Abstract
The methods normally employed for shear rate calculations from concentric cylinder viscometer data generally are not applicable for fluids with a yield stress. In cylindrical systems with large radius ratios, as usually is the case with suspensions, the yield stress induces two possible flow regimes in the annulus. Unless the yield value is exceeded everywhere in the gap only part of the fluid can be sheared while the remaining region behaves like a solid plug. A correct calculation of the shear rate must take into account the presence of a variable effective gap width determined by the extent of the sheared layer. For time-independent yield stress fluids, a two-step procedure, which does not require any specific flow model, is proposed for analysing the experimental torque-speed data. Under the partially sheared condition, the shear rate can be computed exactly, whereas for the fully sheared flow the Krieger and Elrod approximation is satisfactory. The method is assessed by examining both semi-ideal data generated with a Casson fluid with known properties, and experimental data with an industrial suspension. A more complicated problem associated with characterization of time-dependent yield stress fluids is also identified and discussed. An approximate procedure is used to illustrate the dependence of the shear rate on time of shear in constant-speed experiments.
Similar content being viewed by others
References
Van Wazer JR, Lyons JW, Kim KY, Colwell RE (1963) Viscosity and Flow Measurement. Interscience, New York, p 47
Skelland AHP (1967) Non-Newtonian Flow and Heat Transfer. Wiley, New York
Yang TMT, Krieger IM (1978) J Rheol 22:413
Darby R (1985) J Rheol 29:369
Krieger IM, Elrod H (1953) J Appl Phys 24:134
Krieger IM, Maron SH (1954) J Appl Phys 25:72
Krieger IM (1968) Trans Soc Rheol 12:5
Nguyen QD, Boger DV (1983) J Rheol 27:321
Nguyen QD, Boger DV (1985) J Rheol 29:335
Nguyen QD, Boger DV (1985) Rheol Acta 24:427
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Nguyen, Q.D., Boger, D.V. Characterization of yield stress fluids with concentric cylinder viscometers. Rheol Acta 26, 508–515 (1987). https://doi.org/10.1007/BF01333734
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF01333734