A new laminar-to-turbulent transition criterion for yield-pseudoplastic fluids

A new laminar-to-turbulent transition criterion for predicting the onset of turbulence for yield-pseudoplastic fluids was developed. This criterion is defined as the ratio of the laminar shear stress to the viscous shear stress. The value of the ratio is equal to unity in the viscous sublayer and should be greater than unity in the turbulent zone. The rheological characteristics of the fluids studied were described by a power-law yield-pseudoplastic model. Two equations relating the Metzner and Reed parameters (n' and k') to those of yield-pseudoplastic model ( tau(y), mu(p), and n) were derived. The developed criterion can also be used to determine the onset of turbulent flow for Bingham and yield-dilatant fluids. (C) 1998 Elsevier Science B.V.