Blood viscosity at different shear rates in capillary tubes

Abstract

Blood flow through tubes is best described by the Casson equation in the shear rate range 15–6400 sec⁻¹, i.e. ${\mathit{\tau }}^{1\mathrm{/}2}={\mathit{k}}_0+{\mathit{k}}_1{\dot{\mathit{\gamma }}}^{1\mathrm{/}2}$ , where τ is shear stress, $\dot{\mathit{\gamma }}$ is shear rate, k ₀ and k ₁, are not true constants but vary slowly with shear rate. This equation implies that viscosity coefficient, calculated in the usual manner, will vary with tube diameter and pressure gradient. It is shown that yield shear stress is not important physiologically.