Journal of Non-Newtonian Fluid Mechanics, Vol.124, No.1-3, 77-91, 2004
Simulation and analysis of oscillatory squeeze flow
Basic viscoelastic 'lubrication' theory of dynamic squeeze-flow rheometry by Phan-Thien [J. Aust. Math. Soc. 22 (1980) 22] has recently been extended by Bell et al. [A comprehensive theory for the compressional rheometer, in: Proceedings of the Joint Meeting of British, Italian, Portuguese and Spanish Rheologists, Torremolinos, April 24-26, 2002, unpublished]. It yields relationships between linear oscillatory properties, experimental conditions, and the force required to maintain small plate displacement under no-slip conditions. Dynamic rotary shear measurements of G' and G' provide a relaxation spectrum which has been used to determine the parameters of a multi-mode Giesekus constitutive model. This rheological model is next employed to predict the periodic force in an oscillatory squeeze flow; the calculation is performed with the finite element software POLYFLOW. In particular, we focus on identification of the strain limit at varied plate gap and frequency for linear viscoelastic behaviour. The calculated force for deformation has then been used in the basic theory to give predicted G' and G". For A1 fluid, it is found that inertia correction becomes significant by 10 Hz and is dominant by 100 Hz. The predicted values compare well with results previously found by dynamic shear rheometry; and comparison with dynamic squeeze-flow results is in progress using prototype equipment provided by TA Instruments Ltd. Some numerical predictions have also been obtained for the force needed with full-slip at the plates. (C) 2004 Elsevier B.V. All rights reserved.