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Title: A MACHINE LEARNING APPROACH TO ASSESS THE SEPARATION OF SEISMOCARDIOGRAPHIC SIGNALS BY RESPIRATION.
Creator: Solar, Brian, Mansy, Hansen, University of Central Florida
Abstract / Description: The clinical usage of Seismocardiography (SCG) is increasing as it is being shown to be an effective non-invasive measurement for heart monitoring. SCG measures the vibrational activity at the chest surface and applications include non-invasive assessment of myocardial contractility and systolic time intervals. Respiratory activity can also affect the SCG signal by changing the hemodynamic characteristics of cardiac activity and displacing the position of the heart. Other clinically...
Show moreThe clinical usage of Seismocardiography (SCG) is increasing as it is being shown to be an effective non-invasive measurement for heart monitoring. SCG measures the vibrational activity at the chest surface and applications include non-invasive assessment of myocardial contractility and systolic time intervals. Respiratory activity can also affect the SCG signal by changing the hemodynamic characteristics of cardiac activity and displacing the position of the heart. Other clinically significant information, such as systolic time intervals, can thus manifest themselves differently in an SCG signal during inspiration and expiration. Grouping SCG signals into their respective respiratory cycle can mitigate this issue. Prior research has focused on developing machine learning classification methods to classify SCG events as according to their respiration cycle. However, recent research at the Biomedical Acoustics Research Laboratory (BARL) at UCF suggests grouping SCG signals into high and low lung volume may be more effective. This research aimed at com- paring the efficiency of grouping SCG signals according to their respiration and lung volume phase and also developing a method to automatically identify the respiration and lung volume phase of SCG events.
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Date Issued: 2018
Identifier: CFH2000310, ucf:45877
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000310

Title: Experimental and numerical investigation of a novel adsorption bed design for cooling applications.
Creator: Abdelhady, Ramy, Chow, Louis, Mansy, Hansen, Das, Tuhin, Duranceau, Steven, University of Central Florida
Abstract / Description: A global challenge is to develop environmentally friendly, affordable, compact and sustainable technologies to provide heating and cooling power. Adsorption cooling (AC) technology is one of the most promising ways to solve the environmental issues and cut down the energy consumption related to the traditional air conditioning and refrigeration systems. However, AC systems still suffer from poor heat and mass transfer inside the adsorption bed, which is the main obstacle to commercialization...
Show moreA global challenge is to develop environmentally friendly, affordable, compact and sustainable technologies to provide heating and cooling power. Adsorption cooling (AC) technology is one of the most promising ways to solve the environmental issues and cut down the energy consumption related to the traditional air conditioning and refrigeration systems. However, AC systems still suffer from poor heat and mass transfer inside the adsorption bed, which is the main obstacle to commercialization of adsorption cooling units. The main goal of this study is designing an efficient adsorption cooling cycle. In this research work, an in-depth scaling analysis of heat and mass transfer in an adsorption packed bed has been performed to identify and quantify how the effective thermal diffusivity of an adsorption bed and the surface diffusion rate of an adsorbate in a nanoporous adsorbent affect the specific cooling power of an adsorption cooling system. The main goal of this study is to derive new scaling parameters that can be used to specify the optimal bed dimensions and select the appropriate adsorbate/adsorbent pair to achieve the maximum cooling power. As the choice of a suitable working pair is critical for an adsorption cooling cycle, an experimental setup is designed and built to measure the adsorption kinetics and isotherms of any working pair accurately. This setup is also able to measure the dynamic performance of an adsorption bed. The equilibrium uptakes of Fuji silica-gels Type-RD and RD-2060 (manufactured by Fuji Silysia, Japan), which are commonly used in adsorption cooling systems, are measured experimentally. Based on the adsorption rate and the adsorbent temperature measured simultaneously, a new approach is proposed to measure the surface diffusivity in the temperature and pressure ranges typical of those during the operating conditions of adsorption cooling systems. In addition, the experimental measurements from the lab-scale adsorption bed are used to validate the numerical models that are commonly used for estimating the SCP of AC cycle. By using the scaling parameters driven from the scaling analysis, a newly designed packed bed for use in AC systems is proposed and evaluated in this research. The proposed design consists of repeated packed bed cells (modules). Each module is an open-cell aluminum foam packed with silica gel to enhance the overall thermal conductivity of the bed from 0.198 to 5.8 W/m.K. the experimental test rig is used to evaluate the performance on the new adsorption bed. The effect of pores per inch (PPI) of the foam, silica-gel particle size, bed height and adsorption isotherm of different types of silica gel on the bed performance are investigated.
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Date Issued: 2019
Identifier: CFE0007422, ucf:52702
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007422

Title: Dynamic Behavior and Performance of Different Types of Multi-Effect Desalination Plants.
Creator: Abdelkareem, Mohamed, Chow, Louis, Mansy, Hansen, Das, Tuhin, Duranceau, Steven, University of Central Florida
Abstract / Description: Water and energy are two of the most vital resources for the socio-economic development and sustenance of humanity on earth. Desalination of seawater has been practiced for some decades and is a well-established means of water supply. However, this process consumes large amounts of energy and the global energy supply is also faced with some challenges. In this research, multi-effect desalination (MED) has been selected due to lower cost, lower operating temperature and efficient in terms of...
Show moreWater and energy are two of the most vital resources for the socio-economic development and sustenance of humanity on earth. Desalination of seawater has been practiced for some decades and is a well-established means of water supply. However, this process consumes large amounts of energy and the global energy supply is also faced with some challenges. In this research, multi-effect desalination (MED) has been selected due to lower cost, lower operating temperature and efficient in terms of primary energy and electricity consumption compared to other thermal desalination systems. The motivation for this research is to address thermo-economics and dynamic behavior of different MED feed configurations with/without vapor compression (VC). A new formulation for the steady-state models was developed to simulate different MED systems. Adding a thermal vapor compressor (TVC) or mechanical vapor compression (MVC) unit to the MED system is also studied to show the advantage of this type of integration. For MED-TVC systems, results indicate that the parallel cross feed (PCF) configuration has better performance characteristics than other configurations. A similar study of MED-MVC systems indicates that the PCF and forward feed (FF) configurations require less work to achieve equal distillate production. Reducing the steam temperature supplied by the MVC unit leads to an increase in second law efficiency and a decrease in specific power consumption (SPC) and total water price. Following the fact that the MED may be exposed to fluctuations (disturbances) in input parameters during operation. Therefore, there is a requirement to analyze their transient behavior. In the current study, the dynamic model is developed based on solving the basic conservation equations of mass, energy, and salt. In the case of heat source disturbance, MED plants operating in the backward feed (BF) may be exposed to shut down due to flooding in the first effect. For all applied disturbances, the change in the brine level is the slowest compared to the changes in vapor temperature, and brine and vapor flow rates. For MED-TVC, it is recommended to limit the seawater cooling flow rate reduction to under 12% of the steady-state value to avoid dryout in the evaporators. A reduction in the motive steam flow rate and cooling seawater temperature of more than 20% and 35% of steady-state values, respectively, may lead to flooding in evaporators and plant shutdown. Simultaneous combinations of two different disturbances with opposing effects have only a modest effect on plant operation and they can be used to control and mitigate the flooding/drying effects caused by the disturbances. For the MED-MVC, the compressor work reduction could lead to plant shutdown, while a reduction in the seawater temperature will lead to a reduction in plant production and an increase in SPC.
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Date Issued: 2019
Identifier: CFE0007423, ucf:52735
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007423

