EFFECT OF NONAXISYMMETRIC HEMATOCRIT DISTRIBUTION ON NON-NEWTONIAN BLOOD-FLOW IN SMALL TUBES

Hematocrit distribution and red blood cell aggregation are the major d eterminants of blood flow in narrow tubes at low flow rates. It has be en observed experimentally that in microcirculation the hematocrit dis tribution is not uniform. This nonuniformity may result from plasma sk imming and cell screening effects and also from red cell sedimentation . The goal of the present study is to understand the effect of nonaxis ymmetric hematocrit distribution on the flow of human and cat blood in small blood vessels of the microcirculation. Blood vessels are modele d as circular cylindrical tubes. Human blood is described by Quemada's rheological moder, in which local viscosity is a function of both the local hematocrit and a structural parameter that is related to the si ze of red blood cell aggregates. Cat blood is described by Casson's mo del. Eccentric hematocrit distribution is considered such that the axi s of the cylindrical core region of red cell suspension is parallel to the axis of the blood vessel but not coincident. The problem is solve d numerically by using finite element method. The calculations predict nonaxisymmetric distribution of velocity and shear stress in the bloo d vessel and the increase of apparent viscosity with increasing eccent ricity of the core. (C) 1998 Elsevier Science Ltd.