(142bx) Development of a Viscoelastic Two-Phase CFD Model in Openfoam
When polymers with different rheologies are blended together, there is often a need to break up large polymer droplets into smaller droplets. It is desirable to be able to explore the effects of the polymer rheology, equipment design, and operating conditions on droplet break-up efficiency using computational fluid dynamics (CFD). Previous CFD studies looked at polymer droplets flowing past a series of wires using shear thinning viscosity models and two-phase volume-of-fluid (VOF) methodology. The droplet break-up predictions were in qualitative agreement with experimental results. However, it was felt that the predictions would be improved if viscoelastic effects were also included. Since there are presently no commercial CFD codes that can perform this type of simulation a project was initiated to develop a new solver which handles viscoelastic two-phase flows. The first generation of this solver combined the VOF method and the recently added viscoelastic capabilities in OpenFOAMR to simulate free-surface flows of viscoelastic materials using various constitutive equations, including Oldroyd-B, FENE-CR, Phan-Thien-Tanner, and Giesekus models. The numerical algorithm is validated using two well-known viscoelastic free-surface effects, namely the Die Swell effect and the Weissenberg (Rod Climbing) effect, as wells as transient and steady-state deformation of single drops subject to shear and planar elongational flows. Application of this model to polymer droplet break-up is also explored.