Flow Pattern and Mixing Characteristics of Highly Viscous Fluids in a Dynamic Mixer

Computational fluid dynamics (CFD) was used to assess the flow patterns and mixing characteristics of highly viscous fluids in a dynamic mixer. The simulated concentration distribution was validated by the data measured using planar laser-induced fluorescence (PLIF). The refractive indices of the two fluids and the transparent solid material comprising the mixer were matched to minimize the bending of sent and received light. The simulated concentration fields agreed well with the measured concentration fields. The flow pattern and mixing performance were quantitatively evaluated by using the mixing index λ and the coefficient of variation (COV), respectively. After the mixing performance reached time independence, a reduction of the COV at the outlet was associated with a slight increase of the volume-averaged |λ|. The results suggested that elongational flow was more effective than shear flow in obtaining a more uniform concentration distribution in highly viscous fluids.