Benjamin Bursik, SFB 1313 doctoral researcher at the Institute of Thermodynamics and Thermal Process Engineering (research project A01), will give his milestone presentation on "Modeling the Dynamics of Interfaces in Porous Media Using Hydrodynamic Density Functional Theory" on 13 January 2025.
Date: Tuesday, 13 January 2025
Time: 2 pm
Title: "Modeling the Dynamics of Interfaces in Porous Media Using Hydrodynamic Density Functional Theory"
Location: Seminar room ITT (V9.1.340), Campus Vaihingen, 70569 Stuttgart
Abstract
Predicting dynamic processes at interfaces, particularly at solid-fluid interfaces, is crucial for accurately modeling flow through porous media and requires models on both, the molecular and the macroscopic (continuum) scale. Hydrodynamic density functional theory (DFT) connects molecular modeling with macroscopic (continuum) balance equations. In this work, a framework based on hydrodynamic DFT is developed, validated and applied to the modeling of dynamic processes at interfaces on the molecular scale. The framework consists of balance equations for mass, components and momentum and includes a term from classical (equilibrium) DFT, a molecular model which allows to predict the influence of interfaces on the dynamics of the system. At the same time, the approach simplifies to the isothermal Navier-Stokes equations sufficiently far away from interfaces. The DFT term requires Helmholtz energy functionals which are based on the molecular PC-SAFT model and provide accurate predictions for interfacial properties of inhomogeneous systems in equilibrium. Constitutive equations are employed for the shear stress, by assuming a Newtonian fluid, and for molecular diffusion, which is described using the Maxwell-Stefan equations. The corresponding transport properties are determined from a generalized version of entropy scaling by extending it from homogeneous to inhomogeneous systems, specifically to solid-fluid interfaces. Three key findings are reported here: First, the underlying DFT approach accurately predicts equilibrium effects in real systems, specifically contact angles of droplets as well as solvation free energies in agreement with experimental results. Second, the entropy scaling approach remains valid for viscosities at interfaces if the effect of the solid is appropriately included in the description, providing a molecular model for local values of transport properties. Such a model goes beyond typical continuum approaches, where transport coefficients are assigned to each phase, and it was shown to be necessary for an accurate description of wetting at the microscopic scale. Third, the framework predicts wetting at the microscopic scale, including dynamic contact angles, slip at the solid-fluid interface and the rolling motion of droplets moving over a solid. These findings demonstrate that the proposed framework effectively captures the dynamics of interfaces at the microscopic scale while simultaneously advancing the development of multiscale modeling approaches.