Plenary Lecture
Non-Monotonous Behaviour of Shear Viscosity - Empirical Modelling
Professor Petr Filip
Institute of Hydrodynamics
Academy of Science
Czech Republic
E-mail: filip@ih.cas.cz
Abstract: Practically all hitherto used empirical models used for characterisation of shear viscosity of liquids describe only its monotonous course. However, the onset of new materials is accompanied by more complicated characteristics of their behaviour including non-monotonous course of shear viscosity. This feature reflects not only in an existence of one extreme point (maximum or minimum) but there can appear both extreme points; i.e. that shear viscosity initially exhibits shear thinning, after attaining a local minimum converts to shear thickening, and again after reaching a local maximum has a shear-thinning character. It is clear that for an empirical description of this complex behaviour a hitherto used number of parameters (four, five) in classical monotonous models (such as Cross or Carreau-Yasuda) are no longer tenable. If more parameters are applied, there should be given an emphasis on a relatively simple algebraic form of the proposed models, unambiguity of the involved parameters and their sound interpretation in the whole modelling. This contribution provides an overview of the existing non-monotonous models and proposes a new 10-parameter model including a demonstration of its flexibility using various experimental data.
Brief Biography of the Speaker: Petr Filip graduated from the Charles University in Prague, Faculty of Mathematics and Physics, Czech Republic in 1976. He completed his Ph.D. study at the Institute of Mathematics, Acad. Sci. Czech Rep., his Ph.D. Thesis was devoted to oscillatory solutions of partial differential equations. Since 1980 he has been with the Institute of Hydrodynamics, Acad. Sci. Czech Rep., Prague, for many years as a head of the Department of Chemical Engineering where he was interested in fluid mechanics, especially theory of jets and mixing. Later on he was appointed to the position of a scientific secretary (up to now), at present his sphere of interest is rheology (flow of non-Newtonian liquids). He is an author (co-author) of more than 100 contributions published in international journals and conference proceedings.