjet-based, air-breathing propulsion systems are poised to enable development of hypersonic defense, high speed transport, and access-to-space aerospace vehicles. A particular variant of scramjet engine, the dual-mode scramjet, is capable of operating in subsonic- and supersonic-burning modes and is attractive for flight at or above Mach 5. Despite the relative geometric simplicity of such scramjet engines, the intense hypersonic flight environment presents challenges to routine, long-duration hypersonic flight in the form of shock-turbulence interactions, heat-transfer, and turbulent-combustion. A critical component of dual-mode scramjets, the isolator, conditions the flow before it reaches the combustion zone and contains the Pre-Combustion Shock-Train (PCST) which forms in response to the pressure rise due to chemical heat release. When subjected to sufficiently large mechanically- or chemically-induced back-pressures, the isolator may unstart, resulting in the rapid ejection of the shock-train from the isolator, adversely affecting controllability and survivability of high-speed air-breathing vehicles. To better anticipate and control for isolator unstart events, detailed understanding of the combustor dynamics is required. In particular, the selection and placement of measurement sensors for ground and flight experiments is predicated on quantifying the dynamic response of the scramjet engine system. This dissertation computationally studies the isolator dynamics during a fuel-staging-induced unstart event. In this process, fuel flow rates are varied in time between two reference fueling states studied experimentally and characterized as aft-fueled and forward-fueled biased, respectively. The dynamics of a rectangular cross-section scramjet combustor, in the presence of simulated inflow-distortion, are described and quantified with respect to combustion-induced unstart. Because of the high Reynolds number and multi-physics effects of mixing (open full item for complete abstract)

Committee: Datta Gaitonde (Advisor); Jen-Ping Chen (Committee Member); Jeffrey Donbar (Committee Member); Seung Hyun Kim (Committee Member); Mo Samimy (Committee Member) Subjects: Aerospace Engineering

Master of Science, The Ohio State University, 2018, Computer Science and Engineering

High-fidelity observations of non-linear dynamical systems that are of practical interest lead to massive data sets which do not fit on a single computing node. Therefore, modal decomposition techniques must be able to exploit the capability of high-performance computing (HPC) facilities. Proper Orthogonal Decomposition and Sparse Coding are two of the commonly used modal decomposition techniques to obtain reduced order models. The goal of the research is to parallelize and implement these algorithms so that they can be used on high-performance computing clusters in order to expedite the process of modal decomposition from massive data sets. However, computation on various machines is associated with high memory usage and significant communication cost. Moreover, the overall computational cost is sensitive to the type of data set and various parameters of the algorithm. Therefore, several strategies are discussed and implementations are developed to address these constraints to perform expedient modal decomposition. Furthermore, a systematic study is performed over multiple data sets to assess the performance and scalability of the implementations.

Committee: Jack McNamara (Committee Member); Sadayappan P (Advisor) Subjects: Aerospace Engineering; Computer Science

Doctor of Philosophy (Ph.D.), University of Dayton, 2015, Mechanical Engineering

An experimental campaign was undertaken to investigate the thermo-acoustic properties of a bluff-body stabilized flame in an atmospheric pressure facility at the Air Force Research Laboratory. Of particular interest were the possible interactions between the acoustic properties of the test rig, the vortex shedding due to the presence of the bluff-body, and the unsteady heat release within the chamber. An analysis of the vortex shedding modes due to the bluff-body and the acoustic modes indicated that there are regions in the operating envelope where the two mode types share similar frequencies given an operating condition, creating a scenario where feedback might be possible. Further investigation into the fluctuating velocity components in the wake of the bluff-body indicated that the Strouhal number is not single-valued, and that vortices of varying sizes, and accompanying characteristic frequencies, are shed from a single bluff-body. With previous research indicating that lean blow-off is preceded by local extinctions within the reaction zone, and blow-off being closely related to the ratio of chemical and fluidic time scales, an experiment was conducted to determine whether or not flames undergoing thermo-acoustic instability also exhibit regions of decreased residence time. This experiment concluded that the regions of acoustically-coupled flames which undergo large-scale oscillations do, in fact, correlate with decreased residence time. This conclusion links both lean static stability and near-stoichiometric dynamic stability to simple time scales prescribed by vortex behavior in the wake of a bluff-body. An investigation was conducted which utilized simultaneous high-speed particle image velocimetry (PIV), planar laser-induced fluorescence (PLIF) and pressure measurements in the near-wake region of a bluff-body stabilized flame. In addition to the simultaneous measurements listed, high-speed broadband chemiluminescence was also collected. The 2-D (open full item for complete abstract)

