CRISIS OF THE LAMINAR FLOW OF A NON-NEWTONIAN LIQUID IN A PIPE

The laminar-turbulent transition of fl ows of Newtonian (viscous) and non-Newtonian liquids in pipes was investigated on the basis of the combined analysis of the generalized equation of the fi rst and second laws of thermodynamics for a simple system and the Darcy–Weisbach equation. It is shown that a reason for the crises of the laminar fl ows of such liquids in pipes is the disturbance of the balance between the positive entropy production and the negative entropy fl ow in them. An analysis of calculation and experimental data on the disturbance of the laminar fl ow of a non-Newtonian liquid in a pipe and the transformation of this fl ow into a turbulent fl ow has shown that the crises of a laminar fl ow of an elastoviscoplastic liquid in a pipe happens at a larger critical Reynolds number compared to that of a laminar fl ow of a viscoplastic liquid at one and the same values of the Hedstrom parameter
   
Author:  A. G. Potapov
Keywords:  laminar-turbulent transition, Newtonian and non-Newtonian liquids, entropy production, entropy fl ow
Page:  1462