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A study of blood flow in normal and dilated aortaDeep, Debanjan 12 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Atherosclerotic lesions of human beings are common diagnosed in regions of arte- rial branching and curvature. The prevalence of atherosclerosis is usually associated with hardening and ballooning of aortic wall surfaces because of narrowing of flow path by the deposition of fatty materials, platelets and influx of plasma through in- timal wall of Aorta. High Wall Shear Stress (WSS) is proved to be the main cause behind all these aortic diseases by physicians and researchers. Due to the fact that the atherosclerotic regions are associated with complex blood flow patterns, it has believed that hemodynamics and fluid-structure interaction play important roles in regulating atherogenesis. As one of the most complex flow situations found in cardio- vascular system due to the strong curvature effects, irregular geometry, tapering and branching, and twisting, theoretical prediction and in vivo quantitative experimental data regarding to the complex blood flow dynamics are substantial paucity. In recent years, computational fluid dynamics (CFD) has emerged as a popular research tool to study the characteristics of aortic flow and aim to enhance the understanding of the underlying physics behind arteriosclerosis. In this research, we study the hemo- dynamics and flow-vessel interaction in patient specific normal (healthy) and dilated (diseased) aortas using Ansys-Fluent and Ansys-Workbench. The computation con- sists of three parts: segmentation of arterial geometry for the CFD simulation from computed tomography (CT) scanning data using MIMICS; finite volume simulation of hemodynamics of steady and pulsatile flow using Ansys-Fluent; an attempt to perform the Fluid Structure Simulation of the normal aorta using Ansys-Workbench. Instead of neglecting the branching or smoothing out the wall for simplification as a
lot of similar computation in literature, we use the exact aortic geometry. Segmen- tation from real time CT images from two patients, one young and another old to represent healthy and diseased aorta respectively, is on MIMICS. The MIMICS seg- mentation operation includes: first cropping the required part of aorta from CT dicom data of the whole chest, masking of the aorta from coronal, axial and saggital views of the same to extract the exact 3D geometry of the aorta. Next step was to perform surface improvement using MIMICS 3-matic module to repair for holes, noise shells and overlapping triangles to create a good quality surface of the geometry. A hexahe- dral volume mesh was created in T-Grid. Since T-grid cannot recognize the geometry format created by MIMICS 3-matic; the required step geometry file was created in Pro-Engineer. After the meshing operation is performed, the mesh is exported to Ansys Fluent to perform the required fluid simulation imposing adequate boundary conditions accordingly. Two types of study are performed for hemodynamics. First is a steady flow driven by specified parabolic velocity at inlet. We captured the flow feature such as skewness of velocity around the aortic arch regions and vortices pairs, which are in good agreement with open data in literature. Second is a pulsatile flow. Two pulsatile velocity profiles are imposed at the inlet of healthy and diseased aorta respectively. The pulsatile analysis was accomplished for peak systolic, mid systolic and diastolic phase of the entire cardiac cycle. During peak systole and mid-systole, high WSS was found at the aortic branch roots and arch regions and diastole resulted in flow reversals and low WSS values due to small aortic inflow. In brief, areas of sudden geometry change, i.e. the branch roots and irregular surfaces of the geom- etry experience more WSS. Also it was found that dilated aorta has more sporadic nature of WSS in different regions than normal aorta which displays a more uniform WSS distribution all over the aorta surface. Fluid-Structure Interaction simulation is performed on Ansys-WorkBench through the coupling of fluid dynamics and solid mechanics. Focus is on the maximum displacement and equivalent stress to find out the future failure regions for the peak velocity of the cardiac cycle.
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The Effect of Flow on the Development and Retention of Iron Sulfide Corrosion ProductLayersAnyanwu, Ezechukwu John 04 June 2019 (has links)
No description available.
