STEADY VISCOUS-FLOW IN CONSTRICTED ELASTIC TUBES SUBJECTED TO A UNIFORM EXTERNAL-PRESSURE

Cardiovascular illness is most commonly caused by a constriction, call ed a stenosis. A non-linear mathematical model with a free moving boun dary was introduced to study viscous flow in tapered elastic tubes wit h axisymmetric constrictions subject to a prescribed pressure drop and a uniform external pressure. An iterative numerical scheme using a bo undary iteration method was developed to solve the model. Effects of s tenosis severity and stiffness, pressure drop, external pressure and s tiffness of the vessel wall on the flow and wall motion were evaluated . It was found that stenosis severity, pressure drop and external pres sure played more dominant roles than tube wall stiffness and stenosis stiffness perturbation. Tubes with 71 and 78 per cent stenoses showed two areas of negative transmural pressure and complex contraction-expa nsion-contraction wall motion patterns. Two types of tube diameter con traction and negative transmural pressure were observed, one was just distal to the stenosis and the other was near the outlet of the tube. Experiments using stenotic silicone tubes were conducted to quantify t he tube law and verify the predicted pressure-flow relationship. The a greement between the numerical results and experimental measurements i s better than that from a previous model which assumed periodicity of the tube and imposed different pressure conditions. (C) 1998 John Wile y & Sons, Ltd.