Rheologically complex liquids

Abstract This chapter deals with capillary instability of straight free liquid jets moving in air. It begins with linear stability theory for small perturbations of Newtonian liquid jets and discusses the unstable modes, characteristic growth rates, temporal and spatial instabilities and their underlying physical mechanisms. The linear theory also provides an estimate of the main droplet size emerging from capillary breakup. Formation of satellite modes is treated in the framework of either asymptotic methods or direct numerical simulations. Then, such additional effects like thermocapiUarity, or swirl are taken into account. In addition, quasi-one-dimensional approach for description of capillary breakup is introduced and illustrated in detail for Newtonian and rheologically complex liquid jets (pseudoplastic, dilatant, and viscoelastic polymeric liquids). 

Keywords Capillary instability of liquid jets Curvature Elongational rheology Free liquid jets Linear stability theory Nonlinear theory Quasi-one-dimensional equations Reynolds number Rheologically complex liquids (pseudoplastic, dilatant, and viscoelastic polymeric liquids) Satellite drops Small perturbations Spatial instability Surface tension Swirl Temporal instability Thermocapillarity Viscosity... 

Capillary Breakup of Rheologically Complex Liquid Jets... 

Keywords Bending instability of liquid jets Buckling of liquid jets Electrified liquid jets Electrospinning Elongational rheology Newtonian and rheologically complex liquids Quasi-one-dimensional equations of the dynamics of liquid jets Small and finite perturbations Viscoelastic polymeric liquids... 

CapUlaiy instability and breakup of thin jets of dilute polymer solutions considered in section CapUlaiy Breakup of Rheologically Complex Liquid Jets of Chap. 1 represents itself an example of the so-called strong flows, in which coil-stretch transitiOTi of macromolecular coils can happen because the elongation rate is so... 

In this chapter, we have attempted to provide a critical appraisal of the current status of bubble dynamics in rheologically complex liquids. In free... 

Complex liquids seldom behave as classical Newtonian fluids thus, analysis of their behavior requires a thorough understanding of non-Newtonian rheology. The importance of this knowledge is illustrated by the following two examples ... 

The theoretical basis for spatially resolved rheological measurements rests with the traditional theory of viscometric flows [2, 5, 6]. Such flows are kinematically equivalent to unidirectional steady simple shearing flow between two parallel plates. For a general complex liquid, three functions are necessary to describe the properties of the material fully two normal stress functions, Nj and N2 and one shear stress function, a. All three of these depend upon the shear rate. In general, the functional form of this dependency is not known a priori. However, there are many accepted models that can be used to approximate the behavior, one of which is the power-law model described above. 

Clearly, the response of fluids to an applied shear can be linear or nonlinear and depends on two major factors shear rate and structural or mechanical properties of the system, which in turn depend upon the interaction between the components including the rheological additives. It is the latter that primarily determines the flow properties of LADDs. The intent of this section is to discuss various rheological properties and test methods pertinent to LADDs. Interested readers are referred to Chapter 4, which deals with the rheology of complex liquids and suspensions, and other books [76-79] and review articles [80-82] covering this subject. Heywood [83] discusses the criteria for selecting various commercial viscometers. 

Can it be applied to fluids with complex rheology or different atomization modes Unknown. Unclear whether it would be possible to formulate the appropriate constraints for complex liquids Yes Yes... 

Larson RG (2000) Structure and rheology of complex liquids. Oxford University Press, New York... 

Iliuta I, Larachi F. Hydrodynamic models for rheologically complex fluids in co- and countercurrent gas-liquid packed-bed bioreactors. Ind. Eng. Chem. Res. 2002b 41 2096. 

The rheology of liquid crystals is more complex than for ordinary liquids. The anisotropy of the liquid... 

Investigation on the Usage of Effervescent Atomization for Spraying and Spray Drying of Rheological Complex Food Liquids and on the... 

In most of the complex liquids described here, the stmctures developed in the liquids and their rheological properties are generally very sensitive to the thermal and mechanical histories imposed on the liquids. Therefore, it is most desirable to conduct truly simultaneous measurements of the various properties and stmctures in situ for a given complex liquid in order to avoid complications brought by effects such as the various measured quantities of the liquid reflecting different states due to different thermal and/or mechanical histories. 

Rheology is the science that deals with the deformation and flow of matter under various conditions. The rheology of plastics, particularly of TPs, is complex but understandable and manageable. These materials exhibit properties that combine those of an ideal viscous liquid (with pure shear deformations) with those of an ideal elastic solid (with pure elastic deformation). Thus, plastics are said to be viscoelastic. 

Rheology deals with the deformation and flow of any material under the influence of an applied stress. In practical apphcations, it is related with flow, transport, and handling any simple and complex fluids [1], It deals with a variety of materials from elastic Hookean solids to viscous Newtonian liquid. In general, rheology is concerned with the deformation of solid materials including metals, plastics, and mbbers, and hquids such as polymer melts, slurries, and polymer solutions. 

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