A phase‐field based model for coupling two‐phase flow with the motion of immersed rigid bodies

The interaction of immersed rigid bodies with two-phase flow is of high interest in many applications. A model for the coupling of a Hohenberg–Halperin type model for two-phase flow and a fictitious domain method for consideration of rigid bodies is introduced leading to a full multiphase-field method to address the overall problem. A normalized phase variable is used alongside a method for application of wetting boundary conditions over a diffuse fluid-solid interface. This enables the representation of capillary effects and different wetting behavior based on Young\u27s law. A number of simulations is conducted in order to validate the model and highlight its ability to handle a variety of setups for two-phase particulate flow. This includes dynamic wetting situations, the motion of multiple particles within the two-phase flow and the interaction with arbitrarily shaped solid structures inside the domain

Modeling Anisotropic Transport in Polycrystalline Battery Materials

Hierarchical structures of many agglomerated primary crystals are often employed as cathode materials, especially for layered-oxide compounds. The anisotropic nature of these materials results in a strong correlation between particle morphology and ion transport. In this work, we present a multiphase-field framework that is able to account for strongly anisotropic diffusion in polycrystalline materials. Various secondary particle structures with random grain orientation as well as strongly textured samples are investigated. The observed ion distributions match well with the experimental observations. Furthermore, we show how these simulations can be used to mimic potentiostatic intermittent titration technique (PITT) measurements and compute effective diffusion coefficients for secondary particles. The results unravel the intrinsic relation between particle microstructure and the apparent diffusivity. Consequently, the modeling framework can be employed to guide the microstructure design of secondary battery particles. Furthermore, the phase-field method closes the gap between computation of diffusivities on the atomistic scale and the effective properties of secondary particles, which are a necessary input for Newman-type cell models

Grain-resolved kinetics and rotation during grain growth of nanocrystalline Aluminium by molecular dynamics

Grain growth in nanocrystalline Al was studied by means of molecular dynamics simulations. The novelty of this study results from the utilization of an algorithm to resolve per-grain kinetics and orientation change from molecular dynamics data sets. To this aim, a highly efficient algorithm for the identification and reconstruction of crystallites from molecular dynamics data sets of FCC materials was developed. This method is capable of calculating specific attributes of grains, namely, volume, center of mass, average orientation and orientation spread. In addition, it provides a mapping method to track grains during time-row data sets. In the present contribution, we describe and validate the algorithm, which is then used to analyze grain growth in polycrystalline Al with a weak texture. For the conditions tested, the algorithm was able to find all of the input orientations and reconstruct the grains according to their crystallographic orientation. With the help of the developed algorithms, we studied grain growth kinetics and grain rotation. The results of the simulations showed slightly slowed-down kinetics in particular in the initial stages of grain growth and marginal rotation of the grains

Modeling Anisotropic Transport in Polycrystalline Battery Materials

Hierarchical structures of many agglomerated primary crystals are often employed as cathode materials, especially for layered-oxide compounds. The anisotropic nature of these materials results in a strong correlation between particle morphology and ion transport. In this work, we present a multiphase-field framework that is able to account for strongly anisotropic diffusion in polycrystalline materials. Various secondary particle structures with random grain orientation as well as strongly textured samples are investigated. The observed ion distributions match well with the experimental observations. Furthermore, we show how these simulations can be used to mimic potentiostatic intermittent titration technique (PITT) measurements and compute effective diffusion coefficients for secondary particles. The results unravel the intrinsic relation between particle microstructure and the apparent diffusivity. Consequently, the modeling framework can be employed to guide the microstructure design of secondary battery particles. Furthermore, the phase-field method closes the gap between computation of diffusivities on the atomistic scale and the effective properties of secondary particles, which are a necessary input for Newman-type cell models