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Title: convective heat transfer in quasi-one-dimensional magnetic fluid in horizontal field and temperature gradients.
Creator: Huang, Jun, Luo, Weili, Schulte, Alfons, Del Barco, Enrique, Kassab, Alain, University of Central Florida
Abstract / Description: In this work we studied the convective heat transfer in a magnetic fluid in both zero and applied magnetic fields. The natural convection is observed in a quasi-one dimensional magnetic fluid in a horizontal temperature gradient. The horizontal non-homogeneous magnetic fields were applied across the sample cell either parallel or anti-parallel to the temperature gradient. The temperature profile was measured by eight thermocouples and temperature sensitive paint. The flow velocity field and...
Show moreIn this work we studied the convective heat transfer in a magnetic fluid in both zero and applied magnetic fields. The natural convection is observed in a quasi-one dimensional magnetic fluid in a horizontal temperature gradient. The horizontal non-homogeneous magnetic fields were applied across the sample cell either parallel or anti-parallel to the temperature gradient. The temperature profile was measured by eight thermocouples and temperature sensitive paint. The flow velocity field and streamlines were obtained by optical flow method. Calculated Nusselt numbers, Rayleigh number, and Grashof number show that the convective flow is the main heat transfer mechanism in applied fields in our geometry. It was found that when the field gradient is parallel with temperature gradient, the fields enhance the convective heat transfer while the fields inhibit it in anti-parallel configuration by analyzing the temperature difference across the sample, flow patterns, and perturbation Q field in applied fields. Magnetic Rayleigh number and magnetic Grashof number show that the thermomagnetic convections dominate in high magnetic fields. It is shown that the physical nature of the field effect is corresponding to the magnetic body force which is perpendicular to the gravity in our experiments. When the direction of the magnetic body force is same with temperature gradient in parallel configuration, the body force increases the convective heat transfer; while it has opposite effect in anti-parallel configuration.Our study will not only shed light on the fundamental mechanisms for thermomagnetic convection but also help to develop the potential field-controlled heat transfer devices.
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Date Issued: 2015
Identifier: CFE0005957, ucf:50810
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005957

Title: Inverse-Consistent Determination of Young's Modulus of Human Lung.
Creator: Seyfi Noferest, Behnaz, Ilegbusi, Olusegun, Santhanam, Anand, Kassab, Alain, Moslehy, Faissal, University of Central Florida
Abstract / Description: Human lung undergoes respiration-induced deformation due to sequential inhalation and exhalation. Accurate determination of lung deformation is crucial for tumor localization and targeted radiotherapy in patients with lung cancer. Numerical modeling of human lung dynamics based on underlying physics and physiology enables simulation and virtual visualization of lung deformation. Dynamical modeling is numerically complicated by the lack of information on lung elastic behavior, structural...
Show moreHuman lung undergoes respiration-induced deformation due to sequential inhalation and exhalation. Accurate determination of lung deformation is crucial for tumor localization and targeted radiotherapy in patients with lung cancer. Numerical modeling of human lung dynamics based on underlying physics and physiology enables simulation and virtual visualization of lung deformation. Dynamical modeling is numerically complicated by the lack of information on lung elastic behavior, structural heterogeneity as well as boundary constrains. This study integrates physics-based modeling and image-based data acquisition to develop the patient-specific biomechanical model and consequently establish the first consistent Young's modulus (YM) of human lung. This dissertation has four major components: (i) develop biomechanical model for computation of the flow and deformation characteristics that can utilize subject-specific, spatially-dependent lung material property; (ii) develop a fusion algorithm to integrate deformation results from a deformable image registration (DIR) and physics-based modeling using the theory of Tikhonov regularization; (iii) utilize fusion algorithm to establish unique and consistent patient specific Young's modulus and; (iv) validate biomechanical model utilizing established patient-specific elastic property with imaging dataThe simulation is performed on three dimensional lung geometry reconstructed from four-dimensional computed tomography (4DCT) dataset of human subjects. The heterogeneous Young's modulus is estimated from a linear elastic deformation model with the same lung geometry and 4D lung DIR. The biomechanical model adequately predicts the spatio-temporal lung deformation, consistent with data obtained from imaging. The accuracy of the numerical solution is enhanced through fusion with the imaging data beyond the classical comparison of the two sets of data. Finally, the fused displacement results are used to establish unique and consistent patient-specific elastic property of the lung.
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Date Issued: 2015
Identifier: CFE0006391, ucf:51512
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006391

