BOUNDARY-ELEMENT ANALYSIS OF 3-DIMENSIONAL MIXING FLOW OF NEWTONIAN AND VISCOELASTIC FLUIDS

The boundary element method (BEM) is implemented for the simulation of three-dimensional transient flows of typical relevance to mixing. Cre eping Newtonian and viscoelastic fluids of the Maxwell type are examin ed. A boundary-only formulation in the time domain is proposed for lin ear viscoelastic flows. Special emphasis is placed on cavity flows inv olving simple- and multiple-connected moving domains. The BEM becomes particularly suited in multiple-connected flows, where part of the bou ndary (stirrer or rotor) is moving, and the remaining outer part (cavi ty or barrel) is at rest. In this case, conventional methods, such as the finite element method (FEM), generally require remeshing or mesh r efinement of the three-dimensional fluid volume as the flow evolves an d the domain of computation changes with time. The BEM is shown to be much easier to implement since the kinematics of the elements bounding the fluid is known (imposed). It is found that, for simple cavity flo w induced by a rotating vane at constant angular velocity, the tractio ns at the vane tip and cavity face exhibit non-linear periodic dynamic al behavior with time for fluids obeying linear constitutive equations . (C) 1998 John Wiley & Sons, Ltd.