The in#uence of the non-Newtonian properties of blood on the #ow in large arteries: unsteady #ow in a 903 curved tube

A numerical and experimental investigation of unsteady entry #ow in a 903 curved tube is presented to study the impact of the non-Newtonian properties of blood on the velocity distribution. The time-dependent #ow rate for the Newtonian and the non-Newtonian blood analog #uid were identical. For the numerical computation, a Carreau}Yasuda model was employed to accommodate the shear thinning behavior of the Xanthan gum solution. The viscoelastic properties were not taken into account. The experimental results indicate that signi"cant di!erences between the Newtonian and non-Newtonian #uid are present. The numerical results for both the Newtonian and the non-Newtonian #uid agree well with the experimental results. Since viscoelasticity was not included in the numerical code, shear thinning behavior of the blood analog #uid seems to be the dominant non-Newtonian property, even under unsteady #ow conditions. Finally, a comparison between the non-Newtonian #uid model and a Newtonian #uid at a rescaled Reynolds number is presented. The rescaled Reynolds number, based on a characteristic rather than the high-shear rate viscosity of the Xanthan gum solution, was about three times as low as the original Reynolds number. Comparison reveals that the character of #ow of the non-Newtonian #uid is simulated quite well by using the appropriate Reynolds number. ( 1999 Elsevier Science Ltd. All rights reserved