omar abozaid

Abstract

Coarctation of the aorta (CoA) is a widespread anomaly that occurs a lot in infants. CoA affects the human health. It causes hypertension, decrease in the amount of blood flow and heart failure. CoA is related to abnormal hemodynamics and certain blood flow patterns are noticed. Different surgical techniques are implemented in order to increase the amount of blood flow such resection end-to-end anastomosis, resection end-to-side anastomosis…etc. This research aims at identifying the effect of CoA on the flow pattern and quantification of the improvement after surgery through utilizing computational fluid dynamics (CFD) to solve flow fields in the aorta. CFD is applied on a real geometry of the aorta are obtained by computerized tomography (CT) scan for five pre and post-operative patients. The boundary conditions are derived from the phase contrast magnetic resonance imaging (PC-MRI). Then, grid independence and time sensitivity analysis are performed. Flow patterns are judged visually by comparing the contours of the streamlines, vortex core, pressure and the time averaged wall shear stress (TAWSS). In order to quantify the flow fields and the improvement as well, different flow variables are used such as Womersley number, Strouhal number and specific turbulent kinetic energy. The wall shear stress at peak systole and the amount of the blood flow in the direction of the vessel’s centerline are used as a measure of improvement. The results of the CFD showed that blood flow patterns are highly dependent on the geometry of the vessel. For a CoA, jet formulation then break up, backflow and chaotic behavior exists after the area of the disease. In addition, a high concentrated wall shear stress is around the area of the CoA. For post-op, the change of the area because of the surgery produced separation. For both pre and post-op, the angle between the velocity vector at the inlet and the centerline of the vessel resulted in a jet impingement and very high wall shear stress. On the other hand, the specific turbulence kinetic energy and the wall shear stress is higher after the surgery. Strouhal number in the descending aorta has decreased after the operation except for one patient. The amount of blood flow increased after the surgery. Blood flow in the downstream became attached to the vessel. Finally, the flow fields are sensitive to the turbulence model; however, they did not show significant dependence on the viscosity model. The turbulence effects cannot be neglected due to their significant contribution to the velocity field.

Department

Mechanical Engineering Department

Degree Name

MS in Mechanical Engineering

Graduation Date

2-1-2016

Submission Date

May 2017

First Advisor

elmorsi, mohamed

Committee Member 1

elgabry, lamyaa

Committee Member 2

abdelrasheed, mahmoud

Extent

97 p.

Document Type

Master's Thesis

Rights

The author retains all rights with regard to copyright. The author certifies that written permission from the owner(s) of third-party copyrighted matter included in the thesis, dissertation, paper, or record of study has been obtained. The author further certifies that IRB approval has been obtained for this thesis, or that IRB approval is not necessary for this thesis. Insofar as this thesis, dissertation, paper, or record of study is an educational record as defined in the Family Educational Rights and Privacy Act (FERPA) (20 USC 1232g), the author has granted consent to disclosure of it to anyone who requests a copy. The author has granted the American University in Cairo or its agents a non-exclusive license to archive this thesis, dissertation, paper, or record of study, and to make it accessible, in whole or in part, in all forms of media, now or hereafter known.

Institutional Review Board (IRB) Approval

Not necessary for this item

Comments

I would like to express my thanks for all who helped in making this study possible. My supervisors Dr. Elmorsi and Dr. El-Khodary, for their scientific support and guidance. Dr.-Ing. Heba Aguib and Magdi Yacoub Foundation (MYF), for their support in the medical area and providence of the data of the patients. Dr. Ryo Torii for sending the MatLab and FORTRAN codes used for mapping the boundary conditions from the PC-MRI. Engr. Amr Sami, Engr. Mohamed Osman, Engr. Mohamed Atef, Engr. Hani Mashaal and other people working in OPTUMATICS, for their technical advises.

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