Title: Characterization, Classification, and Genesis of Seismocardiographic Signals.
Creator: Taebi, Amirtaha, Mansy, Hansen, Kassab, Alain, Huang, Helen, Vosoughi, Azadeh, University of Central Florida
Abstract / Description: Seismocardiographic (SCG) signals are the acoustic and vibration induced by cardiac activity measured non-invasively at the chest surface. These signals may offer a method for diagnosing and monitoring heart function. Successful classification of SCG signals in health and disease depends on accurate signal characterization and feature extraction.In this study, SCG signal features were extracted in the time, frequency, and time-frequency domains. Different methods for estimating time-frequency...
Show moreSeismocardiographic (SCG) signals are the acoustic and vibration induced by cardiac activity measured non-invasively at the chest surface. These signals may offer a method for diagnosing and monitoring heart function. Successful classification of SCG signals in health and disease depends on accurate signal characterization and feature extraction.In this study, SCG signal features were extracted in the time, frequency, and time-frequency domains. Different methods for estimating time-frequency features of SCG were investigated. Results suggested that the polynomial chirplet transform outperformed wavelet and short time Fourier transforms.Many factors may contribute to increasing intrasubject SCG variability including subject posture and respiratory phase. In this study, the effect of respiration on SCG signal variability was investigated. Results suggested that SCG waveforms can vary with lung volume, respiratory flow direction, or a combination of these criteria. SCG events were classified into groups belonging to these different respiration phases using classifiers, including artificial neural networks, support vector machines, and random forest. Categorizing SCG events into different groups containing similar events allows more accurate estimation of SCG features.SCG feature points were also identified from simultaneous measurements of SCG and other well-known physiologic signals including electrocardiography, phonocardiography, and echocardiography. Future work may use this information to get more insights into the genesis of SCG.
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Date Issued: 2018
Identifier: CFE0007106, ucf:51944
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007106

Title: Fluid Dynamics Modeling and Sound Analysis of a Bileaflet Mechanical Heart Valve.
Creator: Khalili, Fardin, Mansy, Hansen, Kassab, Alain, Steward, Robert, Zaurin, Ricardo, University of Central Florida
Abstract / Description: Cardiovascular disease (CVD) is one of the main causes of death in the world. Some CVD involve severe heart valve disease that require valve replacement. There are more than 300,000 heart valves implanted worldwide, and about 85,000 heart valve replacements in the US. Approximately half of these valves are mechanical. Artificial valves may dysfunction leading to adverse hemodynamic conditions. Understanding the normal and abnormal valve function is important as it help improve valve designs....
Show moreCardiovascular disease (CVD) is one of the main causes of death in the world. Some CVD involve severe heart valve disease that require valve replacement. There are more than 300,000 heart valves implanted worldwide, and about 85,000 heart valve replacements in the US. Approximately half of these valves are mechanical. Artificial valves may dysfunction leading to adverse hemodynamic conditions. Understanding the normal and abnormal valve function is important as it help improve valve designs. Modeling of heart valve hemodynamics using computational fluid dynamics (CFD) provides a comprehensive analysis of flow, which can potentially help explain clinical observations and support therapeutic decision-making. This detailed information might not be accessible with in-vivo measurements. On the other hand, finite element analysis (FEA), is an efficient way to analyze the interactions of blood flow with blood vessel and tissue layers. In this project both CFD and FEA simulations were performed to investigate the flow-induced sound generation and propagation of sound waves through a tissue-like material. This method is based on mapping the transient pressure (force) fluctuations on the vessel wall and solving for the structural vibrations in the frequency domain. These vibrations would then be detected as sound on the epidermal surface. Advantages of the methods used in the current study include: (a) capability of providing accurate solution with a faster solution time; (b) inclusion of the fluid(-)structure interaction between blood flow and the arterial wall; and (c) accurately capturing some of the spectral features of the velocity fluctuation measured over the epidermal surface.
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Date Issued: 2018
Identifier: CFE0007029, ucf:52038
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007029

Title: Probing the Influence of Cx43 and Glucose on Endothelial Biomechanics.
Creator: Islam, Md Mydul, Steward, Robert, Kassab, Alain, Mansy, Hansen, Willenberg, Bradley, University of Central Florida
Abstract / Description: Endothelial cells (ECs) form the innermost layer of all vasculature and constantly receive both biochemical and biomechanical signals, yielding a plethora of biomechanical responses. In response to various biochemical or biomechanical cues, ECs have been documented to generate biomechanical responses such as tractions and intercellular stresses between the cell and substrate and between adjacent cells in a confluent monolayer, respectively. Thus far, the ability of endothelial tight junctions...
Show moreEndothelial cells (ECs) form the innermost layer of all vasculature and constantly receive both biochemical and biomechanical signals, yielding a plethora of biomechanical responses. In response to various biochemical or biomechanical cues, ECs have been documented to generate biomechanical responses such as tractions and intercellular stresses between the cell and substrate and between adjacent cells in a confluent monolayer, respectively. Thus far, the ability of endothelial tight junctions and adherens junctions to transmit intercellular stresses has been actively investigated, but the role of gap junctions is currently unknown. In addition, there is no report of the independent influence of hyperglycemia on endothelial biomechanics present in the literature. To fill these gaps, we conducted a two-fold study where we investigated the influence of endothelial gap junction Cx43 and hyperglycemia in endothelial tractions and intercellular stress generation. In the first study, we selectively disrupted and enhanced EC gap junction Cx43 by using 2',5'-dihydroxychalcone and retinoic acid, respectively and in the second study, we cultured ECs in both normal glucose and hyperglycemic condition for 10 days. In both studies, tractions and intercellular stresses were calculated using traction force microscopy (TFM) and monolayer stress microscopy (MSM), respectively. Our results reveal that Cx43 downregulation increased as well as decreased endothelial avg. normal intercellular stresses in response to a low (0.83 (&)#181;M) and a high dose (8.3 (&)#181;M) chalcone treatment, respectively, while Cx43 upregulation decreases avg. normal intercellular stresses in both treatment conditions (2.5 (&)#181;M and 25 (&)#181;M) compared to control. In addition, we observed a decrease in intercellular stresses with hyperglycemic condition compared to control. The results we present here represent, for the first time, detailed and comprehensive biomechanical analysis of endothelial cells under the influence of glucose and the gap junction Cx43. We believe our results will provide valuable insights into endothelial permeability, barrier strength as well as leading to a greater understanding of overall endothelial mechanics.
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Date Issued: 2019
Identifier: CFE0007819, ucf:52805
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007819