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Improvements in Engine Performance Simulations and Integrated Engine Thermal ModelingAishwarya Vinod Ponkshe (16648650) 26 July 2023 (has links)
<p>One of the major challenges in the field of internal combustion engines is keeping up with the advancements in electrification and hybridization. Automakers are striving to design environment – friendly and highly efficient engines to meet stringent emission standards worldwide. Improving engine efficiency and reducing heat losses are critical aspects of this development. Therefore, accurate heat transfer prediction capabilities play a vital role in engine design process. Current methods rely on computationally intensive 3D numerical analyses, there is a growing interest in reliable simplified models. </p>
<p>In this study, a 1D diesel engine model featuring predictive combustion was integrated with a detailed finite element thermal primitive based on the 3D meshing feature available in GT Suite. Coolant and oil hydraulic circuits were incorporated in the model. The model proves to be an effective means to assess the impact on heat rejection and engine heat distribution given by an engine calibration and operating conditions. </p>
<p>This work also contributes to the advancement of virtual IC engine development methods by focusing on the design and tuning of complex engine system models using GT Power for accurate prediction of engine performance. The current processes in engine simulations are assessed to identify sources of errors and opportunities for improvements. The methods discussed in this work include isolated sub system level calibration and model evolution specifically address the issue of identifying noise factors and issues in smaller parts. Additionally, the study aims on improving the model’s trustworthiness by computing 1st law sanity checks, replicating real-life compressor map calculations and refining GT’s existing global convergence criteria. </p>
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[en] CFD SIMULATION OF THE FLOW IN THE HYDRAULIC CIRCUITS OF AN ONLINE HEAT EXCHANGER CLEANING DEVICE / [pt] SIMULAÇÃO CFD DO ESCOAMENTO NOS CIRCUITOS HIDRÁULICOS DE UM DISPOSITIVO DE LIMPEZA ONLINE DE TROCADORES DE CALORSERGIO LUIS DE LA HOZ TRUYOLL 09 July 2024 (has links)
[pt] Trocadores de calor são equipamentos essenciais do sistema de resfriamento de
equipamentos de processo, visando assegurar a sua eficácia e eficiência
operacional. O objetivo do trabalho é a simulação computacional do escoamento
do fluido de transporte dos artefatos de limpeza de uma alternativa tecnológica de
trocadores de calor que dispensa a interrupção do processo industrial. A motivação
resultou do potencial da ferramenta computacional CFD em gerar resultados
numéricos de interesse, complementando a base de dados experimentais em locais
críticos do escoamento difíceis de serem instrumentados. A simulação foi realizada
pelo Fluent/Ansys 2023 R2, utilizando-se o modelo de turbulência κ-ômega SST
(Transporte da tensão de cisalhamento), baseado na abordagem média de Reynolds
(RANS - Reynolds-Averaged Navier-Stokes). Os resultados da simulação (campos
de velocidade, pressão e estruturas da turbulência) orientaram ajustes e melhorias
localizadas no projeto construtivo da alternativa tecnológica de limpeza online
proposta, permitindo eliminar zonas de recirculação e uma redução de 62,2 por cento nas
perdas de carga localizadas, que tão drasticamente impactam nos custos de
bombeamento do fluido de transporte dos artefatos de limpeza. A pressão simulada
reproduziu o resultado da medição com 2,5 por cento de concordância. Como conclusão, a
ferramenta computacional provou ser estratégica para orientar a melhoria do projeto
construtivo do dispositivo inovador de limpeza online. Se por um lado os dados
experimentais provêm uma referência confiável fundamentada em medições
rastreáveis a padrões de referência, por outro, a simulação numérica provê
relevantes informações em todo o domínio do escoamento. / [en] Heat exchangers are essential equipment in the cooling system of various
process equipment, aiming to ensure its effectiveness and operational efficiency.
The objective of the work is the computational simulation of the fluid flow
transporting cleaning artifacts from a technological alternative for heat exchangers
that does not require interruption of the industrial process. The motivation resulted
from the potential of the CFD computational tool to generate numerical results of
interest, complementing the experimental database in critical flow locations that are
difficult to instrument. The simulation was carried out by Fluent/Ansys 2023 R2,
using the κ-omega SST (Shear Stress Transport) turbulence model based on the
Reynolds average approach (RANS - Reynolds-Averaged Navier-Stokes). The
simulation results (velocity, pressure fields, and turbulence structures) guided
adjustments and localized improvements in the constructive design of the proposed
online cleaning technological alternative, allowing the elimination of recirculation
zones and a 62.2 percent reduction in localized pressure losses that so drastically impact
the costs of pumping the fluid to transport cleaning artifacts. The simulated pressure
reproduced the measurement results with 2.5 percent agreement. In conclusion, the
computational tool proved to be strategic in guiding the improvement of the
constructive design of the innovative online cleaning device. If, on the one hand,
experimental data provides a reliable reference based on measurements traceable to
reference standards, numerical simulation provides relevant information across the
entire flow domain.
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