Modelling the flow behaviour of very shear-thinning liquids

• Published in: Chemical engineering science 2001-10, Vol.56 (19), p.5617-5623
• Main Authors: Roberts, G.P., Barnes, H.A., Carew, P.
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Flow models; Fluid dynamics; Fundamental areas of phenomenology (including applications); Non-newtonian fluid flows; Physics; Rheological measurements; Rheology; Shear-thinning; Techniques and apparatus
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/S0009-2509(01)00291-3

With the arrival of the latest controlled-stress rheometers, we are now able to measure the steady-state flow-curves of structured liquids over a very wide range of applied shear stress. For many such liquids, these flow-curves show novel forms, which are usually very shear-thinning in character. Here, we introduce a category of empirical mathematical models—which are either simplifications, or else elaborations of the well-known and often-used Cross and Ellis models—that describe the behaviour of such intensely shear-thinning structured liquids, which had hitherto been described only at high shear rates or shear stresses using a flow model with a ‘ yield stress’ parameter, e.g., Bingham, Casson or Herschel–Bulkley types. These new models describe the flow-curves, whether above or below any previously described ‘ yield stresses’. The new models are found to be applicable to a range of structured liquids of commercial interest ranging from drilling muds, through molten chocolate to non-aqueous, flocculated dispersions.