| Popis: |
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. |
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