Viscoelastic Low-Reynolds-Number Flows in Mixing-Separating Cells
Proceedings of the Sixth International Conference on Engineering Computational Technology
In this work we investigate the flow of Newtonian and viscoelastic fluids in a mixing-separating geometry consisting of two opposed channel flows interacting through a gap in the common separating wall. This type of flow was experimentally investigated by Cochrane et al.  using Newtonian and viscoelastic fluids at low Reynolds number flows (Re < 40). In the present numerical study we assess the effects of Deborah and Reynolds numbers and gap size on the two-dimensional flow dynamics. The
... w dynamics. The normalized gap size was varied between 0 and 5, Re varied between 0 and 50 and De varied between 0 and the maximum attainable value. For Newtonian fluids the creeping flow is anti-symmetric, due to the anti-symmetry of the fully-developed inlet conditions and the symmetry of the flow geometry. Increasing the gap size increased the reversed flow rate ratio (R r ), here defined as the ratio between the reversed and total flow rates. In this investigation we also investigate in detail the creeping flow of viscoelastic fluids obeying the upper-convected Maxwell model for which two distinct flow patterns are found. For normalized gap sizes below a critical value the reversed flow is slightly enhanced by viscoelasticity, followed by a decrease in R r towards zero as De further increases. For a supercritical gap size viscoelasticity is responsible for a continuous increase in R r . This flow type transition can be exploited to promote mixing, and this application will also be addressed in this work.