01. Experimental/Computational Fluid Dynamics

In laminar regimes, increasing the liquid-liquid interfacial area where the molecular diffusion occurs, is crucial for enhancing mixing performance. The interfacial area exponentially increases by applying operations that fold and stretch fluid elements. An oscillatory baffled reactor (OBR) is a tubular reactor in which baffles are placed at equal intervals, where fluid mixing occurs due to the interaction between baffles and oscillatory flow. In regions where the oscillatory Reynolds number, Reo, defined with the maximum velocity of the oscillatory flow, is low, mixing by folding and stretching of fluid is observed in each baffle section. In this study, numerical simulation and experimental methods were employed to analyze and evaluate mixing performance based on the folding and stretching of the fluid in the OBR. The OBR had an inner diameter of 13 mm, baffle intervals of 20 mm, and baffles with an orifice of an open area ratio of 25% of the OBR cross-sectional area were used. The Reo was kept at 29, and the stroke ratio to the baffle interval varied from 0.65 to 1.3. OpenFOAM (OpenCFD Ltd.) was used for numerical simulation assuming axisymmetric flow. Boundary lines were obtained by tracing virtual particles, first arranged in a line at the orifice, and the distances between them were summed sequentially to calculate the length of the boundary line. The boundary area was calculated by rotating it about the axis center. In experiments, a glycerin solution with the same viscosity and Reo as the simulation was prepared. The boundary area was colored with Rhodamine, then placed in a membrane-like configuration at the orifice. As subjected to oscillatory flow, the increasing-colored line was visualized by fluorescing under a laser sheet. In simulations, the interfacial area increased exponentially, and the shape of the boundary line at this time closely matched in experiments.

Dr.

Satoko Fujioka