Committee: Ahmad Kashani Ph.D. (Committee Chair); Scott Stouffer Ph.D. (Committee Member); Vincent Belovich Ph.D. (Committee Member); Kevin Hallinan Ph.D. (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2015, Engineering and Applied Science: Aerospace Engineering

In recent times, there have been a growing number of aerospace application utilizing “Intelligent Systems” methods. These methods include Genetic Algorithms and Fuzzy Logic. Genetic Algorithms were used as an optimization tool for morphing wing airfoils and to optimize Fuzzy Logic path planning algorithms. Fuzzy Logic was used to guide an agent through a hazard field while minimizing exposure to the hazard. Additionally, advanced statistical techniques such as Proper Orthogonal Decomposition were used in the investigation of creating low-order models of supersonic cavity flows, and attempting to remove noise (such as smoke) from video taken during fire-fighting operations. The main goal of this research was take these intelligent systems methods and utilize them to develop user-friendly software applications which can be used by undergraduate and graduate students. It is for this reason that the source code is being included in this thesis, to allow future students to utilize and build upon these applications. AeroMorph provides the user with a graphical interface which can be used to optimize airfoils shapes for a given flight scenario. It uses XFOIL as a virtual wind tunnel to provide quick results which are then optimized using the genetic algorithm. Then the optimized airfoil can be tested against the original to see the improvement. GAPPER provides graphical tools to build hazard maps and solve them using different Fuzzy Logic path-planning routines. The user can use a genetic algorithm to optimize a path-planning routine and then the user can directly control the agent to benchmark the path-planning routine against a human. ssPOD provides a graphical environment in which Proper Orthogonal Decomposition can be performed on a variety of different problems. It quickly and efficiently provides results for a number of useful variables, and includes plotting tools to make communication of results easy. The MATLAB programs were benchmarked to determine (open full item for complete abstract)

Committee: Kelly Cohen Ph.D. (Committee Chair); Shaaban Abdallah Ph.D. (Committee Member); Awatef Hamed Ph.D. (Committee Member); Manish Kumar Ph.D. (Committee Member) Subjects: Aerospace Materials

Doctor of Philosophy (PhD), Wright State University, 2014, Engineering PhD

The reliability of Nondestructive Evaluation (NDE) is an important input for risk analysis for sustainment of aging infrastructure. Reliability has typically been quantified via probability of detection (POD) studies. There are three problems with POD modeling methodologies provided in the most recent guidance on the subject: 1) Current models do not estimate the extremes of a POD curve very well because of the assumption that the POD curve approaches zero as flaw size goes to zero, and the POD curve approaches one as the flaw size goes to infinity. 2) The existing 2-parameter logit/probit models can be misused since there is not a set of diagnostics and procedures that can catch every violation of fundamental assumptions. 3) Data sets from realistic inspections often violate core assumptions in statistical models such as homoscedasticty and linearity, but statistical inference is still needed for the application. Since one of the important inputs to risk assessment is POD, and it's believed that the output of risk analyses can be sensitive to the tail behavior at large flaw sizes, it is worthwhile to consider better estimation procedures for the extremes of a POD curve. In this dissertation, new POD models that include lower and upper asymptotes are proposed to better model tail behavior. Transformations such as Box-Cox are proposed to mitigate violations of homoscedasticity, and bootstrapping is proposed to provide confidence bound calculations for higher order models. A case study is presented where these improvements to POD analysis are incorporated into a risk analysis. Simulation studies a presented to quantify the improvements of this work.

Committee: Ramana Grandhi Ph.D. (Advisor); Frank Ciarallo Ph.D. (Advisor); Michael Grimaila Ph.D. (Committee Member); Yan Liu Ph.D. (Committee Member); Pratik Parikh Ph.D. (Committee Member); Xinhui Zhang Ph.D. (Committee Member) Subjects: Engineering

MS, University of Cincinnati, 2011, Engineering and Applied Science: Aerospace Engineering