Title: Shock Tube and Mid-infrared Laser Absorption Measurements of Ignition Delay Times and Species Time-histories.
Creator: Koroglu, Batikan, Vasu Sumathi, Subith, Kapat, Jayanta, Kassab, Alain, Peale, Robert, University of Central Florida
Abstract / Description: Energy consumption has increased dramatically as the world advances and becomes more industrialized. Over the next twenty five years, the U.S. Department of Energy expects the energy demand to increase by 29% with majority of the new energy coming from natural gas (methane). Another promising fuel source for power generation and transportation is the biofuels. The biofuel use in the US is shown to have increased substantially in the last decade. There are serious environmental concerns...
Show moreEnergy consumption has increased dramatically as the world advances and becomes more industrialized. Over the next twenty five years, the U.S. Department of Energy expects the energy demand to increase by 29% with majority of the new energy coming from natural gas (methane). Another promising fuel source for power generation and transportation is the biofuels. The biofuel use in the US is shown to have increased substantially in the last decade. There are serious environmental concerns associated with greenhouse (e.g. carbon-dioxide) and toxic gas emissions (e.g. nitrogen oxides and aldehydes such as propanal) due to deriving energy from natural gas and biofuel combustion. In this doctoral study, a shock tube experimental setup was designed, assembled, and tested in order to study the ignition as well as thermal decomposition characteristics of two types of fuels: methane (the major natural gas component, which is also a major intermediate during higher order hydrocarbon ignition and pyrolysis) and propanal (an oxygenated hydrocarbon found in the exhaust emissions of biofuels). A laser diagnostics using semi-conductor type laser diodes in the infrared region for measurements of methane and propanal gas concentrations was developed and used with the shock tube. This diagnostics also enabled the interference-free detection of methane during the course of propanal pyrolysis. The experimental measurements highlighted the areas in which refinement of reaction kinetic models was required. The current research provided information on the ignition delay times as well as concentration time-histories of fuels (e.g. propanal or methane) and intermediates (e.g. methane). The knowledge gained during this doctoral study is vital for the accurate modeling of emissions due to combustion of fuels. The dissertation discusses the details of the four following items: 1) design, assembly, and testing of a shock tube setup as well as a laser diagnostics apparatus for studying ignition characteristics of fuels and associated reaction rates, 2) measurements of methane and propanal infrared spectra at room and high temperatures using a Fourier Transformed Infrared Spectrometer (FTIR) and a shock tube , 3) measurements of ignition delay times and reaction rates during propanal thermal decomposition and ignition, and 4) investigation of ignition characteristics of methane during its combustion in carbon-dioxide diluted bath gas. The main benefit and application of this work is the experimental data which can be used in future studies to constrain reaction mechanism development.
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Date Issued: 2016
Identifier: CFE0006533, ucf:51382
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006533

Title: Catalytically Enhanced Heterogeneous Combustion of methane.
Creator: Terracciano, Anthony, Orlovskaya, Nina, Vasu Sumathi, Subith, Chow, Louis, Kassab, Alain, University of Central Florida
Abstract / Description: Heterogeneous combustion is an advanced internal combustion technique, which enables heat recuperation within the flame by utilizing a highly porous ceramic media as a regenerator. Heat released within the gas phase convectively transfers to the solid media. This heat within the solid media then travels towards the inlet, enabling reactant preheating. Such heat redistribution enables stable burning of both ultra-lean fuel/air mixtures, forming a more diffuse flame through the combustion...
Show moreHeterogeneous combustion is an advanced internal combustion technique, which enables heat recuperation within the flame by utilizing a highly porous ceramic media as a regenerator. Heat released within the gas phase convectively transfers to the solid media. This heat within the solid media then travels towards the inlet, enabling reactant preheating. Such heat redistribution enables stable burning of both ultra-lean fuel/air mixtures, forming a more diffuse flame through the combustion chamber, and results in reduced pollutant formation. To further enhance heterogeneous combustion, the ceramic media can be coated with catalytically active materials, which facilitates surface based chemical reactions that could occur in parallel with gas phase reactions.Within this work, a flow stabilized heterogeneous combustor was designed and developed consisting of a reactant delivery nozzle, combustion chamber, and external instrumentation. The reactant delivery nozzle enables the combustor to operate on mixtures of air, liquid fuel, and gaseous fuel. Although this combustor has high fuel flexibility, only gaseous methane was used within the presented experiments. Within the reactant delivery nozzle, reactants flow through a tube mixer, and a homogeneous gaseous mixture is delivered to the combustion chamber. ?-alumina (?-Al2O3), magnesia stabilized zirconia (MgO-ZrO2), or silicon carbide (SiC) was used as the material for the porous media. Measurement techniques which were incorporated in the combustor include an array of axially mounted thermocouples, an external microphone, an external CCD camera, and a gas chromatograph with thermal conductivity detector which enable temperature measurements, acoustic spectroscopy, characterization of thermal radiative emissions, and composition analysis of exhaust gasses, respectively. Before evaluation of the various solid media in the combustion chamber the substrates and catalysts were characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy and energy dispersive spectroscopy. MgO-ZrO2 porous media was found to outperform both ?-Al2O3 and SiC matrices, as it was established that higher temperatures for a given equivalence ratio were achieved when the flame was contained within a MgO-ZrO2 matrix. This was explained by the presence of oxygen vacancies within the MgO doped ZrO2 fluorite lattice which facilitated catalytic reactions. Several catalyst compositions were evaluated to promote combustion within a MgO-ZrO2 matrix even further.Catalysts such as: Pd enhanced WC, ZrB2, Ce0.80Gd0.20O1.90, LaCoO3, La0.80Ca0.20CoO3, La0.75Sr0.25Fe0.95Ru0.05O3, and La0.75Sr0.25Cr0.95Ru0.05O3; were evaluated under lean fuel/air mixtures. LaCoO3 outperformed all other catalysts, by enabling the highest temperatures within the combustion chamber, followed by Ce0.80Gd0.20O1.90. Both LaCoO3 and Ce0.80Gd0.20O1.90 enabled a flame to exist at ?=0.45(&)#177;0.02, however LaCoO3 caused the flame to be much more stable. Furthermore, it was discovered that the coating of MgO-ZrO2 with LaCoO3 significantly enhanced the total emissive power of the combustion chamber. In this work as acoustic spectroscopy was used to characterize heterogeneous combustion for the first time. It was found that there is a dependence of acoustic emission n the equivalence ratio and flame position regardless of media and catalyst combination. It was also found that when different catalysts were used, the acoustic tones produced during combustion at fixed reactant flow rates were distinct
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Date Issued: 2016
Identifier: CFE0006508, ucf:51364
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006508

