Materials such as plastics, rubber, glass, biomaterials, and food are a challenge to simulate because they exhibit viscoelastic behavior, meaning that they evolve partly as a liquid and partly as a solid. Often, these materials swell or deform considerably when they exit the die. They may also resist being stretched or blown. A wide range of constitutive equations was implemented in Fluent CFD software to capture viscoelasticity, which include differential models, such as PTT and Giesekus, and integral models, such as KBKZ. Validation studies are available to prove the accuracy and robustness of the numerical methods implemented in our software for solving viscoelastic flows.

Viscoelastic modeling of tire tread extrusion. The contours represent the velocity distribution in the die. The significant die swell is caused by viscoelastic effects.