Coalescence dynamics of viscous conical drops

Area of Science:

• Fluid dynamics
• Interfacial phenomena
• Colloid science

Background:

• Oppositely charged liquid drops form a meniscus bridge upon contact.
• A critical cone angle exists, above which drop coalescence is inhibited.
• Previous studies focused on inertial drops, with limited understanding of viscosity's role.

Purpose of the Study:

• To investigate the influence of liquid viscosity on the critical cone angle for drop coalescence.
• To explore the dynamics of conical drop coalescence at intermediate Reynolds numbers.
• To provide insights into the interplay of viscous, inertial, and surface tension effects.

Main Methods:

• High-fidelity numerical simulations were employed.
• Simulations accounted for viscous, inertial, and surface tension forces.
• The study focused on the coalescence dynamics of double-cone geometry liquid bridges.

Main Results:

• The critical cone angle for drop coalescence increases with decreasing liquid viscosity.
• At low viscosities, approaching the inertial regime, the critical angle stabilizes near 27°.
• Simulation results align with experimental observations in the inertial limit.

Conclusions:

• Liquid viscosity significantly influences the critical cone angle, affecting drop coalescence.
• The findings have implications for controlling coalescence in emulsions and electrospray ionization.
• Numerical simulations provide a valuable tool for understanding complex interfacial fluid dynamics.