Title: Large Eddy Simulations with a Tabulated Conditional Moment Closure Moment Closure Model for Turbulent Premixed Combustion with Heat Loss.
Creator: Velez, Carlos, Vasu Sumathi, Subith, Martin, Scott, Kassab, Alain, Das, Tuhin, University of Central Florida
Abstract / Description: The Tabulated Premixed Conditional Moment Closure (T-PCMC) method has been shown to provide the capability to predict turbulent, premixed methane flames with detailed chemistry and reasonable run times in a RANS/URANS adiabatic environment. Here the premixed T-PCMC method is extended in a Large Eddy Simulation (LES) framework for non-adiabatic premixed flames, allowing heat loss to occur in the mixture before, during and after combustion. It is proposed that the LES framework is a more...
Show moreThe Tabulated Premixed Conditional Moment Closure (T-PCMC) method has been shown to provide the capability to predict turbulent, premixed methane flames with detailed chemistry and reasonable run times in a RANS/URANS adiabatic environment. Here the premixed T-PCMC method is extended in a Large Eddy Simulation (LES) framework for non-adiabatic premixed flames, allowing heat loss to occur in the mixture before, during and after combustion. It is proposed that the LES framework is a more suitable representation for both chemical and turbulent scales in premixed combustion. By resolving the high energy turbulent scales and modeling the small scale turbulence, it is expected that the resolution of the turbulence and transient effects are better captured in a LES framework leading to better predictions of the mixing rate and consequently the reaction rate, which is the main focus and source of error in combustion modeling. The LES T-PCMC model is implemented using the open source CFD software OpenFOAM for its open access to C++ source code and large library of turbulence and thermo-physical models. The proposed model validated with PIV and Raman measurements of a turbulent, enclosed reacting flame of a single jet and backward facing step geometry. The DLR data sets provide both unity (E.g.Methane) and non-unity (E.g. Hydrogen) Lewis number fuels, allowing for the proposed numerical model to be validated against both unity and non-unity Lewis # flames. Velocity, temperature and major/minor species are compared to the experimental data. Once validated, this model is intended to be useful for designing lean premixed combustors for gas turbines which operate primarily in the corrugated premixed combustion regime, where chemical and turbulent time scales are of the same order requiring adequate models for their interaction.LES results match the experimental data better than the Reynolds Averaged Navier-Stokes (RANS/URANS) solution and is able to better resolve the transient features of the flame with an increase in run time of only 50 %, when compared to URANS.
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Date Issued: 2015
Identifier: CFE0006234, ucf:51058
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006234

