Engineered transparent emulsion to optically study particulate flows in yield stress fluids

We have engineered a model suspension consisting of rigid particles and yield stress fluids. The suspending fluid is an emulsion with adjustable density, rheological behavior, and refractive index. We explain the design procedure in detail. The optically transparent emulsion opens the possibility of exploring particle tracking/image velocimetry (PIV/PTV) techniques in studying dynamic flows involving particles in complex fluids. As a proof of concept, we have performed PTV to provide accurate measurements of solid volume fractions for the dispersion of particles in a Taylor–Couette cell. Graphic abstract