Numerical investigation of non-Newtonian fluid flow in channels with local expansion

Fluids can be classified from different perspectives. From the perspective of fluid behavior under the influence of shear stress, the fluids can be classified into Newtonian and non-Newtonian fluids. Newtonian fluid is a material in which shear stress without yield stress (at zero shear rate is zero shear stress) is only a linear function of shear rate and in this material shear stress to shear rate is called viscosity. In non-Newtonian fluids one of the two Newtonian fluid conditions (zero yield stress condition or shear stress linearity condition in terms of shear rate) or both conditions are not met simultaneously. In other words, it can be said that a non-Newtonian fluid is a fluid in which either the shear stress diagram is nonlinear in shear rate or if the diagram is linear it does not cross the origin of the coordinates.In this study, the study of non-Newtonian fluid flow in a rectangular cross-section channel for sudden discontinuity is investigated. The expansion coefficient is assumed to be 3 and the fluid flow is investigated in two-dimensional steady state. For numerical simulation, Poly flow commercial software, which is a subset of Ennis software, is used specifically to simulate non-Newtonian fluids. For different Reynolds, Weissenberg and Beta numbers, the vortex length has been measured in different conditions and the influence of the mentioned parameters on the vortex length has been investigated. Finally, contours of the flow lines are presented to determine the vortex length using them. It should be noted that the non-Newtonian fluid discussed in this study was selected from the type of oldroyd B fluid.

Keywords:

Local Expansion , Non-Newtonian Fluid , Numerical Simulation , Poly flow Software.