Publications

Wall slip effects in a rheometer with double concentric cylinder geometry may lead to significant errors in measurement of the apparent viscosity. Previously, we proposed to use a slotted rotor design to reduce these effects. In this paper, we conduct two- as well as three-dimensional computational fluid dynamics (CFD) simulations to determine the differences in rheological measurements of yield stress fluids between the slotted and non-slotted rotor designs. The test fluid and the slip wall boundary of a rotor are characterized in our computational model by the constitutive equation of Zhu et al. (2005) and the wall-slip length method, respectively. The model has been validated against the existing rheological data measured using a vane rheometer. The results of this study indicate that the rheometer equipped with a slotted rotor can measure the fluid properties with enhanced accuracy and less sensitivity to the wall slip velocity than a rheometer with a non-slotted rotor. We also show that the wall slip effects can be further reduced by either increasing the slot ratio or adding more slots to the rotor. This work illustrates that CFD analysis can be a powerful tool in rheometer design.

White blood cells (WBCs), also known as leukocytes, migrate to sites of infection to destroy pathogenic microorganisms. The ability of WBCs to deform is essential for this function but it is also an important determinant of healthy vasculature. This chapter analyzes the effects of leukocyte deformability on leukocyte–endothelial interactions, presents the evidence for the critical role of the cytoskeleton in bulk mechanical properties of leukocytes, summarizes recent advances in rheological measurements of leukocytes, and discusses pathologies associated with leukocyte activation and reduced deformability of these cells.