Coarse Grained Modeling of Multiphase Flows with Surfactants.

Thao X D Nguyen,Tuan V Vu,Dimitrios V Papavassiliou,Sepideh Razavi

doi:10.3390/polym14030543

Thao X D Nguyen, Tuan V Vu + Show 2 more

Open Access

https://doi.org/10.3390/polym14030543

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Journal: Polymers	Publication Date: Jan 28, 2022
Citations: 6	License type: CC BY 4.0

Affiliation: University of Oklahoma

Abstract

Coarse-grained modeling methods allow simulations at larger scales than molecular dynamics, making it feasible to simulate multifluid systems. It is, however, critical to use model parameters that represent the fluid properties with fidelity under both equilibrium and dynamic conditions. In this work, dissipative particle dynamics (DPD) methods were used to simulate the flow of oil and water in a narrow slit under Poiseuille and Couette flow conditions. Large surfactant molecules were also included in the computations. A systematic methodology is presented to determine the DPD parameters necessary for ensuring that the boundary conditions were obeyed, that the oil and water viscosities were represented correctly, and that the velocity profile for the multifluid system agreed with the theoretical expectations. Surfactant molecules were introduced at the oil–water interface (sodium dodecylsulfate and octaethylene glycol monododecyl ether) to determine the effects of surface-active molecules on the two-phase flow. A critical shear rate was found for Poiseuille flow, beyond which the surfactants desorbed to form the interface forming micelles and destabilize the interface, and the surfactant-covered interface remained stable under Couette flow even at high shear rates.

Highlights

Computations that are focused on the molecular scale such as molecular dynamics (MD) simulations can be used as tools to probe multifluid flows, flows with large molecules, particulate flows, and interfacial phenomena [5,6,7,8]
We focused on the velocity distribution of two immiscible fluids in the presence of surface-active molecules
We found that macroscopically observed hydrodynamic behavior agreed with findings from the molecular dynamics when the interaction parameters appearing in the conservative force (see Equation (1) were modified

Summary

Introduction

The interfacial behavior of immiscible fluids is important for understanding, predicting, and controlling systems that involve oil–water or oil–gas flows. Multilayer coating applications, separation applications, environmental remediation of contaminated regions in the subsurface, and petroleum engineering applications for oil mobilization are examples where such flow systems are important [1,2,3,4]. MD techniques are computationally expensive and even unfeasible when investigating large scale systems or systems with very large molecules, because of the very small length and time scales employed (on the order of Angstroms and femtoseconds, respectively). In contrast to MD, coarse-grained modeling techniques such as dissipative particle dynamics (DPD) can meet the need for larger particle sizes and longer time steps [9]

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