ICAMS / Interdisciplinary Centre for Advanced Materials Simulation

Theory and Simulation of Complex Fluids

Fathollah Varnik

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). (a) Color coded shear strain within a plane passing through the center of the sample. The color scheme shows the numerical value of the strain. (b) 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.

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.

Competences

Group Members

 

Recent publications

M. R. Hassani, E. Mahmoudinezhad Zirdehi, K. Krok, P. Schall et al. Long-range strain correlations in 3D quiescent glass forming liquids Europhysics Letters, 124, 18003, (2018)

J. Kundin, R. Schiedung, H. Sohaib, I. Steinbach. Phase-field modeling of pores and precipitates in polycrystalline systems Modelling Simul. Mater. Sci. Eng., 26, 065003, (2018)

C. Schwarze, R. Darvishi Kamachali, C. Mießen, M. Tegeler et al. Computationally efficient phase-field simulation studies using RVE sampling and statistical analysis Computational Materials Science, 147, 204-216, (2018)

M. Gross, F. Varnik. Shear-density coupling for a compressible single-component yield-stress fluid Soft Matter, 14, 4577-4590, (2018)

M. R. Hassani, P. S. Engels, F. Varnik. Wall effects on spatial correlations of non-affine strain in a 3D model glass EPL Journal, 121, 18005, (2018)

Contact

apl. Prof. Dr. Fathollah Varnik
ICAMS
Ruhr-Universität Bochum
44780 Bochum
Germany

Tel: +49 234 32 29194
Fax: +49 234 32 14989

Email: fathollah.varnik@rub.de