Title: Hybrid Multi-Objective Optimization of Left Ventricular Assist Device Outflow Graft Anastomosis Orientation to Minimize Stroke Rate.
Creator: Lozinski, Blake, Kassab, Alain, Mansy, Hansen, DeCampli, William, University of Central Florida
Abstract / Description: A Left Ventricular Assist Device (LVAD) is a mechanical pump that is utilized as a bridge to transplantation for patients with a Heart Failure (HF) condition. More recently, LVADs have been also used as destination therapy and have provided an increase in the quality of life for patients with HF. However, despite improvements in VAD design and anticoagulation treatment, there remains a significant problem with VAD therapy, namely drive line infection and thromboembolic events leading to...
Show moreA Left Ventricular Assist Device (LVAD) is a mechanical pump that is utilized as a bridge to transplantation for patients with a Heart Failure (HF) condition. More recently, LVADs have been also used as destination therapy and have provided an increase in the quality of life for patients with HF. However, despite improvements in VAD design and anticoagulation treatment, there remains a significant problem with VAD therapy, namely drive line infection and thromboembolic events leading to stroke. This thesis focuses on a surgical maneuver to address the second of these issues, guided by previous steady flow hemodynamic studies that have shown the potential of tailoring the VAD outflow graft (VAD-OG) implantation in providing up to 50% reduction in embolization rates. In the current study, multi-scale pulsatile hemodynamics of the VAD bed is modeled and integrated in a fully automated multi-objective shape optimization scheme in which the VAD-OG anastomosis along the Ascending Aorta (AA) is optimized to minimize the objective function which include thromboembolic events to the cerebral vessels and wall shear stress (WSS). The model is driven by a time dependent pressure and flow boundary conditions located at the boundaries of the 3D domain through a 50 degree of freedom 0D lumped parameter model (LPM). The model includes a time dependent multi-scale Computational Fluid Dynamics (CFD) analysis of a patient specific geometry. Blood rheology is modeled as using the non-Newtonian Carreua-Yasuda model, while the hemodynamics are that of a laminar and constant density fluid. The pulsatile hemodynamics are resolved using the commercial CFD solver StarCCM+ while a Lagrangian particle tracking scheme is used to track constant density particles modeling thromobi released from the cannula to determine embolization rated of thrombi. The results show that cannula anastomosis orientation plays a large role when minimizing the objective function for patient derived aortic bed geometry used in this study. The scheme determined the optimal location of the cannula is located at 5.5 cm from the aortic root, cannula angle at 90 degrees and coronal angle at 8 degrees along the AA with a peak surface average WSS of 55.97 dy/cm2 and stroke percentile of 12.51%. A Pareto front was generated showing the range of 9.7% to 44.08% for stroke and WSS of 55.97 to 81.47 dy/cm2 ranged over 22 implantation configurations for the specific case studied. These results will further assist in the treatment planning for clinicians when implementing a LVAD.
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Date Issued: 2019
Identifier: CFE0007833, ucf:52827
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007833

Title: Detection of DDH in Infants and Children Using Audible Acoustics.
Creator: Hassan, Tanvir, Mansy, Hansen, Song, Sang-Eun, Kassab, Alain, University of Central Florida
Abstract / Description: Detection of developmental dysplasia of the hip (DDH) in infants and children is important as it leads to permanent hip instability. Current methods for detecting DDH, such as ultrasound and x-rays, are relatively expensive and need qualified medical personnel to administer the test. Furthermore, x-ray ionizing radiation can have potential harmful effects. In the current study, an acoustic non-invasive and simple approach was investigated for detection of DDH. Different benchtop simplified...
Show moreDetection of developmental dysplasia of the hip (DDH) in infants and children is important as it leads to permanent hip instability. Current methods for detecting DDH, such as ultrasound and x-rays, are relatively expensive and need qualified medical personnel to administer the test. Furthermore, x-ray ionizing radiation can have potential harmful effects. In the current study, an acoustic non-invasive and simple approach was investigated for detection of DDH. Different benchtop simplified models and pig models were constructed and tested. Models were stimulated with band-limited white acoustic noise (10-2500 Hz) and the response of the models was measured. The power spectrum density, transfer function, and coherence were determined for different hip dysplasia levels and for normal cases. Results showed that the power spectrum density, transfer function, and coherence were affected by dysplasia occurrence. Effects appear larger for more severe dysplastic hips. This suggests that the proposed approach may have potential for DDH detection.
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Date Issued: 2019
Identifier: CFE0007816, ucf:52350
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007816

Title: Electrospray and Superlens Effect of Microdroplets for Laser-Assisted Nanomanufacturing.
Creator: Castillo Orozco, Eduardo, Kumar, Ranganathan, Mansy, Hansen, Peles, Yoav, University of Central Florida
Abstract / Description: Nanoparticles of various materials are known to exhibit excellent mechanical, chemical, electrical, and optical properties. However, it is difficult to deposit and transform nanoparticles into large two-dimensional and three-dimensional structures, such as thin films and discrete arrays. Electrospray technology and laser heating enable the deposition of these nanoparticles through the dual role of microdroplets as nanoparticle carriers and superlenses. The main goals of this dissertation are...
Show moreNanoparticles of various materials are known to exhibit excellent mechanical, chemical, electrical, and optical properties. However, it is difficult to deposit and transform nanoparticles into large two-dimensional and three-dimensional structures, such as thin films and discrete arrays. Electrospray technology and laser heating enable the deposition of these nanoparticles through the dual role of microdroplets as nanoparticle carriers and superlenses. The main goals of this dissertation are to delineate the electrospray modes, to achieve subwavelength focusing, and to enable a process for the deposition of nanoparticles into microlayers and discrete nanodots (a nanodot is a cluster of nanoparticles) on rigid and flexible substrates. This additive manufacturing process is based on the electrospray generation of water microdroplets that carry nanoparticles onto a substrate and the laser sintering of these nanoparticles. The process involves injecting nanoparticles (contained inside electric field-driven water microdroplets) into a hollow laser beam. The laser beam heats the droplets, causing the water to evaporate and the nanoparticles to sinter and form deposit of material on the substrate.The electrohydrodynamic inkjet printing of nanoparticle suspensions has been accomplished by the operation of an electrospray in microdripping mode and it allows the deposition of monodisperse microdroplets containing nanoparticles into discrete nanodot arrays, narrow lines, and thin films. For flow rates with low Reynolds number, the mode changes from dripping to microdripping mode, and then to a planar oscillating microdripping mode as the electric capillary number, Cae increases. The microdripping mode which is important for depositing discrete array of nanodots is found to occur in a narrow range, 2 ? Cae ? 2.5. The effect of the physical properties on the droplet size and frequency of droplet formation is more precisely described by the relative influence of the electric, gravity, viscous, and capillary forces. A scaling analysis is derived from a fundamental force balance and has yielded a parameter based on the electric capillary number, capillary number, and Bond number. Results for different nanoparticle suspensions with a wide range of physical properties show that the normalized radius of droplet, can be correlated using this parameter in both dripping and microdripping modes. The same parameter also correlates the normalized frequency of droplet formation, Nd* as an increasing function in the microdripping mode. Viscosity affects the shape of the cone by resisting its deformation and thus promoting a stable microdripping mode. Reduction in surface tension decreases the droplet size in the electrospray modes. However, the capillary size and electrical conductivity have minimal effect on the size of the ejected droplets. Electrical conductivity affects the transition between microdripping and oscillating microdripping modes. Based on this analysis, it is possible to design the electrospray to produce uniform monodisperse droplets by manipulating the voltage at the electrode, for any desired nanoparticle concentration of a suspension to be sintered on a substrate. For the fabrication of nanodots, a laser beam of wavelength ? = 1064 nm was focused to a diameter smaller than its wavelength. When the microdroplets did not carry nanoparticles, the subwavelength focusing of the laser yielded nanoholes smaller than its wavelength. Results show that tiny features with high resolution can be created by loading microdroplets with nanoparticles and squeezing the laser beam to subwavelength regions. Nanodots of silicon and germanium with diameters between 100 - 500 nm have been deposited on a silicon substrate. This study demonstrates an interdisciplinary mechanism to achieve subwavelength focusing in a laser process. In this process, the microdroplets serve as both a nanoparticle carrier and a superlens that focuses a laser beam to subwavelength diameters up to ? /10, thus overcoming the diffraction limit. The microdroplets are generated from a suspension of nanoparticles using an electrospray technique and the superlens characteristic of these microdroplets is attributed to three optical phenomena such as Maxwell's fish eye lens or L(&)#252;neberg lens, evanescent waves by laser scattering, and evanescent waves by the total internal reflection principle. A microfluidic cooling effect can also contribute to creating subwavelength features. In summary, this work describes a new laser-assisted additive manufacturing process for the fabrication of nanodots and microlayers using nanoparticles of different materials. In this process, microdroplets from an electrospray are used as nanoparticle carriers and superlenses to focus the laser to a diameter smaller than its wavelength. While this process is demonstrated to produce subwavelength holes and nanodots, the process is scalable to produce narrow lines and thin films of semiconductor materials by an additive manufacturing technique. This process extends the application of infrared lasers to the production of nanostructures and nanofeatures, and, therefore, provides a novel technology for nanomanufacturing.
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Date Issued: 2018
Identifier: CFE0007563, ucf:52579
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007563

