(35b) Mixing Viscous Fluids Using a Reconfigurable Split-and-Recombine Static Mixer

Mixing of highly viscous materials at low Reynolds numbers can be achieved by stretching and folding motions. Pure shear flow can achieve a stretching motion that grows approximately linearly with time. Extensional flows, on the other hand, are potentially more effective due to the exponential stretching in time of fluid elements. Split and recombine (SAR) static mixers employ extensional flow by rearranging fluid into stacks of layers which duplicate after each mixing stage. The use of a SAR mixer is proposed for homogeneous dispersion of small amounts of material into a highly viscous fluid. A prototype was constructed by stacking a series of thin channel cross sections, which are easily constructed from sheets of material and can be rearranged for optimization and design purposes. We discuss the characterization of the mixer performance regarding flow patterns, pressure drop and mixing quality via numerical simulations and magnetic resonance imaging experiments.