Comparative examination of constitutive equations for apparent viscosity of human blood

ABSTRACT

The adequate mechanical characterization of blood is an important prerequisite for quantitative description of blood flow. Variation in the apparent viscosity among normal is very small. Thus, changes due to disease or surgical intervention can be readily identified, making blood viscosity a useful clinical parameter. So, to understand many aspects of the cardiovascular system in physiological and pathological states many models studied the apparent viscosity of human blood. Consequently, it is necessary to select a constitutive equation suitable for numerical analysis to compare computed values with experimental data of blood viscosity. In the present work, three constitutive equations namely, corotational Jeffreys, Oldroyed 8-constant and Giesekus models, were studied by comparing computed values with the experimental data of the blood viscosity. To this end, accurate point viscosity data previously obtained by Brookfield DV-III Rheometer is utilized. For each constitutive equation, the numerical values of constants which yield the best fit with experimental data are determined. The best agreement between experimental and calculated viscosity is obtained with the Giesekus model. The success of this model is attributed to the deformation rate dependence of its viscosity and time constants