Numerical simulation on the effects of the viscosity contrast of a soft particle at the transition between tank-treading and tumbling motions

There are mainly two types of motion for a soft particle moving in a fluid: tank-treading and tumbling motions. This transition from one mode to the other is very important for the rheological characteristics of the suspension, due to the significant changes in its macroscopic viscosity. In this study, we focused on the critical internal and external viscosity contrast, which is one of the parameters that determine the motion of a soft particle. The critical internal and external viscosity contrast was defined at the transition point between the motion modes. Consequently, the effects of capillary number and reduced area on the critical internal and external viscosity contrast were investigated. Our results confirmed that the effect of capillary number was minor, while the effect of the reduced area was significant.