Title: VARIABLE FLUID FLOW REGIMES ALTER ENDOTHELIAL ADHERENS JUNCTIONS AND TIGHT JUNCTIONS.
Creator: Ranadewa, Dilshan, Steward, Robert, Gou, Jihua, Mansy, Hansen, University of Central Florida
Abstract / Description: Variable blood flow regimes influence a range of cellular properties ranging from cell orientation, shape, and permeability: all of which are dependent on endothelial cell-cell junctions. In fact, cell-cell junctions have shown to be an integral part of vascular homeostasis through the endothelium by allowing intercellular signaling and passage control through tight junctions (TJs), adherens junctions (AJs), and gap junctions (GJs). It was our objective to determine the structural response of...
Show moreVariable blood flow regimes influence a range of cellular properties ranging from cell orientation, shape, and permeability: all of which are dependent on endothelial cell-cell junctions. In fact, cell-cell junctions have shown to be an integral part of vascular homeostasis through the endothelium by allowing intercellular signaling and passage control through tight junctions (TJs), adherens junctions (AJs), and gap junctions (GJs). It was our objective to determine the structural response of both AJs and TJs under steady and oscillatory flow. Human brain microvascular endothelial cells (HBMECs) were cultured in a parallel plate flow chamber and exposed to separate trails of steady and oscillatory fluid shear stress for 24 hours. Steady flow regimes consisted of a low laminar flow (LLF) of 1 dyne/cm2, and a high laminar flow (HLF) of 10 dyne/cm2 and oscillatory flow regimes consisted of low oscillatory flow (LOF) +/- 1 dyne/cm2 and high oscillatory flow (HLF) of +/- 10 dyne/cm2. We then imaged the TJs ZO-1 Claudin-5 and AJs JAM-A VE-Cadherin and subsequently analyzed their structural response as a function of pixel intensity. Our findings revealed an increase in pixel intensity between LLF and LOF along the boundary of the cells in both TJs ZO1 Claudin 5. Therefore, our results demonstrate the variable response of different cell-cell junctions under fluid shear, and for the first time, observes the difference in cell-cell junctional structure amongst steady and oscillatory flow regimes
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Date Issued: 2019
Identifier: CFE0007518, ucf:52618
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007518

Title: Computational Fluid Dynamics Study of Thromboembolism as a Function of Shunt Size and Placement in the Hybrid Norwood Palliative Treatment of Hypoplastic Left Heart Syndrome.
Creator: Seligson, John, Kassab, Alain, DeCampli, William, Mansy, Hansen, University of Central Florida
Abstract / Description: The Hybrid Norwood procedure has emerged as a promising alternative palliative first stage treatment for infants with Hypoplastic Left Heart Syndrome (HLHS). The procedure is done to provide necessary blood flow to the pulmonary and systemic regions of the body. The procedure can affect hemodynamic conditions to be pro-thrombotic, and thrombus particles can form and release from the vessel walls and enter the flow. Assuming these particles are formed and released from the shunt surface, a...
Show moreThe Hybrid Norwood procedure has emerged as a promising alternative palliative first stage treatment for infants with Hypoplastic Left Heart Syndrome (HLHS). The procedure is done to provide necessary blood flow to the pulmonary and systemic regions of the body. The procedure can affect hemodynamic conditions to be pro-thrombotic, and thrombus particles can form and release from the vessel walls and enter the flow. Assuming these particles are formed and released from the shunt surface, a Computational Fluid Dynamics (CFD) model can be used to mimic the patient's vasculature geometry and predict the occurrence of embolization to the carotid or coronary arteries, as well as the other major arteries surrounding the heart. This study used a time dependent, multi-scale CFD analysis on patient-specific geometry to determine the statistical probability of thrombus particles exiting each major artery. The geometries explored were of a nominal and patient specific nature. Cases of 90% and 0% stenosis at the aortic arch were analyzed, including shunt diameters of 3mm, 3.5mm, and 4mm. Three different placements of the shunt were explored as well. The intent of this study was to suggest best methods of surgical planning in the Hybrid Norwood procedure by providing supporting data for optimal stroke and myocardial infarction prevention.
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Date Issued: 2017
Identifier: CFE0006655, ucf:51232
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006655