Title: Study On Anisotropic Plasticity And Fracture Of Lightweight Metal Sheets.
Creator: Jia, Yueqian, Bai, Yuanli, Kassab, Alain, Raghavan, Seetha, Gou, Jihua, Wu, Thomas, University of Central Florida
Abstract / Description: How to reduce weight and increase fuel efficiency is a critical challenge in transportation industries. One way to resolve the problem is to adopting lightweight alloys (i.e. advanced high strength steel, aluminum alloys, or magnesium alloy) in structure designs and manufacturing. Fully understanding the mechanical properties of these materials is a key step.In order to fully characterize the plasticity and fracture of magnesium AZ31B-H24 sheets, a set of mechanical experiments (170 in total)...
Show moreHow to reduce weight and increase fuel efficiency is a critical challenge in transportation industries. One way to resolve the problem is to adopting lightweight alloys (i.e. advanced high strength steel, aluminum alloys, or magnesium alloy) in structure designs and manufacturing. Fully understanding the mechanical properties of these materials is a key step.In order to fully characterize the plasticity and fracture of magnesium AZ31B-H24 sheets, a set of mechanical experiments (170 in total) were performed under both monotonic and non-proportional loading conditions, including monotonic uniaxial tension, notch tension, in-plane uniaxial compression, wide compression (or called biaxial compression), plane strain compression, through-thickness compression, in-plane shear, punch test, uniaxial compression-tension reverse loading, and two-step uniaxial tension (cross-loading).Both the plastic strain histories and stress responses were obtained under the above loading conditions, which give a comprehensive picture of mechanical behaviors of this material. No apparent cross-hardening effect was observed for this material.An extended orthotropic yield criterion involving two linear anisotropic transformation tensors, CPB06ex2, in conjunction with its associated flow rule was fully calibrated to describe both the anisotropy in plastic flow and tension-compression asymmetry in stress-strain behaviors.A fully modularized framework to combine isotropic, kinematic, and cross hardening behaviors was established under non-monotonic loading conditions. Three sets of state variables were defined and applied to consider the effects of, a) loading history, b) twinning and de-twinning and c) different pre-strain.In order to predict ductile fracture of metal sheets, the (")mixed(") stress/strain invariants based Modified-Mohr-Coulomb (MMC) fracture model was transferred into an all-strain based MMC (eMMC) model under plane stress condition, predicting the fracture strain dependent on strain ratio or ? angle, instead of stress triaxiality and Lode angle parameter. The strain ratio or ? angle could be directly measured by digital image correlation (DIC), while the latter required finite element analysis to be determined. This method makes it possible to study material fracture behavior while bypassing plasticity. The eMMC fracture locus can be fully calibrated by fracture strains directly measured from DIC. The fracture strain was also extended by a linear transformation operating to the plastic strain tensor to incorporate the fracture anisotropy. All models were implemented into Abaqus/Explicit as a user material subroutine (VUMAT). Good prediction capability has been demonstrated for magnesium AZ31B-H24 sheets by FE simulation using shell elements.The current framework was also applied for TRIP780, BH240, DP600, and EDDQ steel sheets with adjustment, under different loading conditions. The FE simulation results for TRIP780 correlated well with experimental data under different monotonic loading conditions. The analytical results for BH240, DP600, and EDDQ demonstrated good prediction capability for cross-hardening behavior, and validated by the non-proportional experimental data under two-stage uniaxial tension.
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Date Issued: 2016
Identifier: CFE0006121, ucf:51165
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006121

Title: Analytical solutions to nonlinear differential equations arising in physical problems.
Creator: Baxter, Mathew, Vajravelu, Kuppalapalle, Li, Xin, Mohapatra, Ram, Shuai, Zhisheng, Kassab, Alain, University of Central Florida
Abstract / Description: Nonlinear partial differential equations are difficult to solve, with many of the approximate solutions in the literature being numerical in nature. In this work, we apply the Homotopy Analysis Method to give approximate analytical solutions to nonlinear ordinary and partial differential equations. The main goal is to apply different linear operators, which can be chosen, to solve nonlinear problems. In the first three chapters, we study ordinary differential equations (ODEs) with one or two...
Show moreNonlinear partial differential equations are difficult to solve, with many of the approximate solutions in the literature being numerical in nature. In this work, we apply the Homotopy Analysis Method to give approximate analytical solutions to nonlinear ordinary and partial differential equations. The main goal is to apply different linear operators, which can be chosen, to solve nonlinear problems. In the first three chapters, we study ordinary differential equations (ODEs) with one or two linear operators. As we progress, we apply the method to partial differential equations (PDEs) and use several linear operators. The results are all purely analytical, meaning these are approximate solutions that we can evaluate at points and take their derivatives.Another main focus is error analysis, where we test how good our approximations are. The method will always produce approximations, but we use residual errors on the domain of the problem to find a measure of error.In the last two chapters, we apply similarity transforms to PDEs to transform them into ODEs. We then use the Homotopy Analysis Method on one, but are able to find exact solutions to both equations.
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Date Issued: 2014
Identifier: CFE0005303, ucf:50527
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005303

Title: Treatment-Specific Approaches for Analysis and Control of Left Ventricular Assist Devices.
Creator: Farag Allah, George, Simaan, Marwan, Qu, Zhihua, Haralambous, Michael, Kassab, Alain, Divo, Eduardo, University of Central Florida
Abstract / Description: A Left Ventricular Assist Device (LVAD) is a mechanical pump that helps patients with heart failure conditions. This rotary pump works in parallel to the ailing heart and provides an alternative path for blood flow from the weak left ventricle to the aorta. The LVAD is controlled by the power supplied to the pump motor. An increase in the pump motor power increases the pump speed and the pump flow. The LVAD is typically controlled at a fixed setting of pump power. This basically means that...
Show moreA Left Ventricular Assist Device (LVAD) is a mechanical pump that helps patients with heart failure conditions. This rotary pump works in parallel to the ailing heart and provides an alternative path for blood flow from the weak left ventricle to the aorta. The LVAD is controlled by the power supplied to the pump motor. An increase in the pump motor power increases the pump speed and the pump flow. The LVAD is typically controlled at a fixed setting of pump power. This basically means that the controller does not react to any change in the activity level of the patient. An important engineering challenge is to develop an LVAD feedback controller that can automatically adjusts its pump motor power so that the resulting pump flow matches the physiological demand of the patient. To this end, the development of a mathematical model that can be used to accurately simulate the interaction between the cardiovascular system of the patient and the LVAD is essential for the controller design. The use of such a dynamic model helps engineers and physicians in testing their theories, assessing the effectiveness of prescribed treatments, and understanding in depth the characteristics of this coupled bio-mechanical system.The first contribution of this dissertation is the development of a pump power-based model for the cardiovascular-LVAD system. Previously, the mathematical models in the literature assume availability of the pump speed as an independent control variable. In reality, however, the device is controlled by pump motor power which, in turn, produces the rotational pump speed. The nonlinear relationship between the supplied power and the speed is derived, and interesting observations about the pump speed signal are documented.The second contribution is the development of a feedback controller for patients using an LVAD as either a destination therapy or a bridge to transplant device. The main objective of designing this controller is to provide a physiological demand of the patient equivalent of that of a healthy individual. Since the device is implanted for a long period of time, this objective is chosen to allow the patient to live a life as close to normal as possible.The third contribution is an analysis of the aortic valve dynamics under the support of an LVAD. The aortic valve may experiences a permanent closure when the LVAD pump power is increased too much. The permanent closure of the aortic valve can be very harmful to the patients using the device as a bridge to recovery treatments. The analysis illustrates the various changes in the hemodynamic variables of the patient as a result of aortic valve closing. The results establish the relationship between the activity level and the heart failure severity with respect to the duration of the aortic valve opening.
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Date Issued: 2014
Identifier: CFE0005491, ucf:50354
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005491

