Numerical investigation of non-Newtonian droplet collisions: Comparison of volume of fluid and the local front reconstruction method with experimental data

• Published in: Chemical engineering science 2024-11, Vol.299, p.120428, Article 120428
• Main Authors: Huijgen, A.H., García Llamas, C., Durubal, P.M., Buist, K.A., Kuipers, J.A.M., Baltussen, M.W.
• Format: Article
• Language: English
• Subjects: Direct numerical simulations; Droplet collisions; Local front reconstruction method; Non-Newtonian fluids; Volume of fluid
• ISSN: 0009-2509
• DOI: 10.1016/j.ces.2024.120428

Droplet-droplet collisions of non-Newtonian fluids are often encountered in industrial applications such as spray drying, fluid catalytic cracking, coating and granulation. However, there has been limited focus on a comprehensive analysis of the dynamics of these non-Newtonian binary droplet collisions. In this work, the non-Newtonian binary droplet collisions of 500 ppm xanthan gum solutions are simulated using the Volume of Fluid method and the Local Front Reconstruction Method to determine the applicability of these methods for the simulations of binary non-Newtonian droplet collisions. After verification, the simulations are compared to experimental data from literature. The outcomes for off-center collisions in the simulations resemble the experimental observations, including the oscillation of the ligament. For head-on collisions, the initial interactions and collision dynamics can be predicted with both methods at low Weber numbers, while LFRM shows improved performance at higher Weber numbers. Further, the use of an effective viscosity for the simplified representation of the droplet collision has been proven unsuccessful due to the absence of a universal effective viscosity for all situations. •Simulation of binary droplet collisions of xanthan gum using the Volume of Fluid method (VOF) and the Local Front Reconstruction Method (LFRM).•The non-Newtonian rheology of xanthan gum is modeled using the Carreau-Yasuda model, which is verified with analytical solutions.•The capabilities of VOF and LFRM are evaluated by comparing the droplet deformations with experimental results from the literature.•Both VOF and LFRM can capture the initial deformations observed experimentally, where LFRM outperforms VOF at higher impact velocities.•Using an effective viscosity to mimic the non-Newtonian behavior is a valid assumption for the effect of a non-Newtonian rheology.