Title: Theoretical And Experimental Investigation Of The Cascading Nature Of Pressure-Swirl Atomization.
Creator: Choudhury, Pretam, Kumar, Ranganathan, Deng, Weiwei, Mansy, Hansen, University of Central Florida
Abstract / Description: Pressure swirl atomizers are commonly used in IC, aero-engines, and liquid propellant rocket combustion. Understanding the atomization process is important in order to enhance vaporization, mitigate soot formation, design of combustion chambers, and improve overall combustion efficiency. This work utilizes non-invasive techniques such as ultra -speed imaging, and Phase Doppler Particle Anemometry (PDPA) in order to investigate the cascade atomization process of pressure-swirl atomizers by...
Show morePressure swirl atomizers are commonly used in IC, aero-engines, and liquid propellant rocket combustion. Understanding the atomization process is important in order to enhance vaporization, mitigate soot formation, design of combustion chambers, and improve overall combustion efficiency. This work utilizes non-invasive techniques such as ultra -speed imaging, and Phase Doppler Particle Anemometry (PDPA) in order to investigate the cascade atomization process of pressure-swirl atomizers by examining swirling liquid film dynamics and the localized droplet characteristics of the resulting hollow cone spray. Specifically, experiments were conducted to examine these effects for three different nozzles with orifice diameters .3mm, .5mm, and .97mm. The ultra-speed imaging allowed for both visualization and interface tracking of the swirling conical film which emanated from each nozzle. Moreover, this allowed for the measurement of the radial fluctuations, film length, cone angle and maximum wavelength. Radial fluctuations are found to be maximum near the breakup or rupture of a swirling film. Film length decreases as Reynolds number increases. Cone angle increases until a critical Reynolds number is reached, beyond which it remains constant. A new approach to analyze the temporally unstable waves was developed and compared with the measured maximum wavelengths. The new approach incorporates the attenuation of a film thickness, as the radius of a conical film expands, with the classical dispersion relationship for an inviscid moving liquid film. This approach produces a new long wave solution which accurately matches the measured maximum wavelength swirling conical films generated from nozzles with the smallest orifice diameter. For the nozzle with the largest orifice diameter, the new long wave solution provides the upper bound limit, while the long wave solution for a constant film thickness provides the lower bound limit. These results indicate that temporal instability is the dominating mechanism which generates long Kelvin Helmholtz waves on the surface of a swirling liquid film. The PDPA was used to measure droplet size and velocity in both the near field and far field of the spray. For a constant Reynolds number, an increase in orifice diameter is shown to increase the overall diameter distribution of the spray. In addition, it was found that the probability of breakup, near the axis, decreases for the largest orifice diameter. This is in agreement with the cascading nature of atomization.
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Date Issued: 2015
Identifier: CFE0006030, ucf:51012
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006030

Title: Brain stethoscope: A non-invasive method for monitoring intracranial pressure.
Creator: Azad, Md Khurshidul, Mansy, Hansen, Kassab, Alain, Bhattacharya, Samik, University of Central Florida
Abstract / Description: Monitoring intracranial pressure (ICP) is important for patients with increased intracranial pressure. Invasive methods of ICP monitoring include lumbar puncture manometry, which requires high precision, is costly, and can lead to complications. Non-invasive monitoring of ICP using tympanic membrane pulse (TMp) measurement can provide an alternative monitoring method that avoids such complications. In the current study, a piezo based sensor was designed, constructed and used to acquire TMp...
Show moreMonitoring intracranial pressure (ICP) is important for patients with increased intracranial pressure. Invasive methods of ICP monitoring include lumbar puncture manometry, which requires high precision, is costly, and can lead to complications. Non-invasive monitoring of ICP using tympanic membrane pulse (TMp) measurement can provide an alternative monitoring method that avoids such complications. In the current study, a piezo based sensor was designed, constructed and used to acquire TMp signals. The results showed that tympanic membrane waveform changed in morphology and amplitude with increased ICP, which was induced by changing subject position using a tilt table. In addition, the results suggest that TMp are affected by breathing, which has small effects on ICP. The newly developed piezo based brain stethoscope may be a way to monitor patients with increased intracranial pressure thus avoiding invasive ICP monitoring and reducing associated risk and cost.
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Date Issued: 2018
Identifier: CFE0006972, ucf:51643
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006972

Title: Droplet impact on deep liquid pools: secondary droplets formation from Rayleigh jet break-up and crown splash.
Creator: Castillo Orozco, Eduardo, Kumar, Ranganathan, Mansy, Hansen, Peles, Yoav, University of Central Florida
Abstract / Description: This work aims to study the impact of a droplet on liquid pools of the same fluid to understand the formation of secondary drops from the central jet and crown splash that occur after the impact. The impact of droplets on a deep pool has applications in cleaning up oil spill, spray cooling, painting, inkjet printing and forensic analysis, relying on the changes in properties such as viscosity, interfacial tension and density. Despite the exhaustive research on different aspects of droplet...
Show moreThis work aims to study the impact of a droplet on liquid pools of the same fluid to understand the formation of secondary drops from the central jet and crown splash that occur after the impact. The impact of droplets on a deep pool has applications in cleaning up oil spill, spray cooling, painting, inkjet printing and forensic analysis, relying on the changes in properties such as viscosity, interfacial tension and density. Despite the exhaustive research on different aspects of droplet impact, it is not clear how liquid properties can affect the instabilities leading to the Rayleigh jet breakup and the number of secondary drops formed after it pinches off. In this work, through systematic experiments, the droplet impact phenomena is investigated by varying viscosity and surface tension of liquids as well as impact speeds. Further, using a Volume-of-Fluid (VOF) method, it is shown that Rayleigh-Plateau instability is influenced by these parameters, and capillary timescale is the appropriate scale to normalize the breakup time. Increase in impact velocity increases the height of the thin column of fluid that emerges from the liquid pool. Under certain fluid conditions, the dissipation of this extra kinetic energy along with the surface tension forces produces instabilities at the neck of the jet. This could result in jet breakup and formation of secondary drops. In other words, both the formation of the jet and its breakup require a balance between viscous, capillary and surface tension forces. Based on Ohnesorge number (Oh) and impact Weber number (We), a regime map for no breakup, Rayleigh jet breakup, and crown splash is suggested for 0.0033 ? Oh ? 0.136. For Weber numbers beyond the critical value and Oh ? 0.091 the jet breakup occurs (Rayleigh jet breakup regime). While for Oh (>) 0.091, the jet breakup is suppressed regardless of the Weber number. In addition, high impact velocity initiates the crown formation and if further intensified it can disintegrate it into numerous secondary drops (crown splash) and it is observed to occur at all Ohnesorge numbers and high enough Weber numbers, however, at high Oh, a large portion of kinetic energy is dissipated, thus Rayleigh jet breakup is suppressed regardless of the magnitude of the impact velocity. Moreover, a correlation is proposed for normalized time with respect to the normalized maximum height of jet.
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Date Issued: 2015
Identifier: CFE0006278, ucf:51593
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006278