Title: Nonlinear dispersive partial differential equations of physical relevance with applications to vortex dynamics.
Creator: VanGorder, Robert, Kaup, David, Vajravelu, Kuppalapalle, Nevai, Andrew, Mohapatra, Ram, Kassab, Alain, University of Central Florida
Abstract / Description: Nonlinear dispersive partial differential equations occur in a variety of areas within mathematical physics and engineering. We study several classes of such equations, including scalar complex partial differential equations, vector partial differential equations, and finally non-local integro-differential equations. For physically interesting families of these equations, we demonstrate the existence (and, when possible, stability) of specific solutions which are relevant for applications....
Show moreNonlinear dispersive partial differential equations occur in a variety of areas within mathematical physics and engineering. We study several classes of such equations, including scalar complex partial differential equations, vector partial differential equations, and finally non-local integro-differential equations. For physically interesting families of these equations, we demonstrate the existence (and, when possible, stability) of specific solutions which are relevant for applications. While multiple application areas are considered, the primary application that runs through the work would be the nonlinear dynamics of vortex filaments under a variety of physical models. For instance, we are able to determine the structure and time evolution of several physical solutions, including the planar, helical, self-similar and soliton vortex filament solutions in a quantum fluid. Properties of such solutions are determined analytically and numerically through a variety of approaches. Starting with complex scalar equations (often useful for studying two-dimensional motion), we progress through more complicated models involving vector partial differential equations and non-local equations (which permit motion in three dimensions). In many of the examples considered, the qualitative analytical results are used to verify behaviors previously observed only numerically or experimentally.
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Date Issued: 2014
Identifier: CFE0005272, ucf:50545
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005272

Title: A COUPLED CFD-LUMPED PARAMETER MODEL OF THE HUMAN CIRCULATION: ELUCIDATING THE HEMODYNAMICS OF THE HYBRID NORWOOD PALLIATIVE TREATMENT AND EFFECTS OF THE REVERSE BLALOCK-TAUSSIG SHUNT PLACEMENT AND DIAMETER.
Creator: Ceballos, Andres, Kassab, Alain, Bai, Yuanli, Deng, Weiwei, DeCampli, William, Divo, Eduardo, University of Central Florida
Abstract / Description: The Hybrid Norwood (HN) is a relatively new first stage procedure for neonates with Hypoplastic Left Heart Syndrome (HLHS), in which a sustainable univentricular circulation is established in a less invasive manner than with the standard procedure. A computational multiscale model of such HLHS circulation following the HN procedure was used to obtain detailed hemodynamics. Implementation of a reverse-BT shunt (RBTS), a synthetic bypass from the main pulmonary to the innominate artery placed...
Show moreThe Hybrid Norwood (HN) is a relatively new first stage procedure for neonates with Hypoplastic Left Heart Syndrome (HLHS), in which a sustainable univentricular circulation is established in a less invasive manner than with the standard procedure. A computational multiscale model of such HLHS circulation following the HN procedure was used to obtain detailed hemodynamics. Implementation of a reverse-BT shunt (RBTS), a synthetic bypass from the main pulmonary to the innominate artery placed to counteract aortic arch stenosis, and its effects on local and global hemodynamics were studied.A synthetic and a 3D reconstructed, patient derived anatomy after the HN procedure were utilized, with varying degrees of distal arch obstruction, or stenosis, (nominal and 90% reduction in lumen) and varying RBTS diameters (3.0, 3.5, 4.0 mm). A closed lumped parameter model (LPM) for the peripheral or distal circulation coupled to a 3D Computational Fluid Dynamics (CFD) model that allows detailed description of the local hemodynamics was created for each anatomy. The implementation of the RBTS in any of the chosen diameters under severe stenosis resulted in a restoration of arterial perfusion to near-nominal levels. Shunt flow velocity, vorticity, and overall wall shear stress levels are inverse functions of shunt diameter, while shunt perfusion and systemic oxygen delivery correlates positively with diameter. No correlation of shunt diameter with helicity was recorded.In the setting of the hybrid Norwood circulation, our results suggest: (1) the 4.0mm RBTS may be more thrombogenic when implemented in the absence of severe arch stenosis and (2) the 3.0mm and 3.5mm RBTS may be a more suitable alternative, with preference to the latter since it provides similar hemodynamics at lower levels of wall shear stress.
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Date Issued: 2015
Identifier: CFE0005772, ucf:50068
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005772

