Non-colloidal suspension Taylor-Couette flows: flow instabilities and hysteresis*

We employed suspension balance model (SBM) and rheological constitutive laws to numerically examine the Taylor-Couette flow of concentrated, neutrally buoyant, and non-colloidal suspensions when the inner cylinder is rotating and the outer one is stationary. The bulk particle volume fraction was varied ϕ_b = 0.1 ~ 0.3, while the radius ratio of cylinders η and the particle size ratio ϵ (= d/a) were fixed at 0.877 and 60, respectively; d is the gap width of cylinders and a is the radius of particles. By varying the suspensions Reynolds number based on the rotating angular velocity and the effective viscosity of suspensions, we also analyzed the imapct of suspended particles on flow transition. Although in the model the inertial migration of particles is neglected, similar to the recent reported experiments, we observed the circular Couette flow (CCF) transitions via ribbons (RIB), spiral vortex flow (SVF), and wavy spiral vortex flow (WSVF) to wavy vortex flow (WVF). We also found a hysteresis during the transitions where the transitons to higher modes occur early for more dense suspensions. Friction and torque coefficients of the suspension flow are also computed and compared.