Taylor-Couette flows of semi-dilute and concentrated non-colloidal suspensions*

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. We varied the bulk particle volume fraction ϕ_b = 0.1 ~ 0.3, while the radius ratio of cylinders is η = 0.877 and the particle size ratio is ϵ (= d/a) = 60, d is the gap width of cylinders and a is the radius of particles. By varying the Reynolds number of suspensions 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 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 at more dense suspensions. Moreover, friction and torque coefficients of the suspension flow are computed and compared.