Title: Modeling of flow generated sound in a constricted duct at low Mach number.
Creator: Thibbotuwawa Gamage, Peshala, Mansy, Hansen, Kassab, Alain, Bhattacharya, Samik, University of Central Florida
Abstract / Description: Modelling flow and acoustics in a constricted duct at low Mach numbers is important for investigating many physiological phenomena such as phonation, generation of arterial murmurs, and pulmonary conditions involving airway obstruction. The objective of this study is to validate computational fluid dynamics (CFD) and computational aero-acoustics (CAA) simulations in a constricted tube at low Mach numbers. Different turbulence models were employed to simulate the flow field. Models included...
Show moreModelling flow and acoustics in a constricted duct at low Mach numbers is important for investigating many physiological phenomena such as phonation, generation of arterial murmurs, and pulmonary conditions involving airway obstruction. The objective of this study is to validate computational fluid dynamics (CFD) and computational aero-acoustics (CAA) simulations in a constricted tube at low Mach numbers. Different turbulence models were employed to simulate the flow field. Models included Reynolds Average Navier-Stokes (RANS), Detached eddy simulation (DES) and Large eddy simulation (LES). The models were validated by comparing study results with laser doppler anemometry (LDA) velocity measurements. The comparison showed that experimental data agreed best with the LES model results. Although RANS Reynolds stress transport (RST) model showed good agreement with mean velocity measurements, it was unable to capture velocity fluctuations. RANS shear stress transport (SST) k-? model and DES models were unable to predict the location of high fluctuating flow region accurately.CAA simulation was performed in parallel with LES using Acoustic Perturbation Equation (APE) based hybrid CAA method. CAA simulation results agreed well with measured wall sound pressure spectra. The APE acoustic sources were found in jet core breakdown region downstream of the constriction, which was also characterized by high flow fluctuations. Proper Orthogonal Decomposition (POD) is used to study the coherent flow structures at the different frequencies corresponding to the peaks of the measured sound pressure spectra. The study results will help enhance our understanding of sound generation mechanisms in constricted tubes including biomedical applications.
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Date Issued: 2017
Identifier: CFE0006920, ucf:51696
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006920

Title: A Multi-Scale CFD Analysis of Patient-Specific Geometries to Tailor LVAD Cannula Implantation Under Pulsatile Flow Conditions: an investigation aimed at reducing stroke incidence in LVADs.
Creator: Prather, Ray, Kassab, Alain, Mansy, Hansen, Divo, Eduardo, University of Central Florida
Abstract / Description: A Left Ventricular Assist Device (LVAD) is a mechanical pump that provides temporary circulatory support when used as bridge-to-transplantation and relieves workload demand placed on a failing heart allowing for myocardia recovery when used as destination therapy. Stroke is the most devastating complication after ventricular assist device (VAD) implantation, with an incidence of 14-47% over 3-6 months. This complication due to thrombus formation and subsequent transport through the...
Show moreA Left Ventricular Assist Device (LVAD) is a mechanical pump that provides temporary circulatory support when used as bridge-to-transplantation and relieves workload demand placed on a failing heart allowing for myocardia recovery when used as destination therapy. Stroke is the most devastating complication after ventricular assist device (VAD) implantation, with an incidence of 14-47% over 3-6 months. This complication due to thrombus formation and subsequent transport through the vasculature to cerebral vessels continues to limit the widespread implementation of VAD therapy. Patient-specific computational fluid dynamics (CFD) analysis may elucidate ways to reduce this risk.We employed a multi-scale model of the aortic circulation in order to examine the effects on flow conditions resulting from varying the VAD cannula implantation location and angle of incidence of the anastomosis to the ascending aorta based on a patient-specific geometry obtained from CT scans. The multi-scale computation consists of a 0D lumped parameter model (LPM) of the circulation modeled via a 50 degree of freedom (DOF) electrical circuit analogy that includes an LVAD model coupled to a 3D computational fluid dynamics model of the circulation. An in-house adaptive Runge-Kutta method is utilized to solve the 50 DOF LPM, and the Starccm+ CFD code is utilized to solve the flowfield. This 0D-3D coupling for the flow is accomplished iteratively with the 0D LPM providing the pulsatile boundary conditions that drive the 3D CFD time-accurate computations of the flowfield. Investigated angle configurations include cannula implantations at 30(&)deg;, 60(&)deg; and 90(&)deg; to the right lateral wall of the ascending aorta. We also considered placements of the VAD cannula along the ascending aorta in which distances of the VAD anastomosis is varied relative to the take-off of the innominate artery. We implemented a mixed Eulerian-Lagrangian particle-tracking scheme to quantify the number of stroke-inducing particles reaching cerebral vessel outlets and included flow visualization through streamlines to identify regions of strong vorticity and flow stagnation, which can promote thrombus formation. Thrombi were modeled as spheres with perfectly elastic interactions numerically released randomly in time and space at cannula inlet plane. Based on clinical observation of the range of thrombus sizes encountered in such cases, particle diameters of 2.5mm and 3.5mm were investigated in our numerical computations. Pulsatile flow results for aforementioned angles suggest that a 90(&)deg; cannula implementation causes flow impingement on the left lateral aortic wall and appears to be highly thrombogenic due to large momentum losses and zones of large re-circulation and that shallow and intermediate cannula angles promote more regular flow carrying particles towards the lower body potentially reducing stroke risk. Indications from this pulsatile numerical study suggest that up to a 50% reduction in stroke rate can be achieve with tailoring of cannula implantation. Results are consistent with significant reduction in stroke incidence achieved by tailoring cannula implantation as reported in previous steady flow computations carried out by our group. As such, results of this study suggest that a simple surgical maneuver in the process of VAD implantation may significantly improve patient life.
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Date Issued: 2015
Identifier: CFE0005689, ucf:50129
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005689

