POLYFLOW

Fig. 37. Strain rate distribution along the centerline in a 2-dimensional hyperbolic flow (the flow geometry is shown as an insert). The solid curve, redrawn according to ref. 131, corresponds to a viscoelastic fluid (the spike at x = 2 is a calculation artefact) the dotted curve is calculated with POLYFLOW for a Newtonian liquid...

Polyflow, a finite element program for calculating viscous and viscoelastic flows, Polyflow SA, Place de l Universite 16, B-1348 Louvain-la-Neuve, Belgium (1988)... 

Computer aided design (CAD)/computer-aided manufacture (CAM) programs have been developed to carry out the necessary calculations. One current system known as Polyflow is offered by a Belgian organisation (Polyflow SA). Polyflow can be used to calculate three-dimensional flow and die swell, using finite element analysis. Other systems are available. 

Fig. 13.34 Velocity vectors from PTV experiments with the Newtonian PB H-100. (a) Ca = 2.0 (h) Ca — 0.1 FEM POLYFLOW streamlines for the same fluid (c) Ca = 2.0 (d) Ca = 0.1. [Reprinted hy permission from V. Gauri and K. W. Koelling, Gas-assisted Displacement of Viscoelastic Fluids Flow Dynamics at the Bubble Front, J. Non-Newt. Fluid Meek, 83, 183-203 (1999).]...

Several commercially available programs from different manufacturers are suitable in principle for the calculation of flows in twin screw extruders they include but are not limited to Cfx, Fluent, Polyflow (respectively Ansys) and Star-CD (CD-adapco). This list includes the programs tested and used by the author. The program manufacturers offer a number of introductory courses to instruct users in the effective use of the solver and postprocessing. These are recommended for all CFD newcomers. 

The simulation of non-Newtonian fluid flow is significantly more complex in comparison with the simulation of Newtonian fluid flow due to the possible occurrence of sharp stress gradients which necessitates the use of (local) mesh refinement techniques. Also the coupling between momentum and constitutive equations makes the problem extremely stiff and often time-dependent calculations have to be performed due to memory effects and also due to the possible occurrence of bifurcations. These requirements explain the existence of specialized (often FEM-based) CFD packages for non-Newtonian flow such as POLYFLOW. 

POLYFLOW is a commercial fluid-flow simulation program from Unite de Mecanique Appli-quee, Universite Catholique De Louvain, Batiment Stevin 2, Place Du Levant, B-1348 Louvain-La-Neuve, Belgium. 

Polyflow (application software) Fluent Inc. Lebanon, NH http //www.fluent.com/software/ polyflow (accessed Mar 2005). 

Mesh superimposition. This technique used in commercial finite element CFD software, like FIDAP and PolyFlow , consists of generating a volume mesh without the moving impellers... 

To reduce this effort, the software Polyflow (Fluent, Lebanon, USA) contains a special module to avoid the remeshing of the flow channel for every single timestep. This is called the Mesh Superposition Technique , where the inner barrel and the screw are meshed separatly. The discrete meshes are overlayed to create one system where the surfaces of the screw define the channel boundary. A major issue with this method is that the flow channel volume varies as the intersection of the surface elements leads to unequal sums over all elements. This is compensated by a compression factor on which the simulation results react very sensitively. 

POlyflow. [Morton IntT.] Flow additive to pigment printing. 

In the first approach, a numerical model was developed by utilizing the ANSYS POLYFLOW solver in conjtmction with both tire Mesh Superposition Technique and tire Lagrangian adaptive remediing technique to model plunger motion and gob formation... 

The commercial software ANSYS POLYFLOW is most widely used witiiin all three of the major glass industries (container, flat, and fiber). Early simulation works on glass container forming process with POLYFLOW have been done by Hyre, et al. ". They developed comprehensive simulations of the overall container forming process (forehearlh, feedH gob... 

For ANSYS POLYFLOW model, the moving parts, such as the plunger, were taken into account utilizing a Mesh Superposition Technique (MST). The geometries and meshes of the... 

For the hybrid model (ANSYS FLUENT POLYFLOW), the moving parts were taken into consideration using a sliding and dynamic mesh model in FLUENT. As shown in Fig. 4, smoothing and dynamic layering methods were adopted to adjust the mesh of a zone with moving and/or deforming boundaries. The total cell count for the hybrid model is 126,000. 

ANSYS POLYFLOW incorporates a method known as Mesh Siqierposition Technique (MST) to simulate transient flows with internal moving parts. In this study, vidien the plunger me is imposed over the glass mesh as shown in Fig. 3, the conservation of mass, momentum and energy equations (1), (2) and (S) must be modified. 

Lagrangian me updated and TGrid adqitive remeshing method in ANSYS POLYFLOW... 

A fiiee surface boundary condition was imposed on the glass gob sur ce in POLYFLOW. Since the fiiee surface boundary position is not known in advance, the fiee-sur ce problems have additional degrees of freedom and additional equations to solve as coitqrared widi fixedboundary flow problems. For a transient flow problem, the position of moving boundaries is determined by solving a kinematic equation ... 

For both approaches/models, the total physical time for numerical simulation is 0.3 s. We assume that the glass gob will be sheared off after 0.3 s. Since ANSYS POLYFLOW is not capable of modeling the shearing process, the simulation ends before the glass gob was sheared. 

In this study, the time step used in transient calculation is 0.001 s for both ANSYS POLYFLOW model and hybrid model (FLUENT/POLYFLOW). Numerical computations were run with 8 cores on a workstation with Intel Xeon CPUs ES-2640 2.5GHz. 

Figure 7 Velocity distribution for steady state isothermal POLYFLOW model...

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