LBM-DEM coupled simulations to explore the diverging viscosity scaling of granular suspensions

What is it about?

We perform constant-volume shearing simulations of non-Brownian granular suspensions using the discrete element method coupled with the lattice Boltzmann method. We choose a wide range of solid fractions, shear rates, fluid viscosities, particle sizes, particle stiffness, and inter-particle frictional coefficients to obtain a scaling solution for the viscous behavior of suspensions in both semi-dilute and dense regimes. This result demonstrates that, with the semi-dilute-dense transitional solid fraction, there exists a strong correlation between the inverse relative viscosity and the shear stress. The transitional behavior of suspensions closely corresponds to the microstructure development, especially the largest particle cluster. This work incorporates both the solid fraction dependence and the shear rate dependence of suspension viscosity in a universal framework, which provides a scaling solution for granular suspensions across semi-dilute and dense regimes and sheds light on the jamming transition mechanisms.

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Why is it important?

This work reports an interesting phenomenon, which is not limited within numerical studies with LBM-DEM coupled simulations. Similar results can be found in others' experimental works. In our work, we tried to explain this phenomenon based on the particle-scale analyses, such as fluid-solid interactions, cluster sizes, correlation length, and so on. In the end, it brings some insights in understanding the underlying mechanisms of this viscosity scaling related to granular suspensions.