Title: Multi-scale fluid-structure interaction model analysis of patient-specific geometry for optimization of lvad outflow graft implantation: an investigation aimed at reducing stroke risk.
Creator: Prather, Ray, Kassab, Alain, Mansy, Hansen, Bai, Yuanli, Divo, Eduardo, DeCampli, William, University of Central Florida
Abstract / Description: A Left Ventricular Assist Device (LVAD), is a mechanical pump capable of(&)nbsp;providing circulatory myocardium relief when used as bridge-to-transplantation by reducing the workload of a failing heart, with the additional bonus of allowing for cardiac recovery when used as destination therapy. The newer generations of continuous flow VADs are essentially axial or radial flow pumps, and while these devices are capable their efficiency depends upon fluid composition and flow field patterns....
Show moreA Left Ventricular Assist Device (LVAD), is a mechanical pump capable of(&)nbsp;providing circulatory myocardium relief when used as bridge-to-transplantation by reducing the workload of a failing heart, with the additional bonus of allowing for cardiac recovery when used as destination therapy. The newer generations of continuous flow VADs are essentially axial or radial flow pumps, and while these devices are capable their efficiency depends upon fluid composition and flow field patterns. The most devastating complication of VAD therapy is caused by embolization of thrombi formed within the LVAD or inside the heart into the brain leading to stroke. Anticoagulation management and improved LVADs design has reduced stroke incidence, however, investigators have recently reported the incidence of thromboembolic cerebral events is still significant and ranges from 14% to 47% over a period of 6-12 months. Blood clots may cause obstruction of critical vessels, such as cerebral arteries, reducing brain oxygenation and resulting in devastating consequences like major neurocognitive malfunction and complications which can be fatal.The hypothesis that incidence of stroke can be significantly reduced by adjusting the VAD outflow cannula implantation to direct dislodged thrombi away from the cerebral vessels has been recently supported by a series of steady flow computations assuming rigid vessel walls for the vasculature. Such studies have shown as much as a 50% reduction in embolization rates depending on outflow cannula implantation. In this study, a pulsatile fully compliant vessel wall model is developed to further establish this hypothesis. A time-dependent multi-scale Eulerian Computational Fluid Dynamics (CFD) analysis of patient-specific geometry models of the VAD-bed vasculature is coupled with a 3D Finite Element Analysis (FEA) of the mechanical response of the vascular walls to establish the VAD assisted hemodynamics. A Lagrangian particle tracking algorithm is used to determine the embolization rates of thrombi emanating from the cannula or other possible thrombogenic locations such as the aortic root. This multiscale Eulerian-Lagrangian pulsatile fluid-structure coupled paradigm allows for a fully realistic model of the hemodynamics of interest. The patient-specific geometries obtained from CT scan are implemented into the numerical domain in two modes. In the 3D CFD portion of the problem, the geometry accounts solely for the flow volume where the fluid is modelled as constant density and non-Newtonian under laminar pulsatile flow conditions. The blood-thrombus ensemble in treated as a two-phase flow, handled by an Eulerian-Lagrangian coupled scheme to solve the flow field and track particle transport. Thrombi are modelled as constant density spherical particles. Particle interactions are limited to particle-to-wall and particle-to-fluid, while particle-to-particle interaction are neglected for statistical purposes. On the other hand, with the help of Computer Aided Design (CAD) software a patient-specific aortic wall geometry with variable wall thickness is brought into the numerical domain. FEA is applied to determine the aortic wall cyclic displacement under hydrodynamic loads. To properly account for wall deformation, the arterial wall tissue incorporates a hyperelastic material model based on the anisotropic Holzapfel model for arteries. This paradigm is referred to as Fluid Structure Interaction (FSI) and allows structural analysis in conjunction with flow investigation to further monitor pathological flow patterns. The FSI model is driven by time dependent flow and pressure boundary conditions imposed at the boundaries of the 3D computational domain through a 50 degree of freedom 0D lumped parameter model (LPM) electric circuit analog of the peripheral VAD-assisted circulation.Results are presented for a simple vessel model of the ascending aorta to validate the anisotropic fiber orientation implementation. Arterial wall dilation is measured between 5-20% in the range reported in literature. Hemodynamics of the VAD assisted flow in a patient-derived geometry computed using rigid vessels walls are compared to those for a linearly elastic vessel wall model and a hyperelastic anisotropic vessel wall model. Moreover, the thromboembolization rates are presented and compared for pulsatile hemodynamics in rigid and compliant wall models. Pulsatile flow solutions for embolization probabilities corroborate the hypothesis that tailoring the LVAD cannula implantation configuration can significantly reduce thromboembolization rates, and this is consistent with indications from previous steady-flow calculations.
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Date Issued: 2018
Identifier: CFE0007077, ucf:52017
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007077

Title: Investigation of a Self-powered Fontan Concept Using a Multiscale Computational Fluid-Structure Interaction Model.
Creator: Beggs, Kyle, Kassab, Alain, Steward, Robert, Mansy, Hansen, DeCampli, William, University of Central Florida
Abstract / Description: Congenital Heart Disease (CHD) occurs in about 1\% (40,000) of newborn babies each year in the United States alone. About 10.9\% (960) of whom suffer from Hypoplastic Left Heart Syndrome (HLHS) - a subset of CHD where children are born with a single-ventricle (SV). A series of three surgeries are carried out to correct HLHS culminating in the Fontan procedure where venous flow returns passively to the lungs. The current configuration for the Fontan results in elevated Central Venous Pressure ...
Show moreCongenital Heart Disease (CHD) occurs in about 1\% (40,000) of newborn babies each year in the United States alone. About 10.9\% (960) of whom suffer from Hypoplastic Left Heart Syndrome (HLHS) - a subset of CHD where children are born with a single-ventricle (SV). A series of three surgeries are carried out to correct HLHS culminating in the Fontan procedure where venous flow returns passively to the lungs. The current configuration for the Fontan results in elevated Central Venous Pressure (CVP), inadequate ventricular preload, and elevated Pulmonary Vascular Resistance (PVR) leading to a barrage of disease. To alleviate these complications, a `self-powered' Fontan is suggested where an Injection Jet Shunt (IJS) emanating from the aorta is anastomosed to each pulmonary artery. The IJS attempts to reduce the central venous pressure, increase preload, and aid in pulmonary arterial growth by entraining the flow with a high energy source provided by the aorta. Previous computational studies on this concept with rigid vessel walls show mild success, but not enough to be clinically relevant. It is hypothesized that vessel wall deformation may play an important role in enhancing the jet effect to provide a larger exit area for the flow to diffuse while also being more physiologically accurate. A multiscale 0D-3D tightly coupled Computational Fluid Dynamics (CFD) with Fluid-Structure Interaction (FSI) model is developed to investigate the efficacy of the proposed `self-powered' Fontan modification. Several runs are made varying the PVR to investigate the sensitivity of IVC pressure on PVR. IVC pressure decreased by 2.41 mmHg while the rigid wall study decreased the IVC pressure by 2.88 mmHg. It is shown that IVC pressure is highly sensitive to changes in PVR and modifications to the Fontan procedure should target aiding pulmonary arterial growth as it is the main indicator of Fontan success.
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Date Issued: 2018
Identifier: CFE0007311, ucf:52107
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007311

