Double emulsion generation in shear-thinning fluids under electric field effects

• Published in: International journal of mechanical sciences 2024-11, Vol.281, p.109556, Article 109556
• Main Authors: Khoshnevis, Arman, Ahmadpour, Ali, Amani, Ehsan
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics (CFD); Double emulsion generation; Dual Co-flowing; Electric field effects; Microfluidics; Non-Newtonian fluids
• ISSN: 0020-7403
• DOI: 10.1016/j.ijmecsci.2024.109556

•Non-Newtonian double emulsion generation manipulated by electric forces is investigated for the first time.•In-house UDF codes are developed to accompany the VOF-CSF method.•A new physical insight is provided into the combined effect of the outer phase viscosity variation and electric forces.•The dual effect of electric forces on the non-Newtonian double emulsion generation process is unveiled.•Various pertinent measures are introduced to quantify the problem. Double emulsions are encapsulated microstructures with medical, food, and cosmetics applications. Precise control over their parameters, such as volume, thickness, and size distribution, is crucial. This study numerically investigates, for the first time, the generation of double emulsions in a shear-thinning outer fluid under the influence of an external DC electric field. A dual co-flowing microfluidic device is chosen as the flow domain, and the shear-thinning behavior of the outer fluid is approximated by the Carreau–Yasuda rheological model. The governing equations are discretized on structured numerical grids using the VOF-CSF model and the finite volume method. The combined effects of the shear-thinning behavior and electric forces on compound droplet formation parameters, including volume, eccentricity, maximum thickness, and jet length, are studied carefully. Results show that for highly shear-thinning fluids, the application of electric forces can ensure the generation of desired compound droplets, which is not feasible without electric field effects. However, excessive electric forces can disrupt the droplet generation process, especially for moderate to low shear-thinning fluids. These findings provide new insights into the role of external electric fields in double emulsion generation and highlight their potential to optimize the production process. [Display omitted]