Ansys Polyflow solves a broad range of applications where the fluid exhibits complex deformation properties. Various differential and integral models are presented in Viscoelastic Flows, with a detailed description of problem setups.
For the models presented in Viscoelastic Flows, and the generalized Newtonian models introduced in Generalized Newtonian Flow, we assume that the morphology of the fluid remains unchanged. In some circumstances and for some fluids such as Nylon, the fluid undergoes some structural changes, because of the flow induced crystallization (FIC) mechanism.
A model has been recently proposed for describing the FIC [12]. It involves a combined description of both amorphous and semicrystalline phases. It is based on a tensorial description of the configuration for the amorphous phase and of the macro-molecular orientation for the semicrystalline phase.
An understanding of the following features of the model may help a few to obtain the best possible results from this model, without unrealistic expectations.
This model ([12]) is new, and may be improved in the future.
Some alterations have been made to the model for a convenient software implementation and for controlling the solution under no flow (rest state). Hence, there will be slight deviations when you compare the original paper to this chapter.
The model is based on a tensorial description with appropriate transport equations for crystallization. The strongly coupled, highly nonlinear resulting system can affect the calculation time and the convergence of the solver. Hence it requires a careful problem setup with appropriate evolution schemes.
The paper (see [12]) proposes numerical values for all model parameters required for simulating FIC occurring in Nylon. An experimental protocol does not exist for the determination of numerical parameters. Hence, a possible user’s database is the best source of information.