Yousef Tamsilian - Sharif University of Technology Petroleum and Chemical Engineering Department Tehran, Iran.
Amirhosein Ahmadian - Sharif University of Technology Petroleum and Chemical Engineering Department Tehran, Iran.
Ahmad Ramazani s.a - Sharif University of Technology Petroleum and Chemical Engineering Department Tehran, Iran.

This study presents CFD modeling of Newtonian, generalized-Newtonian and viscoelastic fluidflows in an extruder concerning screw turning (as realistic boundary) and barrel turning (as classical boundary) to compare modern extrusion modeling vs. classical extrusion modeling in which normally barrel turns.A three dimensional finite-volume scheme is used to solve momentum and fluid constitutive equations by a generated hex grid for the convective-type terms to discrete the equations and solve the set of governing equations. The simulations concern incompressible fluids obeying different constitutive equations: Newtonian fluid, generalized-Newtonian fluid with shear-thinning properties (Carreau–Yasuda model), and viscoelastic differential fluid, the Phan– Thien/Tanner model (PTT). The post-processing are done in contour and vector form based on channel depth onto the axial flow. Considering screw moving boundary in the extruder has significant effects on pressure, stress, and velocity behaviors comparing to the obtained results from the assumption of the turning barrel boundary that currently is used to model the extrusion process. Numerical results demonstrate that the pressure and velocity profiles are opposite in the two mentioned assumptions and viscoelastic properties cause effectively to change flow behavior in the spiral direction. Furthermore, the major variables of flow are influenced by Newtonian, viscoelastic and generalized-Newtonian models in volume control output.

single screw extruder ,newtonian model,viscoelastic model,generalized newtonian model ,screw and barrel turning boundaries,rheological properties