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Particle surface roughness plays a pivotal role in dictating the rheological behavior of dense suspensions of rigid particles as it promotes interparticle contacts, leading to friction and contact stresses. This suggests that roughness must have a significant impact on the shear thickening behavior of suspensions, as friction is considered to be the underlying mechanism for shear thickening in dense suspensions. To this end, we numerically investigate the effects of systematically increasing the particle surface roughness on shear thickening suspensions. We show that increasing roughness leads to early onset of shear thickening, especially discontinuous shear thickening, in terms of both the critical shear rate and the critical volume fraction. In addition, roughness enhances the strength of the shear thickening effect as it leads to increase in the viscosity of dense suspensions. We explain these results by investigating the role of roughness in the evolution of contact networks and the jamming fraction. Increasing roughness leads to denser contact networks with high contact stresses and reduction in the jamming fraction. Finally, we visualize the effect of roughness on the phase diagram for viscosity in the shear rate–volume fraction plane. The results presented in the paper are consistent with recent experimental studies, which indicates that the computational framework developed can be utilized to predict and tune suspension behavior for specific applications.
More et al. (Sun,) studied this question.