Extensional flow of polymeric dispersions

A general-purpose extensional flow mixer, EFM, was recently introduced. To improve the understanding of its performance and potentials, several fundam ental studies were initiated. These can be divided into two groups: (i) stu dies of the model drop deformation and breakup, and (ii) studies of the flo w through EFM. Experimental, theoretical, and numerical methods (finite or boundary element methods, FEM or BEM, respectively) have been employed. The paper summarizes these efforts. The experimental study of flow of Newtonia n and viscoelastic drops through a slit showed a difference in deformabilit y. Initially, the former are reluctant to deform, but then deformation is r apid, whereas the viscoelastic drops initially deform readily, but then the deformation slows down. The slit flow does not flatten drops with diameter s at least ten-fold smaller than the slit gap. A comparison of the experime ntal data with the BEM 2-D simulation showed that:BEM provides good descrip tion of deformability. The effects of shear and elongation stress, the visc osity ratio, the drop diameter to channel gap ratio, the initial drop posit ion, the interfacial tension coefficient, and elasticity of the; dispersed phase were examined using the BEM. Simulation of flow through EFM was carri ed out using either FEM or Bindings theory. Both methods are suitable for c omputing the pressure losses and the stress fields. Analysis of now lines c an be used for optimization of the mixer's geometry.