Polymer Flow Module Updates

For users of the Polymer Flow Module, COMSOL Multiphysics® version 6.0 brings new viscoelastic and inelastic models, a Curing interface, and fluid–structure interaction for viscoelastic fluids. Learn about these and more updates below.

New Viscoelastic Model for Polymer Melts

For the Viscoelastic Flow interface, a new exponential Phan–Thien Tanner (EPTT) material model has been added. This viscoelastic model is derived from kinetic theory, which describes polymeric melts as elastic networks. The destruction of junctions between the strands in the network is assumed to be related to the average size of the network. The relaxation function is an exponential expression, which is a more accurate description of polymer melts than the linear function, LPTT. The relaxation function is used to describe the stress relaxation with time. When describing polymer melts, accurate stress relaxation and viscoelastic deformations are required and can be used in plastic extrusion and molding processes, for example.

The COMSOL Multiphysics UI showing the Model Builder with the Fluid Properties node highlighted, the corresponding Settings window, and a polymer melt model in the Graphics window.
UI settings for the EPTT model.

Sisko Model for Inelastic Flow

The Sisko inelastic model is a generalization of the power law model. It accurately describes a fluid suspension with a large volume fraction of particles, such as blood, for example. While the power law model may accurately describe the flow of these suspensions at medium shear rates, the Sisko model is also able to describe the moderate and high shear rate regimes of the flow.

The COMSOL Multiphysics UI showing the Model Builder with the Two-Phase Flow, Phase Field node highlighted, the corresponding Settings window, and a 3D model in the Graphics window.
The UI for selecting the inelastic flow models, in this case the Sisko model.

Curing Reaction Interface

The term curing refers to the crosslinking of thermosetting resins, for example an unsaturated polyester or epoxy resin. The term vulcanization is used for rubbers. A thermoset is a polymer, resin, or plastic that is irreversibly hardened by curing. For thermosets, viscosity depends both on temperature and on the degree of cure. The new Curing Reaction interface includes two predefined models for the dependence of viscosity on the degree of cure. These are the Castro–Macosko and the percolation models. The rate of the curing process can be described according to the Sestak–Berggren, Kama–Sourour, and nth-order reaction kinetics models, which are predefined in the Curing Reaction interface.

Injection molding with curing.

Fluid–Structure Interaction for Viscoelastic Fluids

The forces exerted by a viscoelastic fluid on a solid surface in a model have to be formulated specifically for each viscoelastic model. In the new version of the Polymer Flow Module, the forces from the fluid are predefined when you select the new fluid–structure interaction multiphysics couplings: Fluid-Solid Interaction, Viscoelastic Flow; Fluid-Solid Interaction, Viscoelastic Flow; and Fixed Geometry. These allow for accurate calculation of stresses and strains as well as deformation in devices used for polymer extrusion, molding, and other processes that involve viscoelastic fluids. You can view this feature in the Viscoelastic Flow Through a Channel with a Flexible Wall tutorial model. Note that the Fluid-Solid Interaction, Viscoelastic Flow interface also requires a license for either the Structural Mechanics Module, MEMS Module, or Multibody Dynamics Module.

A wall model showing the velocity magnitude in the Prism color table and the load represented by white arrows.
Fluid–structure interaction used to model flow in an elastic channel.

Flow in Porous Media

The Brinkman Equations interface is now available with the Polymer Flow module. It is also possible to use predefined formulations for models with free and porous media flows. The functionality may be used to describe the flow of fluids across filters, sieves, and other devices that contain components made of porous materials.

Two-Phase Flow in Porous Media

A new multiphysics interface combines the Brinkman Equations and Level Set interfaces, and automatically adds a Two-Phase Flow, Level Set coupling node. It solves for conservation of mass and momentum with the Brinkman equations. The interface between two immiscible fluids in porous media is tracked with the level-set function.

Resin showed in the Aurora Australis color table, injecting into an empty mold model.
Resin injection into an empty mold. The new interface is used to track the injection front. The mold contains one inlet and three outlets, and a porous block in the center, and it is initially filled with air.

Porous Slip for the Brinkman Equations Interface

The boundary layer in flow in porous media may be very thin and impractical to resolve in a Brinkman equations model. The new Porous slip wall treatment feature allows you to account for walls without resolving the full flow profile in the boundary layer. Instead, a stress condition is applied at the surfaces, yielding decent accuracy in bulk flow by utilizing an asymptotic solution of the boundary layer velocity profile. The functionality is activated in the Brinkman Equations interface Settings window and is then used for the default wall condition. You can use this new feature in most problems involving subsurface flow described by the Brinkman equations and where the model domain is large.

A porous reactor model showing the flow and concentration in the Rainbow color table.
The flow and concentration field of a porous reactor model.

Greatly Improved Handling of Porous Materials

Porous materials are now defined in the Phase-Specific Properties table in the Porous Material node. In addition, subnodes may be added for the solid and fluid features where several subnodes may be defined for each phase. This allows for the use of one and the same porous material for fluid flow, chemical species transport, and heat transfer without having to duplicate material properties and settings.

A closeup view of the Model Builder with the Porous Material node highlighted, the corresponding Settings window, and a packed-bed reactor model in the Graphics window.
The new Materials node for Porous Material exemplified on a multiscale model of a packed bed.

New Tutorial Models

COMSOL Multiphysics® version 6.0 brings two new tutorial models to the Polymer Flow Module.