Title: Modeling and Spray Pyrolysis Processing of Mixed Metal Oxide Nano-Composite Gas Sensor Films.
Creator: Khatami, Seyed Mohammad Navid, Ilegbusi, Olusegun, Deng, Weiwei, Kassab, Alain, Coffey, Kevin, Divo, Eduardo, University of Central Florida
Abstract / Description: The role of sensor technology is obvious in improvement and optimization of many industrial processes. The sensor films, which are considered the core of chemical sensors, have the capability to detect the presence and concentration of a specific chemical substance. Such sensor films achieve selectivity by detecting the interaction of the specific chemical substance with the sensor material through selective binding, adsorption and permeation of analyte. This research focuses on development...
Show moreThe role of sensor technology is obvious in improvement and optimization of many industrial processes. The sensor films, which are considered the core of chemical sensors, have the capability to detect the presence and concentration of a specific chemical substance. Such sensor films achieve selectivity by detecting the interaction of the specific chemical substance with the sensor material through selective binding, adsorption and permeation of analyte. This research focuses on development and verification of a comprehensive mathematical model of mixed metal oxide thin film growth using spray pyrolysis technique (SPT). An experimental setup is used to synthesize mixed metal oxide films on a heated substrate. The films are analyzed using a variety of characterization tools. The results are used to validate the mathematical model. There are three main stages to achieve this goal: 1) A Lagrangian-Eulerian method is applied to develop a CFD model of atomizing multi-component solution. The model predicts droplet characteristics in flight, such as spatial distribution of droplet size and concentration. 2) Upon reaching the droplets on the substrate, a mathematical model of multi-phase transport and chemical reaction phenomena in a single droplet is developed and used to predict the deposition of thin film. The various stages of droplet morphology associated with surface energy and evaporation are predicted. 3) The processed films are characterized for morphology and chemical composition (SEM, XPS) and the data are used to validate the models as well as investigate the influence of process parameters on the structural characteristics of mixed metal oxide films. The structural characteristics are investigated of nano structured thin films comprising of ZnO, SnO2, ZnO+In2O3 and SnO2+In2O3 composites. The model adequately predicts the size distribution and film thickness when the nanocrystals are well-structured at the controlled temperature and concentration.
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Date Issued: 2014
Identifier: CFE0005817, ucf:50048
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005817

Title: Suction Detection and Feedback Control for the Rotary Left Ventricular Assist Device.
Creator: Wang, Yu, Simaan, Marwan, Qu, Zhihua, Haralambous, Michael, Kassab, Alain, Divo, Eduardo, University of Central Florida
Abstract / Description: The Left Ventricular Assist Device (LVAD) is a rotary mechanical pump that is implanted in patients with congestive heart failure to help the left ventricle in pumping blood in the circulatory system. The rotary type pumps are controlled by varying the pump motor current to adjust the amount of blood flowing through the LVAD. One important challenge in using such a device is the desire to provide the patient with as close to a normal lifestyle as possible until a donor heart becomes available...
Show moreThe Left Ventricular Assist Device (LVAD) is a rotary mechanical pump that is implanted in patients with congestive heart failure to help the left ventricle in pumping blood in the circulatory system. The rotary type pumps are controlled by varying the pump motor current to adjust the amount of blood flowing through the LVAD. One important challenge in using such a device is the desire to provide the patient with as close to a normal lifestyle as possible until a donor heart becomes available. The development of an appropriate feedback controller that is capable of automatically adjusting the pump current is therefore a crucial step in meeting this challenge. In addition to being able to adapt to changes in the patient's daily activities, the controller must be able to prevent the occurrence of excessive pumping of blood from the left ventricle (a phenomenon known as ventricular suction) that may cause collapse of the left ventricle and damage to the heart muscle and tissues.In this dissertation, we present a new suction detection system that can precisely classify pump flow patterns, based on a Lagrangian Support Vector Machine (LSVM) model that combines six suction indices extracted from the pump flow signal to make a decision about whether the pump is not in suction, approaching suction, or in suction. The proposed method has been tested using in vivo experimental data based on two different LVAD pumps. The results show that the system can produce superior performance in terms of classification accuracy, stability, learning speed, and good robustness compared to three other existing suction detection methods and the original SVM-based algorithm. The ability of the proposed algorithm to detect suction provides a reliable platform for the development of a feedback control system to control the current of the pump (input variable) while at the same time ensuring that suction is avoided.Based on the proposed suction detector, a new control system for the rotary LVAD was developed to automatically regulate the pump current of the device to avoid ventricular suction. The control system consists of an LSVM suction detector and a feedback controller. The LSVM suction detector is activated first so as to correctly classify the pump status as No Suction (NS) or Suction (S). When the detection is (")No Suction("), the feedback controller is activated so as to automatically adjust the pump current in order that the blood flow requirements of the patient's body at different physiological states are met according to the patient's activity level. When the detection is (")Suction("), the pump current is immediately decreased in order to drive the pump back to a normal No Suction operating condition. The performance of the control system was tested in simulations over a wide range of physiological conditions.
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Date Issued: 2013
Identifier: CFE0005070, ucf:49956
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005070

