Indiana University-Purdue University Indianapolis (IUPUI) / The thesis includes two application studies of computational fluid dynamics. The first is new and efficient drug delivery to the posterior part of the eye, a growing health necessity worldwide. Current treatment of eye diseases, such as age-related macular degeneration (AMD), relies on repeated intravitreal injections of drug-containing solutions. Such a drug delivery has significant cant drawbacks, including short drug life, vital medical service, and high medical costs. In this study, we explore a new approach of controlled drug delivery by introducing unique porous implants. Computational modeling contains physiological and anatomical traits. We simulate the IgG1 Fab drug delivery to the posterior eye to evaluate the effectiveness of the porous implants to control the drug delivery. The computational model was validated by established computation results from independent studies and experimental data. Overall, the results indicate that therapeutic drug levels in the posterior eye are sustained for eight weeks, similar to those performed with intravitreal injection of the same drug. We evaluate the effects of the porous implant on the time evaluation of the drug concentrations in the sclera, choroid, and retina layers of the eye. Subsequent simulations were carried out with varying porosity values of a porous episcleral implant. Our computational results reveal that the time evolution of drug concentration is distinctively correlated to drug source location and pore size. The response of this porous implant for controlled drug delivery applications was examined. A correlation between porosity and fluid properties for the porous implants was revealed in this study. The second application lays in the computational modeling of the oscillating

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No description available.

Non-pulsatile and pulsatile flow in bent pipes and radial turbine has been assessed with numerical simulations. The flow field in a single bent pipe has been computed with different turbulence modelling approaches. A comparison with measured data shows that Implicit Large Eddy Simulation (ILES) gives the best agreement in terms of mean flow quantities. All computations with the different turbulence models qualitatively capture the so called Dean vortices. The Dean vortices are a pair of counter-rotating vortices that are created in the bend, due to inertial effects in combination with a radial pressure gradient. The pulsatile flow in a double bent pipe has also been considered. In the first bend, the Dean vortices are formed and in the second bend a swirling motion is created, which will together with the Dean vortices create a complex flow field downstream of the second bend. The strength of these structures will vary with the amplitude of the axial flow. For pulsatile flow, a phase shift between the velocity and the pressure occurs and the phase shift is not constant during the pulse depending on the balance between the different terms in the Navier- Stokes equations. The performance of a radial turbocharger turbine working under both non-pulsatile and pulsatile flow conditions has also been investigated by using ILES. To assess the effect of pulsatile inflow conditions on the turbine performance, three different cases have been considered with different frequencies and amplitude of the mass flow pulse and different rotational speeds of the turbine wheel. The results show that the turbine cannot be treated as being quasi-stationary; for example, the shaft power varies with varying frequency of the pulses for the same amplitude of mass flow. The pulsatile flow also implies that the incidence angle of the flow into the turbine wheel varies during the pulse. For the worst case, the relative incidence angle varies from approximately −80° to +60°. A phase shift between the pressure and the mass flow at the inlet and the shaft torque also occurs. This phase shift increases with increasing frequency, which affects the accuracy of the results from 1-D models based on turbine maps measured under non-pulsatile conditions. For a turbocharger working under internal combustion engine conditions, the flow into the turbine is pulsatile and there are also unsteady secondary flow components, depending on the geometry of the exhaust manifold situated upstream of the turbine. Therefore, the effects of different perturbations at the inflow conditions on the turbine performance have been assessed. For the different cases both turbulent fluctuations and different secondary flow structures are added to the inlet velocity. The results show that a non-disturbed inlet flow gives the best performance, while an inflow condition with a certain large scale eddy in combination with turbulence has the largest negative effect on the shaft power output. / QC 20101111

Understanding the mechanisms of cardiovascular disease progression is essential in developing novel therapies to combat this disease that contributes to 1 in 3 deaths in the United States every year. Endothelial dysfunction and its effects on vessel growth and remodeling are key factors in the progression and localization of atherosclerosis. Much of our understanding in this area has come from in-vivo and in-vitro experiments however perfused organ culture systems provide an alternative approach. Organ culture systems can provide a more controlled mechanical and biochemical environment compared to in-vivo models. This study focused on furthering development of this organ culture model by introducing a novel device to produce flow waveforms at the high frequencies and low mean flows seen in the mouse model. The device is capable of monitoring pressure, flow, diameter, and nitric oxide release. Each individual mechanism in the system was integrated via a computer using a custom Labview interface. The performance of the device was characterized by developing physiologic, physiologic-oscillatory, low, low-oscillatory waveforms and sinusoidal waveforms at frequencies ranging from 1-10 Hz. Overall this system provides a robust model to test the effects of flow on various biological markers both in real-time and after culture.

