ENTRANCE LENGTH AND PULSATILE FLOWS OF A MODEL CONCENTRATED SUSPENSION

The flow behaviour of Phillips et at's suspension model [Phys. Fluids A 4, 30 (1991)] in channel and pulsatile flows is investigated by a co mbination of analytical and numerical methods (using an unstructured f inite volume method). In the channel flow, we found that the kinematic s develop faster I than the concentration, with an entrance length of 0.2H(3)/a(2), where H is the channel half width, and a is the particle s' radius. The corresponding entrance length for the concentration is 0.5H(3)/a(2). In time-periodic flows, the steady-state kinematics and the stresses are periodic in time, and yet the steady-state concentrat ion (and thus the viscosity) is time-independent. This feature is perh aps a critical test of the model, and indeed of any model in which the flux is quasi-linear in the generalized strain rate. (C) 1996 Society of Rheology.