Coarse Grained Modeling of Multiphase Flows with Surfactants

Area of Science:

• Computational physics
• Fluid dynamics
• Materials science

Background:

• Coarse-grained modeling enables large-scale simulations beyond molecular dynamics.
• Accurate model parameters are crucial for simulating multifluid systems under equilibrium and dynamic conditions.

Purpose of the Study:

• To simulate oil-water flow in a narrow slit using dissipative particle dynamics (DPD).
• To investigate the effects of surfactant molecules on two-phase flow dynamics.
• To develop a methodology for accurate DPD parameter determination.

Main Methods:

• Utilized dissipative particle dynamics (DPD) for multifluid simulations.
• Simulated Poiseuille and Couette flow conditions for oil and water.
• Incorporated large surfactant molecules (sodium dodecylsulfate, octaethylene glycol monododecyl ether) at the oil-water interface.

Main Results:

• Developed a systematic method to determine DPD parameters for accurate boundary conditions, fluid viscosities, and velocity profiles.
• Identified a critical shear rate in Poiseuille flow where surfactants desorb, forming micelles and destabilizing the interface.
• Observed stable surfactant-covered interfaces under Couette flow, even at high shear rates.

Conclusions:

• DPD is effective for simulating complex multifluid systems with surfactants.
• Surfactant behavior and interface stability are highly dependent on flow conditions (Poiseuille vs. Couette) and shear rate.
• Findings provide insights into controlling interfacial phenomena in microfluidic applications.