Flowing matter in porous media
Location: Zuse Institute Berlin, Germany
Organisers
Fluid transport in porous media is a research topic which has found wide use and was pushed further in diverse fields: With origins in the industrial recovery of petroleum oil, modern applications include geological CO2 storage, sustainable construction materials, or drug release from hydrogels [1, 2]. From geophysical scales down to the (sub-)micrometre scale of single pores, fluid mechanical models with effective material parameters are prevalently employed to predict flows and transport. However, realistic pore models (e.g., boundary conditions) and up-scaling approaches need information about the molecular behaviour at the nanoscale [2], where hydrodynamic permeability models are prone to break down [3].
On the molecular scale, there is also a genuine and sustained interest in the design of tailored nanoporous materials with controlled structure–function relationships, promising material classes for applications such as gas capture and species separation are metal-organic frameworks (MOFs) [4, 5], thermally rearranged (TR) polymer membranes, and amorphous carbon molecular sieves (CMSs) [6, 7]. Alkali diffusion in silicate gels is relevant for low-carbon cements [8], and the conduction of lithium ions in amorphous silicon is a key mechanism in high-performance batteries [9]. Going beyond the classical questions, there is recent interest in self-generated flows in the context of confined active matter [10–12] and due to chemically active surfaces [13].
Fluid flow through nanoporous media using non-equilibrium molecular dynamics (NEMD) simulations has been investigated with low intensity since the 1990’s [14] but has only recently seen a surge in research activity. The focus is typically on the permeability of ordered porous media such as MOFs [15, 16] and linear or slit-shaped pores [17, 18], but also through disordered organic materials [3, 19, 20]. The majority of these studies addresses the transport of molecules in the gas phase or of low-density fluids, while NEMD simulations for dense liquids face particular technical challenges. One approach to stationary fluid flow is to prescribe the chemical potential of the inlet and outlet by means of grand-canonical (GC) reservoirs (dual control volume set-up) [19–21]. However, the Monte Carlo insertion of particles would become inefficient for dense liquids; here spatially adaptive resolution simulations (AdResS) offer a novel alternative to GC-NEMD simulations [22, 23]. Another line of approach to stationary flow is driving the liquid in a boundary region of a periodic set-up by applying an external force to maintain a pressure difference [17, 18], a concentration gradient [16], or a custom flow profile [24].
Last, but not least, there have been advances in the microscopic theory of confined or (randomly) pinned liquids in equilibrium [25, 26] and for bulk liquids under flow [27, 28]. Extending these theories to flowing states under confinement appears highly welcome for the interpretation of simulation data and related experiments, thus paving the way for quantitative predictions for the corresponding applications.
References
Juergen Horbach (Heinrich Heine University Duesseldorf) - Organiser
Felix Höfling (Freie Universität Berlin) - Organiser
Netherlands
Liesbeth Janssen (Eindhoven University of Technology) - Organiser
Poland
Anna Maciolek (Institute of Physical Chemistry Polish Academy of Sciences) - Organiser