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Water hammer experiment in artificial blood vessel
Hromádka, D. ; Horný, L. ; Žitný, R. ; Chlup, Hynek
This paper presents a water hammer experiment performed on an artificial blood vessel and the latex tube. Artificial blood vessel was manufactured from latex tubes and textile rubber bands. These bands were wound on outer surface of latex tube and they imitated reinforcing effect of collagen fibres. Mathematical model describes pulsation of pressure after instantaneous closing of valve at outlet of pipeline a part of which is a short elastic tested tube. It is shown that the observed pressure responses can be approximated by a simplified mathematical model assuming linear relationship between internal pressure and inflated volume.
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Residual Strains of Arteries as Forensic Index
Adámek, T. ; Horný, L. ; Chlup, Hynek ; Žitný, R.
It has been known for long time that arteries are pre-strained in situ. These residual strains play crucial role in arterial load-bearing capacity. However, to the best of authors’ knowledge they have never been considered from forensics point of view. This paper concerns a possibility of employing the longitudinal pre-strain of human aortas as an indicator of human subject age. Lengths of abdominal aorta were measured within autopsies before and after segment resection. Longitudinal stretch ratio was calculated for 45 male and 12 female cadavers. It was found that both male and female data samples give approximately the same mean of the stretch ratio = 1.2. The correlation coefficients between the pre-strain and age were R=-0.7926, R=-0.8684 in male and female samples, respectively. Linear regression equation with confidence intervals was employed. The correlation between pre-strain and age seems to be suitable statistics to be used in forensic sciences.
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Numerical Simulation and Experimental Modelling of Fluid - Structure Interaction in Veins
Štembera, V. ; Chlup, Hynek ; Maršík, František
The mixed formulation of the finite element method with the separately interpolated pressure is used for the numerical simulation of the fluid structure interaction. To describe a wider class of problems we consider in the simulation the three material models: the Neo-Hookean, the isotropic Gent model and the anisotropic Gent material model to include the influence of collagen structure of blood vessels. The fluid is modelled as Newtonian liquid. The strong coupling of both structure and fluid solvers allow us to simulate large deflection oscillations of the structure. The special experimental mock up line was designed for the investigation of unsteady fluid structure phenomena. Latex tubes with variable inner diameter and wall thickness are used as specimens. The qualitative and quantitative fluid structure phenomenon investigation are performed for both the continuous and pulsatile flow.
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The Conditions of Vibrations and Collapse of Human Blood Vessels
Hemza, J. ; Chlup, Hynek ; Maršík, František
Biomechanical material properties of arteries and veins are investigated experimentally and theoretically. The main goal of the histological research and the developed theory is to formulate the biomechanical conditions (geometrical dimensions, viskoelastic properties of veins and blood fluid flow conditions) at which an unstable behavior or even the vein collapse can occur. One dimensional fluid structure approximation was starting point for the theoretical analysis of fluid flow through highly elastic collapsible tube. Provided that the neo-Hook’s material model was applied the analytical formula for the collapse conditions was found. It was proved that for the brain vein contraction about 5%, the vein collapse can occurs even under normal physiological condition into vessels – the angiosynizesis. The fluid structure interaction is studied experimentally on the special experimental line. Latex tubes with variable inner diameter and wall thickness are used as specimens.
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