Analysis of coupled problem between collapsible tube and pulsatile flow by means of computational mechanics

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The coupled problem between collapsible tube and flow in it was solved by means of computational mechanics to researeh fluid-dynamic cause of blood disease such as arteriosclerosis. The collapsible tube is a model of blood vessels. When the tube law is used, the coupled problem is formulated as one-dimensional problem in the axial-direction of the tube. The pulsatile flow in a blood vessel is modeled as an isolated pressure wave propagating in the collapsible tube by using the tube law. The calculated pressure waves agreed well with experimental results. A two-dimensional calculation method is proposed to obtain the tube law with high accuracy and a three-dinensional FEM calculation of largely deformed tube by buckhng was performed to check three-dimensional effects of the tube on the tube law. A three-dimensional pulsatile flow calculation in a tapered U-bend as a model of an aortic arch was performed by means of FEM. The wall was asswned to be rigid due to the fact that the aortic arch has high rigidity. The obtained velocity profiles in the cross-sections are compared to experinental results, and secondary flow in the cross-section is shown. A method for calculating pressure distribution in the axial-direction pf the collapsible tube which is deformed largely by buckling due to low pressure in the tube was proposed. The three-dimensional flow in the largely deformed tube was numerically simulated. The axial velocity profiles in cross-sections obtained in the calculation were compared with experinental results, and reasonable agreement between them was obtained. The secondary flow distribution in the cross-sections, shear rate distribution in the tube and wall shear stress distribution are calculated. It is shown that high wall shear stress region occurs around the center of the cross'section which is buckled in figure-8 shaped.