Kenneth Kensey

Effects of the non-Newtonian viscosity of blood on flows in a diseased arterial vessel. Part 1: Steady flows.

Effects of the non-Newtonian viscosity of blood on a flow in a coronary arterial casting of man were studied numerically using a finite element method. Various constitutive models were examined to model the non-Newtonian viscosity of blood and their model constants were summarized. A method to incorporate the non-Newtonian viscosity of blood was introduced so that the viscosity could be calculated locally. The pressure drop, wall shear stress and velocity profiles for the case of blood viscosity were compared for the case of Newtonian viscosity (0.0345 poise). The effect of the non-Newtonian viscosity of blood on the overall pressure drop across the arterial casting was found to be significant at a flow of the Reynolds number of 100 or less. Also in the region of flow separation or recirculation, the non-Newtonian viscosity of blood yields larger wall shear stress than the Newtonian case. The origin of the non-Newtonian viscosity of blood was discussed in relation to the viscoelasticity and yield stress of blood.

A new scanning capillary tube viscometer

The present study introduces a new scanning capillary tube viscometer for measuring fluid viscosity continuously over a range of shear rates including a low shear regime. Using a charge-coupled device sensor array, one could measure the changes in fluid level in a rising tube h(t) from which viscosity and shear rate were mathematically calculated. The concept of the new scanning capillary tube viscometer was validated by measuring viscosities of Newtonian fluids and comparing the results with those obtained with reference data and a rotating viscometer. Furthermore, the present method overcomes one of the major drawbacks of the capillary tube viscometer, the inability to produce viscosity data in a low shear range, by extending the shear rate range as low as 5 s−1 for water and diluted glycerin solutions at room temperature.

A scanning dual-capillary-tube viscometer

The present study introduces the concept of a new scanning dual-capillary-tube viscometer (SDCV) for viscosity measurements of both Newtonian and non-Newtonian fluids, including whole blood, over a wide range of shear rates. The flow rate and pressure drop measurements that are usually required for the operation of a capillary-tube viscometer are replaced with two measurements of liquid-height variation with time. Using a charge-coupled device sensor array, one could measure the variation of fluid levels at each riser tube, h1(t) and h2(t), from which the test fluid viscosity was calculated. The feasibility and accuracy of the SDCV technique has been demonstrated for a standard-viscosity oil and for bovine blood by comparing results against established viscosity measurement techniques. A power-law viscosity model was used to correlate the data for the latter. The dual-capillary-tube viscometer extends the shear rate range as low as 0.1 s−1 for both the viscosity of mineral oil (9.9 cP at 25 °C) and bovine...