Influence Of non-Newtonian Behavior Research Articles

Influence of Non-Newtonian Behaviour on the Processing Characteristics of Wall-slipping Materials

Abstract So far it has been assumed that when describing the flow process in single-screw extruder, the melt will be wall-adhering. Using certain process conditions, however, some materials such as PVCs, high-molecular PEs, elastomers, polymer suspensions, ceramic materials and food products become wall-slipping [1 to 4]. During simulation of the flow process using the Finite Element Method (FEM), the boundary condition of “wall-adhering” was substituted for “wall-slipping”. The numeric results refer to one-dimensional, non-Newtonian, isothermal flow processes and have been evaluated accordingly. Since the wall-slipping properties are dependent on critical shear stress, the influence of non-Newtonian behaviour on wall shear stress is illustrated by investigating the barrel and screw root surface. Conclusions with regard to wall-slipping properties may be drawn from the resulting upper and lower limits. The effect of wall slippage on pressure/throughput behaviour is examined along with the various velocity profiles, resulting from different compression ratios, dimensionless critical shear stress, material-related constants and screw configuration.

Peristaltic transport of a power-law fluid: Application to the ductus efferentes of the reproductive tract

The problem of peristaltic transport of a non-Newtonian (power-law) fluid in uniform and non-uniform two-dimensional channels has been investigated under zero Reynolds number with long wavelength approximation. A comparison of the results with those for a Newtonian fluid model shows that the magnitude of pressure rise, under a given set of conditions, is smaller in the case of the non-Newtonian fluid (power-law indexn < 1) at zero flow rate. Further, the pressure rise is smaller asn decreases from 1 at zero flow rate, is independent ofn at a certain value of flow rate and becomes greater if flow rate increases further. Also, at a given flow rate, an increase in wavelength leads to a decrease in pressure rise and increase in the influence of non-Newtonian behaviour. Pressure rise in the case of non-uniform geometry, is found to be much smaller than the corresponding value in the case of uniform geometry. Finally, the analysis is applied and compared with observed flow rates in the ductus efferentes of the male reproductive tract.