Title: Computational Fluid Dynamics Investigation of A Novel Hybrid Comprehensive Stage II Operation For Single Ventricle Palliation.
Creator: Hameed, Marwan, Kassab, Alain, DeCampli, William, Chow, Louis, Mansy, Hansen, Divo, Eduardo, University of Central Florida
Abstract / Description: Single ventricle (SV) anomalies account for one(&)#226;€"fourth of all cases of congenital heart disease. The existingthree hybrid staged surgical approach serving as a palliative treatment for this anomaly entails multiple complicationsand achieves a survival rate of only 50%. To reduce trauma associated with the second stage of the hybrid procedure,the hybrid comprehensive stage 2 (HCS2) operation was introduced in 2014 at Arnold Palmer Hospital in Orlando as anovel palliation alternative...
Show moreSingle ventricle (SV) anomalies account for one(&)#226;€"fourth of all cases of congenital heart disease. The existingthree hybrid staged surgical approach serving as a palliative treatment for this anomaly entails multiple complicationsand achieves a survival rate of only 50%. To reduce trauma associated with the second stage of the hybrid procedure,the hybrid comprehensive stage 2 (HCS2) operation was introduced in 2014 at Arnold Palmer Hospital in Orlando as anovel palliation alternative for a select subset of SV patients with adequate antegrade aortic flow. It avoids dissection ofthe pulmonary arteries by introducing a stented intrapulmonary baffle and avoids reconstruction of the aortic arch bymaintaining patency of the ductus arteriosus. This dissertation aims to provide better insight on the post-operativehemodynamics of HCS2 patients. A multi-scale Computational Fluid Dynamics (CFD) analysis of a synthetic,patient-derived HCS2 geometry based on unsteady laminar flow conditions and a non(&)#226;€"Newtonian blood model isutilized to quantify the resultant hemodynamics. The 3D CFD model is coupled to a 0D lumped parameter modelof the peripheral circulation that supplies the boundary conditions necessary to run the CFD analyses of the HCS2. Based on clinical parameters suggesting the baffle related narrowing to be at minimum 10mm and the pressuregradient not surpassing 20mmHg, hemodynamic analysis reveals that for even a 7.23mm narrowing the averagepressure drop across the baffle is 0.53mmHg. A peak pressure drop of 2.96mmHg was computed over the investigatedrange of clearances over the pulmonary baffle. Vortex shedding presents no concerns as the distance between the baffleand the aortic arch is much smaller compared to the length required for full vortices to form. Uneven contour distributionof the wall shear stress was observed due to the bend presented by the baffle that strongly affects the velocity profile inthe lumen across the pulmonary trunk and into the ductus arteriosus. Moreover, an oxygen transport model was derived,and the results showed consistency with the published data of Glenn patients. Particle residence time was also reported toidentify any blood recirculation or flow stagnation that may lead to platelet activation leading to clot formation rate.The study provides a range of main pulmonary artery geometries that, following multi-scale CFD analysis, present noconcerns regarding excessive pressure gradients or vortex formation. Moreover, the model identifies locations ofpotentially problematic hemodynamics that could be mitigated by shape optimization of the reconstruction.
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Date Issued: 2019
Identifier: CFE0007813, ucf:52340
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007813

Title: Mechanism of Hip Dysplasia and Identification of the Least Energy Path for its Treatment by using the Principle of Stationary Potential Energy.
Creator: Zwawi, Mohammed abdulwahab m, Moslehy, Faissal, Kassab, Alain, Mansy, Hansen, Divo, Eduardo, University of Central Florida
Abstract / Description: Developmental dysplasia of the hip (DDH) is a common newborn condition where the femoral head is not located in its natural position in the acetabulum (hip socket). Several treatment methods are being implemented worldwide to treat this abnormal condition. One of the most effective methods of treatment is the use of Pavlik Harness, which directs the femoral head toward the natural position inside the acetabulum. This dissertation presents a developed method for identifying the least energy...
Show moreDevelopmental dysplasia of the hip (DDH) is a common newborn condition where the femoral head is not located in its natural position in the acetabulum (hip socket). Several treatment methods are being implemented worldwide to treat this abnormal condition. One of the most effective methods of treatment is the use of Pavlik Harness, which directs the femoral head toward the natural position inside the acetabulum. This dissertation presents a developed method for identifying the least energy path that the femoral head would follow during reduction. This is achieved by utilizing a validated computational biomechanical model that allows the determination of the potential energy, and then implementing the principle of stationary potential energy. The potential energy stems from strain energy stored in the muscles and gravitational potential energy of four rigid-body components of lower limb bones. Five muscles are identified and modeled because of their effect on DDH reduction. Clinical observations indicate that reduction with the Pavlik Harness occurs passively in deep sleep under the combined effects of gravity and the constraints of the Pavlik Harness.A non-linear constitutive equation, describing the passive muscle response, is used in the potential energy computation. Different DDH abnormalities with various flexion, abduction, and hip rotation angles are considered, and least energy paths are identified. Several constraints, such as geometry and harness configuration, are considered to closely simulate real cases of DDH. Results confirm the clinical observations of two different pathways for closed reduction. The path of least energy closely approximated the modified Hoffman-Daimler method. Release of the pectineus muscle favored a more direct pathway over the posterior rim of the acetabulum. The direct path over the posterior rim of the acetabulum requires more energy. This model supports the observation that Grade IV dislocations may require manual reduction by the direct path. However, the indirect path requires less energy and may be an alternative to direct manual reduction of Grade IV infantile hip dislocations. Of great importance, as a result of this work, identifying the minimum energy path that the femoral head would travel would provide a non-surgical tool that effectively aids the surgeon in treating DDH.?
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Date Issued: 2015
Identifier: CFE0006022, ucf:51000
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006022

CFD (4)	+ -
Computational Fluid Dynamics (2)	+ -
LVAD (2)	+ -
Left Ventricular Assist Device (2)	+ -
Lumper Parameter Model (2)	+ -

classification (2)	+ -
machine learning (2)	+ -
Acoustic (1)	+ -
Adsorption cooling cycle (1)	+ -
Aspiration (1)	+ -
Bileaflet mechanical heart valve (1)	+ -
Biofluids (1)	+ -
Biomechanical Model (1)	+ -
Biomechanical Modeling (1)	+ -
COMSOL (1)	+ -
Cannula (1)	+ -
Cell Mechanics (1)	+ -
Cell encapsulation (1)	+ -
Cell-Cell Junctions (1)	+ -
Computational Aero-acoustics simulation (1)	+ -
Conginital (1)	+ -
Cost flow diagram (1)	+ -
Cough Dynamical Model (1)	+ -
Developmental (1)	+ -
Developmental Dysplasia of the Hip (1)	+ -
Droplet impact (1)	+ -
Droplet manipulation (1)	+ -
Dynamic disturbance (1)	+ -
Embolism (1)	+ -
Endothelial Cell (1)	+ -

ETD Collection (21)	+ -
Honors Collection (1)	+ -

Mansy, Hansen (22)	+ -
University of Central Florida (22)	+ -
Kassab, Alain (14)	+ -
DeCampli, William (5)	+ -
Divo, Eduardo (4)	+ -

Kumar, Ranganathan (4)	+ -
Steward, Robert (4)	+ -
Chow, Louis (3)	+ -
Bhattacharya, Samik (2)	+ -
Castillo Orozco, Eduardo (2)	+ -
Das, Tuhin (2)	+ -
Deng, Weiwei (2)	+ -
Duranceau, Steven (2)	+ -
Moslehy, Faissal (2)	+ -
Peles, Yoav (2)	+ -
Prather, Ray (2)	+ -
Abdelhady, Ramy (1)	+ -
Abdelkareem, Mohamed (1)	+ -
Azad, Md Khurshidul (1)	+ -
Bai, Yuanli (1)	+ -
Beggs, Kyle (1)	+ -
Cho, Hyoung Jin (1)	+ -
Choudhury, Pretam (1)	+ -
Davanlou, Ashkan (1)	+ -
Gou, Jihua (1)	+ -
Hameed, Marwan (1)	+ -
Hassan, Tanvir (1)	+ -
Hoffman Ruddy, Bari (1)	+ -
Huang, Helen (1)	+ -
Ilegbusi, Olusegun (1)	+ -

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