Title: Decentralized Power Management and Transient Control in Hybrid Fuel Cell Ultra-Capacitor System.
Creator: Madani, Seyed Omid, Das, Tuhin, Kassab, Alain, Lin, Kuo-Chi, Simaan, Marwan, University of Central Florida
Abstract / Description: Solid Oxide Fuel Cells (SOFCs) are considered suitable for alternative energy solutions due to advantages such as high efficiency, fuel flexibility, tolerance to impurities, and potential for combined cycle operations. One of the main operating constraints of SOFCs is fuel starvation, which can occur under fluctuating power demands. It leads to voltage loss and detrimental effects on cell integrity and longevity. In addition, reformer based SOFCs require sufficient steam for fuel reforming to...
Show moreSolid Oxide Fuel Cells (SOFCs) are considered suitable for alternative energy solutions due to advantages such as high efficiency, fuel flexibility, tolerance to impurities, and potential for combined cycle operations. One of the main operating constraints of SOFCs is fuel starvation, which can occur under fluctuating power demands. It leads to voltage loss and detrimental effects on cell integrity and longevity. In addition, reformer based SOFCs require sufficient steam for fuel reforming to avoid carbon deposition and catalyst degradation. Steam to carbon ratio (STCR) is an index indicating availability of the steam in the reformer. This work takes a holistic approach to address the aforementioned concerns in SOFCs, in an attempt to enhance applicability and adaptability of such systems. To this end, we revisit prior investigation on the invariant properties of SOFC systems, that led to prediction of fuel utilization U and STCR in the absence of intrusive and expensive sensing. This work provides further insight into the reasons behind certain SOFC variables being invariant with respect to operating conditions. The work extends the idea of invariant properties to different fuel and reformer types.In SOFCs, transient control is essential for U, especially if the fuel cell is to be operated in a dynamic load-following mode at high fuel utilization. In this research, we formulate a generalized abstraction of this transient control problem. We show that a multi-variable systems approach can be adopted to address this issue in both time and frequency domains, which leads to input shaping. Simulations show the effectiveness of the approach through good disturbance rejection. The work further integrates the aforementioned transient control research with system level control design for SOFC systems hybridized with storage elements. As opposed to earlier works where centralized robust controllers were of interest, here, separate controllers for the fuel cell and storage have been the primary emphasis. Thus, the proposed approach acts as a bridge between existing centralized controls for single fuel cells to decentralized control for power networks consisting of multiple elements. As a first attempt, decentralized control is demonstrated in a SOFC ultra-capacitor hybrid system. The challenge of this approach lies in the absence of direct and explicit communication between individual controllers. The controllers are designed based on a simple, yet effective principle of conservation of energy. Simulations as well as experimental results are presented to demonstrate the validity of these designs.
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Date Issued: 2014
Identifier: CFE0005524, ucf:50305
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005524

Title: DESIGN AND DEVELOPMENT OF HETEROGENOUS COMBUSTION SYSTEMS FOR LEAN BURN APPLICATIONS.
Creator: Terracciano, Anthony, Orlovskaya, Nina, Vasu Sumathi, Subith, Chow, Louis, Kassab, Alain, University of Central Florida
Abstract / Description: Combustion with a high surface area continuous solid immersed within the flame, referred to as combustion in porous media, is an innovative approach to combustion as the solid within the flame acts as an internal regenerator distributing heat from the combustion byproducts to the upstream reactants. By including the solid structure, radiative energy extraction becomes viable, while the solid enables a vast extension of flammability limits compared to conventional flames, while offering...
Show moreCombustion with a high surface area continuous solid immersed within the flame, referred to as combustion in porous media, is an innovative approach to combustion as the solid within the flame acts as an internal regenerator distributing heat from the combustion byproducts to the upstream reactants. By including the solid structure, radiative energy extraction becomes viable, while the solid enables a vast extension of flammability limits compared to conventional flames, while offering dramatically reduced emissions of NOx and CO, and dramatically increased burning velocities. Efforts documented within are used for the development of a streamlined set of design principles, and characterization of the flame's behavior when operating under such conditions, to aid in the development of future combustors for lean burn applications in open flow systems. Principles described herein were developed from a combination of experimental work and reactor network modeling using CHEMKIN-PRO. Experimental work consisted of a parametric analysis of operating conditions pertaining to reactant flow, combustion chamber geometric considerations and the viability of liquid fuel applications. Experimental behavior observed, when utilizing gaseous fuels, was then used to validate model outputs through comparing thermal outputs of both systems. Specific details pertaining to a streamlined chemical mechanism to be used in simulations, included within the appendix, and characterization of surface area of the porous solid are also discussed. Beyond modeling the experimental system, considerations are also undertaken to examine the applicability of exhaust gas recirculation and staged combustion as a means of controlling the thermal and environmental output of porous combustion systems. This work was supported by ACS PRF #51768-ND10 and NSF IIP 1343454.
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Date Issued: 2014
Identifier: CFE0005269, ucf:50549
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005269

