An investigation of the effect of viscosity on mixing in an oscillatory baffled column using digital particle image velocimetry and computational fluid dynamics simulation

In this paper, we examine the effect of viscosity on the performance of the oscillatory baffled column (OBC) using the digital particle image velocimetry (DPIV) technique and computational fluid dynamics (CFD) codes. A selection of Newtonian (1-210 cP) and shear thinning fluids is investigated. The effects of viscosity on mixing are carefully observed by analysing flow patterns generated by both the DPIV and CFD methods. A ratio of the plane-averaged axial over the radial velocity is defined to quantify such the viscosity effects. For the given geometry the velocity ratio approaches to 2 very quickly at increased oscillatory Reynolds numbers, regardless of the Newtonian and non-Newtonian fluids used. An empirical critical ratio of 3.5 is identified, below which the system mixes sufficiently. This would act as the guide for industrial applications where a viscous fluid is mixed in an aqueous solution in the OBC.