Electrohydrodynamic Interactions of Droplets and Bubbles in Quiescent and Dynamic Non-Newtonian Media

Extensive research has been conducted on the electrohydrodynamics (EHD) of droplets and bubbles in Newtonian fluids. Studies have explored deformation, migration, and coalescence of droplets under DC and AC electric fields, focusing on parameters such as conductivity, permittivity, and surface tension.

The interplay between the electrical and surface tension force (electric capillary number) , have profound implications for diverse applications such as emulsion stability, biomedical devices, inkjet printing, and electrostatic precipitation. These insights have led to significant advancements in manipulating Newtonian systems. However, in quiescent and dynamic non-Newtonian Media, the complexities increase due to the interplay of shear-dependent viscosity, and electrical forces. While some studies have investigated the deformation of a single droplet in a simple;quiescent media, they often neglect the coupling effects of rheological properties with electric field-induced stresses of moving fluid in between droplets or bubbles.

Furthermore, experimental studies often face challenges in isolating specific size and shape of droplet/bubble, while computational models for non-Newtonian EHD systems are still in their infancy. These gaps hinder a comprehensive understanding of EHD phenomena in non-Newtonian;systems and limit the development of robust predictive models. Existing computational models often fail to capture the intricate coupling of nonNewtonian fluid mechanics with EHD forces, especially in multiphase systems.

The methodology of the proposed study may be tentatively described in the following manner:

• Conduct experiments on controlled non-Newtonian systems using high-speed imaging and electrical diagnostics to capture droplet and bubble behaviour under electric fields.

• Computational Modelling: Develop numerical simulations based on the Volume of Fluid (VOF) method (may be explore Level-Set method to simulate the EHD interactions in non-Newtonian media). Incorporate rheological models to account for shear-thinning or viscoelastic effects.

• Parametric Study: Perform a systematic investigation of key parameters, including electric field strength, droplet size, fluid rheology, and interfacial tension, to identify trends and governing mechanisms.

This project seeks to advance the field of EHD by addressing the complex interactions of droplets and bubbles in non-Newtonian media. By integrating experimental observations with computational modelling, the research aims to provide a foundational understanding that can drive innovation in various applications involving non-Newtonian fluids.