Title: Biomechanical Models of Human Upper and Tracheal Airway Functionality.
Creator: Kuruppumullage, Don Nadun, Ilegbusi, Olusegun, Kassab, Alain, Moslehy, Faissal, Santhanam, Anand, Mansy, Hansen, Hoffman Ruddy, Bari, University of Central Florida
Abstract / Description: The respiratory tract, in other words, the airway, is the primary airflow path for several physiological activities such as coughing, breathing, and sneezing. Diseases can impact airway functionality through various means including cancer of the head and neck, Neurological disorders such as Parkinson's disease, and sleep disorders and all of which are considered in this study. In this dissertation, numerical modeling techniques were used to simulate three distinct airway diseases: a weak...
Show moreThe respiratory tract, in other words, the airway, is the primary airflow path for several physiological activities such as coughing, breathing, and sneezing. Diseases can impact airway functionality through various means including cancer of the head and neck, Neurological disorders such as Parkinson's disease, and sleep disorders and all of which are considered in this study. In this dissertation, numerical modeling techniques were used to simulate three distinct airway diseases: a weak cough leading to aspiration, upper airway patency in obstructive sleep apnea, and tongue cancer in swallow disorders. The work described in this dissertation, therefore, divided into three biomechanical models, of which fluid and particulate dynamics model of cough is the first. Cough is an airway protective mechanism, which results from a coordinated series of respiratory, laryngeal, and pharyngeal muscle activity. Patients with diminished upper airway protection often exhibit cough impairment resulting in aspiration pneumonia. Computational Fluid Dynamics (CFD) technique was used to simulate airflow and penetrant behavior in the airway geometry reconstructed from Computed Tomography (CT) images acquired from participants. The second study describes Obstructive Sleep Apnea (OSA) and the effects of dilator muscular activation on the human retro-lingual airway in OSA. Computations were performed for the inspiration stage of the breathing cycle, utilizing a fluid-structure interaction (FSI) method to couple structural deformation with airflow dynamics. The spatiotemporal deformation of the structures surrounding the airway wall was predicted and found to be in general agreement with observed changes in luminal opening and the distribution of airflow from upright to supine posture. The third study describes the effects of cancer of the tongue base on tongue motion during swallow. A three-dimensional biomechanical model was developed and used to calculate the spatiotemporal deformation of the tongue under a sequence of movements which simulate the oral stage of swallow.
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Date Issued: 2018
Identifier: CFE0007034, ucf:51986
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007034

CFD (8)	+ -
Combustion (7)	+ -
combustion (5)	+ -
heat transfer (5)	+ -
Computational Fluid Dynamics (4)	+ -

LVAD (4)	+ -
computational fluid dynamics (4)	+ -
Finite Element Analysis (3)	+ -
Heat Transfer (3)	+ -
Left Ventricular Assist Device (3)	+ -
Pavlik Harness (3)	+ -
Acoustic (2)	+ -
Anisotropy (2)	+ -
Autorotation (2)	+ -
Developmental (2)	+ -
Developmental Dysplasia of the Hip (2)	+ -
Fluid Structure Interaction (2)	+ -
Fused Deposition Modeling (2)	+ -
Ignition Delay Time (2)	+ -
Inverse Problem (2)	+ -
LPM (2)	+ -
Lean (2)	+ -
Lumper Parameter Model (2)	+ -
Meshless Methods (2)	+ -
Methane (2)	+ -
Modeling (2)	+ -
Optimization (2)	+ -
Parameter Estimation (2)	+ -
Premixed Combustion (2)	+ -
Proper Orthogonal Decomposition (2)	+ -

ETD Collection (86)	+ -
Honors Collection (9)	+ -

Kassab, Alain (95)	+ -
University of Central Florida (95)	+ -
Divo, Eduardo (19)	+ -
Kapat, Jayanta (19)	+ -
Vasu Sumathi, Subith (18)	+ -

Mansy, Hansen (14)	+ -
Bai, Yuanli (8)	+ -
Das, Tuhin (8)	+ -
Chow, Louis (6)	+ -
DeCampli, William (6)	+ -
Moslehy, Faissal (6)	+ -
Ahmed, Kareem (5)	+ -
Gordon, Ali (4)	+ -
Ilegbusi, Olusegun (4)	+ -
Ilie, Marcel (4)	+ -
Simaan, Marwan (4)	+ -
Chopra, Manoj (3)	+ -
Deng, Weiwei (3)	+ -
Gou, Jihua (3)	+ -
Kumar, Ranganathan (3)	+ -
Lin, Kuo-Chi (3)	+ -
Orlovskaya, Nina (3)	+ -
Peles, Yoav (3)	+ -
Qu, Zhihua (3)	+ -
Steward, Robert (3)	+ -
Beggs, Kyle (2)	+ -
Bhattacharya, Samik (2)	+ -
Ceballos, Andres (2)	+ -
Gerace, Salvadore (2)	+ -
Guimond, Stephen (2)	+ -

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