The well known criterion for combustion instability is called the Rayleigh's criterion. It indicates that, for combustion instability to occur, the heat release rate (q') and pressure oscillation (p') must be in phase. This thesis describes measurement techniques and study methods for combustion instabilities that occurred in the prototype single annular sector Rich-Burn Quick-Mix Lean-Burn (RQL) combustor on the original (short) and new (long) experimental rig configuration with a focus on q' and p' measurements. A change in the configuration of the combustor rig was necessary in order to acquire more precise measurements of forward- and backward-moving acoustic pressure waves within the rig by mounting pressure transducers on preselected locations of the upstream duct, downstream duct and combustion area. Pressure transducers provided such local pressure behaviors as amplitude and frequency per location, also in addition to transfer functions that allow for the calculation of the acoustic impedance at any location within the combustor rig. A high-speed camera was capable of filming a chemiluminescene image, i.e., the rate of heat release through a quartz window that is mounted on the side of the combustor. Two imaging analysis techniques, Proper Orthogonal Decomposition and Fourier Transformation, were applied to the chemiluminescene image obtained by a high-speed video device. Two different test cases were investigated. Both a high and low fuel-to-air ratio were used for the investigation of the Rayleigh's criterion, which was confirmed by the corresponding q' and p' data sets. Finally, the resonance frequency that agrees with combustion instability was well predicted by utilizing the one-dimensional wave propagation theory and the known geometry of the combustor rig, temperature of fluid, and boundary conditions.

Committee: San-Mou Jeng PhD (Committee Chair); Shanwu Wang PhD (Committee Member); Kelly Cohen PhD (Committee Member); Asif Syed PhD (Committee Member) Subjects: Aerospace Materials

Master of Science, The Ohio State University, 2012, Human Ecology: Human Nutrition

Body composition estimates are used in clinical and research settings. Accurate estimates of percent body fat, lean mass and bone density are desirable to many clients and researchers in health-related fields. Two current methods considered accurate and reliable are the BOD POD and iDXA. Studies comparing the accuracy of these two methods have shown that there is a statistically significant difference of 1-3% in the percent body fat in populations studied, and this difference can be easily attributed to either method. The purpose of this case-control study is to evaluate how bone density may influence the difference for body fat estimates between the BOD POD and the iDXA machines when comparing bone adequate versus osteopenic female runners from a parent study which included 125 recreational female runners. Cases were invited to participate in this BOD POD study based on low bone mineral results (Z score < -1.0 for total body or lumbar spine). Bone adequate controls were at least average or better (Z score > 0). Cases and controls were matched on age (within + 3 years), body size using body height (within + three inches) and weight (within + ten pounds). After each case, an appropriate control (Z-score > 1.0 for total body or lumbar spine) was identified and invited to participate yielding a total of 15 pairs of subjects. Analysis of the percent body fat between the BOD POD and iDXA for each subject was performed by evaluating the calculated difference between the measures, and the data compared between the Case-Control groups. The group variances were determined similar using the Folded F statistic (p = 0.7366). Paired T-test analysis between groups demonstrated no significant difference (p = 0.1102) in the difference variable between the cases (mean 0.68 +1.51) and controls (mean 1.63 +1.66). Power analysis was performed using the mean and standard deviations of the actual sample (1) and indicated a low powered study (1-β = 0.24), and it would have required 77 sub (open full item for complete abstract)

Committee: Jackie Buell PhD, RD, LD (Advisor); Joshua Bomser PhD (Committee Member); Diane Habash PhD (Committee Member) Subjects: Anatomy and Physiology; Biology; Food Science; Health; Health Care; Health Education; Health Sciences; Nutrition; Physical Education; Public Health; Rehabilitation; Sports Medicine

Doctor of Philosophy, The Ohio State University, 2008, Mechanical Engineering

Controlling the flow over aerodynamic bodies has been a challenging problem for many years. Different open loop control techniques have been used in several flow configurations with some degree of success. However, in most cases the effectiveness of the controller is limited to the design conditions. In the present work, Proper Orthogonal Decomposition (POD) is used to derive low dimensional models of the subsonic flow over a cavity, in an effort to develop a feedback control system that can control the characteristic of the flow field. The Galerkin method is used as an additional tool to capture the time evolution of the flow field, reducing the problem into a system of ordinary differential. The stochastic estimation method is then used to link the variables that can be physically measured with those involved in the model. Particle Image Velocimetry (PIV) data and surface pressure measurement for the unforced flow (baseline) and for several open loop forcing conditions are used to derive the models. Three different approaches are investigated for control input separation. Different combinations of the flow condition are used in the model derivation to determine which forced flow should be used as a general case. A feedback controller is designed and tested experimentally for each model. The results showed that the variation in the experimental SPL spectra between the different models was negligible. However, a closer look at other factors hinted that the actuation mode separation method (M1) using the white noise forcing is the best choice. This method of separation does not require a clear identification of the control input region in the data. Also, it generates the best results in terms of reducing the tone and the OASPL while using a lower power input to achieve it. The white noise forcing helps to simplify the derivation process, as there is no need to pre-identify a specific forcing case. The multiple time estimation provides the best results in terms of the (open full item for complete abstract)

