ISSN:
1435-1528
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Summary Measurements of the viscometric properties of a thixotropic fuel oil at constant shear rate have shown a reduction of viscosity that has the characteristics of combined long term and short term exponential decay processes. It is possible to evaluate parameters from experimental data for decay processes which combine to represent the observed time dependence of viscosity. At a particular shear rate the time dependence can be represented as: $$\begin{gathered} \mu (t) = \mu _0 - \Delta \mu _1 (1 - e^{{{ - t} \mathord{\left/ {\vphantom {{ - t} {\lambda _1 }}} \right. \kern-\nulldelimiterspace} {\lambda _1 }}} ) \hfill \\ - \Delta \mu _2 (1 - e^{{{ - t} \mathord{\left/ {\vphantom {{ - t} {\lambda _1 }}} \right. \kern-\nulldelimiterspace} {\lambda _1 }}} ) \hfill \\ \end{gathered} $$ . When measurements are made for a range of shear rates it is found that the time constants,λ 1 andλ 2, are relatively unchanged while the viscosity deficits,Δµ 1 andΔµ 2, and the initial viscosity are shear rate dependent. For a limited shear rate range the nature of this dependency can be expressed as: $$\begin{gathered} \Delta \mu (\dot \gamma ) = \Delta \mu ^1 \dot \gamma ^n \hfill \\ \mu _0 (\dot \gamma ) = \mu _0^1 \dot \gamma ^{n_0 } \hfill \\ \end{gathered} $$ whereΔμ 1 andµ 0 1 are evaluated at $$\dot \gamma = 1$$ and the various indices all lie between 0 and −1. The time dependence of viscosity measured at constant shear rate can then be represented as: $$\begin{gathered} \mu (t) = \mu _0^1 \dot \gamma ^{n_0 } - \Delta \mu _1^1 \dot \gamma ^{n_1 } (1 - e^{{{ - t} \mathord{\left/ {\vphantom {{ - t} {\lambda _1 }}} \right. \kern-\nulldelimiterspace} {\lambda _1 }}} ) \hfill \\ - \Delta \mu _2^1 \dot \gamma ^{n_2 } (1 - e^{{{ - t} \mathord{\left/ {\vphantom {{ - t} {\lambda _2 }}} \right. \kern-\nulldelimiterspace} {\lambda _2 }}} ). \hfill \\ \end{gathered} $$ With this characterization method long term, short term, time independent and shear rate dependent characteristics of a material can be individually identified.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01525594
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