Thermally-driven flows in polymeric liquids

Lappa, Marcello; Hashmi, Saleem, ed. (2020) Thermally-driven flows in polymeric liquids. In: Reference Module in Materials Science and Materials Engineering. Elsevier, Oxford, 724–742. ISBN 9780128035818 (

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Within the vast array of problems related to the processing of plastic materials and polymeric liquids, the main focus of the present chapter is the illustration of the typical dynamics of thermally-driven flows in these fluids, i.e. ‘natural’ fluid motion induced by gravity or surface-tension effects. Experimental struggles with understanding the basic mechanisms of these fundamental types of convection in viscoelastic fluids have been mitigated over recent years by the development of relevant models and adequate numerical techniques. On the one hand, this progress has produced new fundamental knowledge; on the other hand, it has led to new questions, both general and system-specific (a relevant example being represented by the intriguing concept of “elastic turbulence”). This field continues to burgeon and bring surprises to this day. A synthetic review of the salient outcomes of past and recent studies is reported in this chapter (articulated in focused subsections) together with a critical discussion of some accompanying necessary definitions and paradigms used to reveal the intimate essence of these liquids. For the convenience of the reader, however, advanced formal discussions and mathematical arguments are stripped down to their essentials. In the same spirit, the use of jargon is kept at minimum and much of the available space is devoted to the description (both qualitative and quantitative) of the considered convective phenomena, the related thresholds in terms of characteristic numbers and the underlying “physics”.