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Analysis of residual stresses in arterial wall
Novák, Kamil ; Fuis, Vladimír (referee) ; Burša, Jiří (advisor)
This thesis deals with computational modeling of the influence of residual stresses in idealized geometry of blood vessels and subsequent application of acquired knowledge to abdominal aortic aneurysm. In the terms of quality of the computational model, we reduced the uncertainties that are included in the computational model without considering the influence of residual stresses. The basic assumption of homogenization significant peaks of the stress between inner and outer vessel wall was met for each level of the computational model Methods that have been used are: deformation method (opening angle method), inverse mechanics of large deformations, fictitious temperature – for linear elastic material and hyperelastic material defined by the constitutive model. Numerical verification was carried out using program ANSYS.
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Computational modelling of stresses in intracranial aneurysms
Turčanová, Michaela ; Polzer, Stanislav (referee) ; Burša, Jiří (advisor)
The diploma thesis deals with the assessment of the prediction of brain aneurysm rupture based on its geometrical and material properties. In the first part of the thesis there is a~detailed research study of cardiovascular systems with a focus on the cerebral artery and aneurysm occurring on their bifurcates. The second part of the thesis is focused on the creation of two models of arterial cerebral bifurcation with the presence of aneurysm and on obtaining their geometry in unloaded state. Emphasis is placed on the most realistic constitutive model of the artery wall material based on real data from uniaxial tensile tests and on a suitably chosen blood pressure load. This blood pressure may be step-changed, for example, in bungee jumping. In the work, a calculation of the increase in blood pressure during the step-change is performed, which is subsequently used in calculations of tension in the wall of the cerebral aneurysm. In conclusion, the risk of rupture is evaluated in two model idealized brain aneurysms and a discussion of the credibility of the results is given.
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The interaction of non-newtonian fluids with a flexible wall
Šedivý, Dominik ; Drábková, Sylva (referee) ; Šidlof,, Petr (referee) ; Fialová, Simona (advisor)
The doctoral thesis deals with an interaction between non-newtonian fluid and flexible wall. This interaction occurs continuously in all human bodies since a blood is a non-newtonian fluid and blood vessels belong to hyperelastic materials. The main aim of the thesis was to study and evaluate the impact of non-newtonian fluid on the flow. The aorta is blood vessel with the highest deformations and flowrates and it was studied in this work. The practical section of thesis is divided into two parts. Experimental measurements are contained in the first part and numerical simulations are in the second part. A new testing device was designed and built. Measurements were done for both types of fluid (newtonian and non-newtonian) and with two types of tubes. One of them was made from glass and was considered as rigid. The second one was pliable and it was made from silicon. Measurement outputs were velocity profiles (measured by PIV), pliable tube deformations and absolute pressures at the inlet and the outlet of the tubes. Simulations were based on experimental data and were performed in software ANSYS. The simulation of the flow in the pipe with rigid wall was calculated with computational fluid dynamic. Fluid-structure interaction was applied in case of pliable tube, therefor structural solver was coupled with CFD solver. Simulations were used for evaluation of physical quantitie which were not possible to measure. Simple mathematical model was created based on the results.
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Computational modelling of stresses in intracranial aneurysms
Turčanová, Michaela ; Polzer, Stanislav (referee) ; Burša, Jiří (advisor)
The diploma thesis deals with the assessment of the prediction of brain aneurysm rupture based on its geometrical and material properties. In the first part of the thesis there is a~detailed research study of cardiovascular systems with a focus on the cerebral artery and aneurysm occurring on their bifurcates. The second part of the thesis is focused on the creation of two models of arterial cerebral bifurcation with the presence of aneurysm and on obtaining their geometry in unloaded state. Emphasis is placed on the most realistic constitutive model of the artery wall material based on real data from uniaxial tensile tests and on a suitably chosen blood pressure load. This blood pressure may be step-changed, for example, in bungee jumping. In the work, a calculation of the increase in blood pressure during the step-change is performed, which is subsequently used in calculations of tension in the wall of the cerebral aneurysm. In conclusion, the risk of rupture is evaluated in two model idealized brain aneurysms and a discussion of the credibility of the results is given.
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Analysis of residual stresses in arterial wall
Novák, Kamil ; Fuis, Vladimír (referee) ; Burša, Jiří (advisor)
This thesis deals with computational modeling of the influence of residual stresses in idealized geometry of blood vessels and subsequent application of acquired knowledge to abdominal aortic aneurysm. In the terms of quality of the computational model, we reduced the uncertainties that are included in the computational model without considering the influence of residual stresses. The basic assumption of homogenization significant peaks of the stress between inner and outer vessel wall was met for each level of the computational model Methods that have been used are: deformation method (opening angle method), inverse mechanics of large deformations, fictitious temperature – for linear elastic material and hyperelastic material defined by the constitutive model. Numerical verification was carried out using program ANSYS.
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