This thesis is motivated by the necessity to understand the flow structure of turbulent flows in bends encountered in many technical applications such as heat exchangers, nuclear reactors and internal combustion engines. Flows in bends are characterised by strong secondary motions in terms of counter-rotating vortices (Dean cells) set up by a centrifugal instability. Specifically the thesis deals with turbulent flows in 90° curved pipes of circular cross-section with and without an additional motion, swirling or pulsatile, superposed on the primary flow.  The aim of the present thesis is to study these complex flows in detail by using time-resolved stereoscopic particle image velocimetry to obtain the three-dimensional velocity field, with complementary hot-wire anemometry and laser Doppler velocimetry measurements. In order to analyse the vortical flow field proper orthogonal decomposition (POD) is used. The so called ``swirl-switching'' is identified and it is shown that the vortices instantaneously, ``rock'' between three states, viz. a pair of symmetric vortices or a dominant clockwise or counter-clockwise Dean cell. The most energetic mode exhibits a single cell spanning the whole cross-section and ``rolling'' (counter-)clockwise in time. However, when a honeycomb is mounted at the inlet of the bend, the Dean vortices break down and there is strong indication that the ``swirl-switching'' is hindered. When a swirling motion is superimposed on the incoming flow, the Dean vortices show a tendency to merge into a single cell with increasing swirl intensity. POD analysis show vortices which closely resemble the Dean cells, indicating that these structures co-exist with the swirling motion. In highly pulsating turbulent flow at the exit of a curved pipe, the vortical pattern is diminished or even eliminated during the acceleration phase and then re-established during the deceleration. In order to investigate the effect of pulsations and curvature on the performance of a turbocharger turbine, highly pulsating turbulent flow through a sharp bend is fed into the turbine. Time-resolved pressure and mass-flow rate measurements show that the hysteresis loop in the pressure-ratio-mass-flow plane, may differ significantly between straight and curved inlets, however the mean operating point is only slightly affected. / <p>QC 20140523</p>

Diss. Linköping : University, 2004.

abstract: Aortic pathologies such as coarctation, dissection, and aneurysm represent a particularly emergent class of cardiovascular diseases and account for significant cardiovascular morbidity and mortality worldwide. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these pathologies and for planning their surgical repair. In vitro experiments are required to validate these simulations against real world data, and a pulsatile flow pump system can provide physiologic flow conditions characteristic of the aorta. This dissertation presents improved experimental techniques for in vitro aortic blood flow and the increasingly larger parts of the human cardiovascular system. Specifically, this work develops new flow management and measurement techniques for cardiovascular flow experiments with the aim to improve clinical evaluation and treatment planning of aortic diseases. The hypothesis of this research is that transient flow driven by a step change in volume flux in a piston-based pulsatile flow pump system behaves differently from transient flow driven by a step change in pressure gradient, the development time being substantially reduced in the former. Due to this difference in behavior, the response to a piston-driven pump can be predicted in order to establish inlet velocity and flow waveforms at a downstream phantom model. The main objectives of this dissertation were: 1) to design, construct, and validate a piston-based flow pump system for aortic flow experiments, 2) to characterize temporal and spatial development of start-up flows driven by a piston pump that produces a step change from zero flow to a constant volume flux in realistic (finite) tube geometries for physiologic Reynolds numbers, and 3) to develop a method to predict downstream velocity and flow waveforms at the inlet of an aortic phantom model and determine the input waveform needed to achieve the intended waveform at the test section. Application of these newly improved flow management tools and measurement techniques were then demonstrated through in vitro experiments in patient-specific coarctation of aorta flow phantom models manufactured in-house and compared to computational simulations to inform and execute future experiments and simulations. / Dissertation/Thesis / Doctoral Dissertation Bioengineering 2015

Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-26Bitstream added on 2014-06-13T19:14:28Z : No. of bitstreams: 1 cicigliano_ecs_me_ilha.pdf: 2408732 bytes, checksum: 0af63a8f55dcecc2b890effc02c98e0e (MD5) / O presente trabalho propõe-se a modelar, analisar, e comparar os efeitos do escoamento de um fluido dentro de um tubo elástico. Esses efeitos, por sua vez, serão ocasionados por uma variação de pressão nesse fluido. Para tanto, através das propriedades físicas e mecânicas do tubo e do fluido, foi calculado o deslocamento da parede do tubo, vazão e velocidade do fluido. Essa modelagem tem como intenção comparar numericamente um arranjo que visa simular uma pulsação com características próximas as do coração humano. Através da construção de duas geometrias cilíndricas que representam domínios distintos (estrutura e fluido) que foram acoplados em sua interface, foi possível fazer um estudo da interação fluido-estrutura (FSI) utilizando o software comercial ANSYS, obtendo assim um estudo tri-dimensional do problema. Os resultados mostraram que o deslocamento da interface fluido-estrutura ocorreu simultaneamente, confirmando, portanto, a correta aplicação do comando FSIN. O fluido é considerado incompressível e Newtoniano e é governado pelas equações de Navier-Stokes. As paredes da estrutura são modeladas a partir da Lei de Hooke. Por fim, uma solução numérica é desenvolvida utilizando o Método dos Elementos Finitos / This project proposes to model, analyze and compare the effects of fluid flow inside an elastic tube. These effects, in turn, will be caused by a variation of pressure in this fluid. Therefore, through the physical and mechanical properties of the tube and fluid was calculated the displacement of the tube wall, flow and velocity of the fluid. The Modeling intends to compare numerically an arrangement that aims to simulate a heartbeat with characteristics similar to the human heart. Through of building two cylindrical geometries representing different domains (structure and fluid) that were engaged in its interface, it was possible to study the fluid-structure interaction (FSI) using the commercial software ANSYS, thereby obtaining a three-dimensional study. The results showed that the displacement of the interface fluid-structure occurred simultaneously, thereby confirming the correct application of the command FSIN. The fluid is considered incompressible and Newtonian and is governed by the Navier-Stokes equations. The walls of the structure are modeled from the Hooke's Law. Finally, a numerical solution is developed using the Finite Element Method

Resumo: O presente trabalho propõe-se a modelar, analisar, e comparar os efeitos do escoamento de um fluido dentro de um tubo elástico. Esses efeitos, por sua vez, serão ocasionados por uma variação de pressão nesse fluido. Para tanto, através das propriedades físicas e mecânicas do tubo e do fluido, foi calculado o deslocamento da parede do tubo, vazão e velocidade do fluido. Essa modelagem tem como intenção comparar numericamente um arranjo que visa simular uma pulsação com características próximas as do coração humano. Através da construção de duas geometrias cilíndricas que representam domínios distintos (estrutura e fluido) que foram acoplados em sua interface, foi possível fazer um estudo da interação fluido-estrutura (FSI) utilizando o software comercial ANSYS, obtendo assim um estudo tri-dimensional do problema. Os resultados mostraram que o deslocamento da interface fluido-estrutura ocorreu simultaneamente, confirmando, portanto, a correta aplicação do comando FSIN. O fluido é considerado incompressível e Newtoniano e é governado pelas equações de Navier-Stokes. As paredes da estrutura são modeladas a partir da Lei de Hooke. Por fim, uma solução numérica é desenvolvida utilizando o Método dos Elementos Finitos / Abstract: This project proposes to model, analyze and compare the effects of fluid flow inside an elastic tube. These effects, in turn, will be caused by a variation of pressure in this fluid. Therefore, through the physical and mechanical properties of the tube and fluid was calculated the displacement of the tube wall, flow and velocity of the fluid. The Modeling intends to compare numerically an arrangement that aims to simulate a heartbeat with characteristics similar to the human heart. Through of building two cylindrical geometries representing different domains (structure and fluid) that were engaged in its interface, it was possible to study the fluid-structure interaction (FSI) using the commercial software ANSYS, thereby obtaining a three-dimensional study. The results showed that the displacement of the interface fluid-structure occurred simultaneously, thereby confirming the correct application of the command FSIN. The fluid is considered incompressible and Newtonian and is governed by the Navier-Stokes equations. The walls of the structure are modeled from the Hooke's Law. Finally, a numerical solution is developed using the Finite Element Method / Orientador: Gilberto Pechoto de Melo / Coorientador: Amarildo Tabone Paschoalini / Banca: Adyles Arato Junior / Banca: Marcio Higa / Mestre