Committee: Mo Samimy Dr. (Advisor); Michael Dunn Dr. (Committee Member); Chiu-Yen Kao Dr. (Committee Member); Walter Lempert Dr. (Committee Member); Andrea Serrani Dr. (Committee Member) Subjects: Aerospace Materials; Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2007, Electrical Engineering

Flow control refers to the ability to manipulate fluid flow so as to achieve a desired change in its behavior, which offers many potential technological benefits, such as reducing fuel costs for vehicles and improving effectiveness of industrial processes. An interesting case of flow control is cavity flow control, which has been the motivation of this study: When air flow passes over a shallow cavity a strong resonance is produced by a natural feedback mechanism, scattering acoustic waves that propagate upstream and reach the shear layer, and developing flow structures. These cause many practical problems including damage and fatigue in landing gears and weapons bays in aircrafts. Presently there is a lack of sufficient mathematical analysis and control design tools for flow control problems. This includes mathematical models that are amenable to control design. Recently reduced-order modeling techniques, such as those based on proper orthogonal decomposition (POD) and Galerkin projection (GP), have come to interest. However, a main issue with these models is that the effect of boundary conditions, which is where the control input is, gets embedded into system coefficients. This results in a form quite different from what one deals with in standard control systems framework, which is a set of ordinary differential equations (ODE) where the input appears as an explicit term. Another issue with the standard POD/GP models is that they do not yield to systems that have any apparent structure in their coefficients. This leaves one with little choice other than to neglect the nonlinearities of the models and employ standard linear control theory based designs. The research presented in this thesis makes an effort at closing the gaps mentioned above by 1) presenting a reduced-order modeling method utilizing a novel technique for input separation on POD/GP models, 2) introducing a technique based on averaging theory and center manifold theory so as to reveal certain struct (open full item for complete abstract)

Committee: Andrea Serrani (Advisor) Subjects:

Master of Science (MS), Ohio University, 2004, Nutrition Science (Health and Human Services)

This study aimed at exploring the attitudes toward obesity and its association with dietary intake and percent body fat between dietetic and non-dietetic majors. Sample comprised of 76 dietetic and non-dietetic majors from Ohio University who were 18 years or older and females. Attitudes toward the obesity were determined using 14-item Fat Phobia Scale. Dietary intake was measured using Block 98 Food Frequency Questionnaire. Percent body fat was measured using Bod Pod. Results suggest that both groups were similar on their percent body fat and overall level of fat phobia. However, there were intriguing, but subtle differences in dietary intake and in the rating of adjectives comprising the fat phobia scale between the groups. Overall, both groups had similar macronutrient intake. The only significant differences between groups were in percent fat (17 grams) and grams of fat (5grams) consumed. Dietetic majors demonstrated a slightly healthier macronutrient and food group intake pattern as compared to the non-dietetic majors.

Committee: Darlene Berryman (Advisor) Subjects:

Master of Education (MEd), Bowling Green State University, 2007, Human Movement, Sport and Leisure Studies /Kinesiology

The primary purpose of this investigation was to compare percent body fat (%BF) determined using skinfold regression equations for female athletes to %BF measured using the BOD POD (Life Measurement, Inc., Concord, CA) as the criterion measure. Valid skinfold equations for female collegiate athletes allow individuals to accurately and easily determine players' %BF in a field setting. The accurate determination of body fat in female athletes enables pre- and post-season assessments as well as allows for potential diagnoses of symptoms involved in the female athlete triad (Fornetti et al., 1999; Nattiv & Lynch, 1994; Warner et al., 2004). The BOD POD has been shown to be a valid source of measurement of body composition in female athletes when compared to underwater (hydrostatic) weighing (UWW) and dual-energy x-ray absorptiometry (DEXA). Participants in this study were 75 female collegiate athletes at a Division III University between the ages of 18-24 years. Each participant was tested in the BOD POD and had four skinfold sites measured. Criterion-related concurrent validity and intraclass reliability were tested before testing began to ensure the investigator was valid and reliable at taking skinfold measurements. Three previously developed skinfold equations for females were used to calculate %BF: The first equation (SF-UWW) utilized UWW as the criterion, the second equation (SF-DEXA) was developed using DEXA as the criterion, while the third equation (SF-Gen) was a general skinfold equation that has been recommended for women ages 18-55 years using UWW as the criterion. A one–way analysis of variance (ANOVA) was performed with repeated measures on the four body composition techniques. Tukey's HSD post hoc analysis was used to compare the means for each technique. Cohen's d was used to calculate effect size for mean differences. No significant differences were found between the BOD POD and any of the skinfold measurements. However, significant differences were fou (open full item for complete abstract)

Committee: Amy Morgan (Advisor); Lynn Darby (Committee Member); David Tobar (Committee Member) Subjects: