Refractive Index-Matched PIV Experiments and CFD Simulations of Mixing in a Complex Dynamic Geometry

Abstract

The flow fields under laminar conditions in two typical regions of a cavity transfer dynamic mixer consisting of an inner rotor and outer stator were visualized by refractive index (RI) matched particle image velocimetry (PIV) experiments. The RI of the working liquids and the transparent solid parts of rotor and stator were matched to allow for unobstructed optical access. The flow fields were predicted by using computational fluid dynamics (CFD) simulations including models for species transport. Various flow patterns in the dynamic mixer are discussed. The simulated flow fields in the two investigated regions agree well with the experimental data. The effect of gap width between rotor and stator (σ) on the scalar mixing was evaluated, and smaller σ will achieve better mixing because of the enhanced shearing and higher energy consumption.

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

“…To quantitatively assess the disparity between the experimental data and simulated results, concentration profiles are presented in Figure 5 In addition, simulated concentration profiles with different grids are shown in Figure 5. As we reported in our previous work, 8 the concentration field exhibits greater sensitivity to cell spacing than the velocity field. A smaller cell size results in a more precise simulated concentration distribution.…”

“…This paper extends our earlier research on mixing highly viscous fluids in dynamic mixers . Unlike the previous paper that used PIV experiments for validation, our current study presents scalar concentration distribution data measured with PLIF, providing a direct demonstration of scalar mixing.…”

“…11 This paper extends our earlier research on mixing highly viscous fluids in dynamic mixers. 8 Unlike the previous paper that used PIV experiments for validation, our current study presents scalar concentration distribution data measured with PLIF, providing a direct demonstration of scalar mixing. In earlier studies conducted within the dynamic mixer, the focus was on exploring the influence of buoyancy, originating from fluids with different densities, on the mixing performance.…”

“…Their study underscored the significant impact of factors, such as the geometric dimensions of cavities and an optimal ratio, defined as the axial and tangential velocity of the fluid, on the mixing performance of the CTM. Huang et al 8 simulated the mixing process of Newtonian viscous fluids, assessing how the clearance between the rotor and stator influences mixing performance. Their findings suggested that a smaller gap improves mixing but results in higher energy consumption.…”

Study of hydrodynamics and flow characteristics in a twin‐blade planetary mixer with non‐Newtonian fluids

“…The temporal discretization scheme was first‐order implicit since it is unconditionally stable with respect to the time‐step size. Although the Courant number was not required to be small to ensure stability for the implicit scheme, to resolve the transient details accurately, the time step Δ t was set to 0.001 s to keep the Courant number ( U Δ t /Δ x ) less than unity, and thus the fluid particle did not move more than one grid length in a single time step 45–47 . A Supermicro workstation equipped with 20 Intel(R) Xeon(R) CPU E5–2640 v4 @ 2.40 GHz and 96 GB of RAM was used to run the simulations, and the simulation time of each case was about 39 h. The convergence criterion of each governing equation was set to 10 −5 to ensure simulation accuracy.…”