ISSN:
1435-1528
Keywords:
Flow stability
;
Couette flow
;
Taylor vortices
;
power law viscosity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Abstract The stability of the Couette flow of the liquid with the power law viscosity in a wide annular gap has been investigated theoretically in this work with the aid of the method of small disturbances. The Taylor number, being a criterion of the stability, has been defined using the mean apparent viscosity value in the main flow. In the whole range of the radius ratio, R i /R o and the flow index, n, considered (R i /R o ≥ 0.5, n = 0.25–1.75 ), the critical value of the Taylor number Ta c is an increasing function of the flow index, i.e., shear thinning has destabilizing influence on the rotational flow, and dilatancy exhibits an opposite tendency. In the wide ranges of the flow index, n 〉 0.5, and the radius ratio, R i /R o 〉 0.5, the wide-gap effect on the stability limit is predicted to be almost the same for non-Newtonian fluids as for Newtonian ones. The ratio on the critical Taylor numbers for non-Newtonian and Newtonian fluids: Ta c (n) and Ta c (n = 1) obey a generalized functional dependence: Ta c (n)/Ta c (n = 1) = g(n), where g(n) is a function corresponding to the solution for the narrow gap approximation. Theoretical predictions have been compared with experimental results for pseudoplastic liquids. In the range of the radius ratio R i /R o 〉 0.6 the theoretical stability limit is in good agreement with the experiments, however, for R i /R o 〈 0.6, the critical Taylor number is considerably lower than predicted by theory.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00366505
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