Non-Newtonian fluids with a yield stress

A modified Herschel-Bulkley model [E. Mitsoulis, S.S. Abdali, Flow simulation of Herschel-Bulkley fluids through extrusion dies, Can. J. Chem. Eng. 71 (1993) 147-160] predicts an infinite apparent viscosity at vanishing shear rate. Furthermore, the dimensions of one parameter depend on another parameter. In this contribution, we propose a generalized model based on earlier work by De Kee and Turcotte [D. De Kee, G. Turcotte, Viscosity of biomaterials. Chem. Eng. Commun. 6 (1980) 273-282] and on the work of Papanastasiou [T.C. Papanastasiou, Flows of materials with yield, J. Rheol. 31 (1987) 385-404] to solve the problems associated with the modified Herschel-Bulkley model. Compared to the responses of the Papanastasiou model and the modified Herschel-Bulkley model, the proposed generalized model provides the expected improvements and is capable of predicting successfully the rheological behavior (viscosity and yield stress) of Carbopol 980 dispersions.