Viscosity of human blood: transition from Newtonian to non-Newtonian.

Abstract

Samples of normal human blood, collected in acid citrate dextrose and adjusted to a hematocrit of 40, were tested in a rotational viscometer at 37[degree]C over the range of shear rate [gamma] of 0.1-315 sec-1, and supplementary tests were carried out in a capillary viscometer to extend the shear rate to 2600 sec-1, corresponding to a shear stress [tau] of about 80 dynes/cm2. The shear stress [tau] and corresponding shear rate [gamma] , when plotted as [image] vs. [image] , were correlated by the following linear equations-shear rate range 0 to approximately 20 sec-1: [image] -(Casson equation); shear rate range 100 sec-1 and higher: [image] (Newtonian equation); wherein = ultimate Newtonian viscosity, poise, and y = yield stress, dynes/cm2. Transition from the 1st to the 2nd equation occurred over the shear rate range rate of 16-100 sec-1.