Hemodynamic parameters on the macromolecular transport between serum and blood vessel wall

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1. Pulsatile Flow and wall stress in Models of the Abdominal Aortic Aneurysm: Pulsatile Flows in glass models simu-lating fusiform and lateral saccular aneurysms were investigated by a flow visualization method. At the initial stage of accelerating phase, the flow began to separate from the proximal wall of the aneurysm. Then the saparate bubble or vortex grew rapidly in size and filled the whole area of the aneurysm circumferentially. During this period of time, the center of the vortex moved from the proximal end to the distal point of the aneurysm. The transient reversal flow, for instance, which may occur at the end of the ejection period, passed between the wall of the aneurysm and the centrally located vortex. When the rate and pulsatile frequency of flow were high, the vortex broke down into turbulence at the distal portion of aneurysm. The same effect was observed when the length of the aneurysm was increased. A re-duction in pulsatile amplitude made the flow pattern close to t … More hat in steady flow. A finite element analysis was made to obtain velocity and pressure fields in pulsatile flow through a tube with an axisymmetric expansion. Caluculated in stantaneous patters of velocity field and stream lines agreed well with the experimental results. The appearance and disapperance of the vortex in the dilated portion and its development resulted in complex distributions of pressure and shear fields. Locally minimum and maximum values of wall shear stress occured at points just upstream and down stream of the distal end of the expansion when the flow rate reached ist peak. Wall stress distribution was investigated nu-merically as the result of loading wall shear stress and pressure on inner wall of the aneurysm model. It was depended upon presuure than wall shear stresss loading. The shear stress concentration in the wall was generated between middle and distal portion of the aneurysm.2. Pulsatile Flow Through the Human Carotid Arteries: Visualization experiments were performed to elucidate the complicated flow pattern in pulsatile flow thorugh the human carotid arteries which were made transparent. Helically recirculating flow with a pattern similar to that of the horseshoe vortex produced around wall-based protuberances in circular tubes was observed in pulsatile flow through all the bifurcations used in the present study. The horseshoe vortex has also been demonstrated to occure at the human common carotid bifurcation in steady flow with reynolds number above 100. Time-varying flows also produced the horseshoe vortex mostly during the decelerating phase. While this helical flow was produced, the stagnation points appeared on the wall upstream of the apex. Their position was dependent upon the flow distribution ratio between braches in the individual arteries. A separation bubble was observed at the outer or inner wall of the branch vessels.3. Stress analysis in the wall perpendicular to tube axis was performed at arterial branch site. Tension and compressionwere seen at the inner and outer wall on the line of apsides. The more attension toward quantiating the relationship between the mechanical properties of the vessel wall and arterial disease is disired in the future study. Less