A method of isolating surface tension and yield stress effects in a U-shaped scanning capillary-tube viscometer using a Casson model

The present study introduces a method to consider different surface tensions at two riser tubes for the viscosity measurements of fluids using a U-shaped scanning capillary-tube viscometer (SCTV). The accuracy and repeatability of the SCTV were demonstrated by comparing the viscosity results of distilled water obtained from the SCTV with the well-accepted reference data for water. Non-Newtonian viscosities of bovine blood containing 7.5% ethylenediaminetetraacetic acid (EDTA) and fresh human blood were measured at 25 degreesC and at a body temperature of 37 C, respectively. The viscosity results for bovine blood gave excellent agreement with the results obtained from a rotating viscometer. The results demonstrate that whole blood viscosity can be measured over a range of shear-rates in less than 2-3 min without any anticoagulants using disposable U-shaped capillary-tube sets. (C) 2002 Elsevier Science B.V. All rights reserved.