Theory and Simulation of Complex Fluids
The main research activity of the complex fluids group focusses on transport phenomena and phase transformations in fluidic media.
Problems addressed by the group include a variety of physical phenomena such as wetting and capillarity, rheology and shear-induced diffusion in dense suspensions of deformable particles (such as red blood cells and vesicles), deformation and response in highly viscous amorphous materials and chemo-mechanical coupling in shape memory polymers.
On the methodological side, the group uses molecular dynamics (MD) simulations, the lattice Boltzmann method (LBM) as well as hybrid approaches combining the LBM for fluid flow either with MD for particle dynamics in the flow or with finite element method (FEM) to study suspension rheology of deformable closed membranes as a model for red blood cells and vesicles.
Molecular dynamics simulation results on shear band formation in a model metallic glass (a binary Lennard-Jones alloy). (left) Color coded shear strain within a plane passing through the center of the sample. The color scheme shows the numerical value of the strain. (right) The distribution of a non-local measure of the excess volume obtained from Voronoi-tessellation. Here, each data point gives the correlation between the excess volume of a particle and its nearest neighbours. Simulations performed by Muhammad R. Hassani using LAMMPS.
Recently, the complex fluids group commenced to combine the phase field (PF) method for phase transformation kinetics and microstructure evolution with the lattice Boltzmann method in order to account for the effect of transport by the flow on the interface dynamics during solidification. This approach has been further extended by introducing wetting and capillarity into the coupled PF-LBM scheme and is used to investigate effects of capillarity-induced grain rearrangements on the microstructure in liquid phase sintering.
During the past five years, the group has also made major contributions to the methodological development within the lattice Boltzmann framework. By introducing thermal fluctuations within the so-called non-ideal fluid lattice Boltzmann methods, the LBM has been advanced to the stage of addressing wetting phenomena on the nano-scale.
Animation of the microstructure evolution in a metallic foam using a multi-phase-field/CFD approach. Click on image to start movie.
Competences
- Lattice Boltzmann modelling
- Supercooled liquids and glasses
- Suspension rheology
- Molecular dynamics of polymers
- Phase field-Lattice Boltzmann coupling
Group Members
Recent publications
A. Lagogianni, F. Varnik. Temperature rise inside shear bands in a simple model glass International Journal of Molecular Sciences, MDPI AG,, 23, 12159, (2022)
M. M. Bruns, F. Varnik. Enhanced dynamics in deep thermal cycling of a model glass The Journal of Chemical Physics, AIP Publishing,, 156, 234501, (2022)
H. Wang, K. Uhlmann, V. Vedula, D. Balzani et al. Fluid-structure interaction simulation of tissue degradation and its effects on intra-aneurysm hemodynamics Biomechanics and Modeling in Mechanobiology, Springer Science and Business Media LLC,, 21, 671–683, (2022)
H. Wang. Computational study of hemodynamic changes associated with morphology, deformability and degradation of blood vessels PhD Thesis, Ruhr-Universität Bochum, Max-Planck-Institut für Eisenforschung (2022)
M. M. Bruns, F. Varnik. Rejuvenation in deep thermal cycling of a generic model glass: a study of per-particle energy distribution Materials, MDPI AG,, 15, 829, (2022)
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Contact |
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Prof. Dr. Fathollah Varnik ICAMS Ruhr-Universität Bochum 44780 Bochum Germany Tel: +49 234 32 29194 Email: fathollah.varnik@rub.de |
