In the microfluidic systems, the structure of micromixer is one of the important influence factors for the mixing performance. The traditional trial-and-error method for the optimization design of micromixer structure is difficult to consider both the mixing performance and power dissipation. Here we show the topology optimization method of designing the passive micromixer with the minimum power dissipation. The micromixer structure is updated with the adjoint method and adjoint variables are solved by the continuous adjoint equation derived manually. The forward fluid problem and adjoint equation are constructed using OpenFOAM. The optimal structure of micromixer is generated at different mixing index constraint and Re in two-dimensional design problem. Furthermore, in the three-dimensional optimal design, the multiple spiral slice structures are produced along the micromixer, which generate chaotic advection. This open-source topology optimization modeling framework is effective to design optimal structure of micromixer.

Chaotic flow inside porous media accelerates the transport, mixing, and reaction of molecules and particles in widespread natural and factitious processes. Current macroscopic models based on the average pore-scale variations show obvious limitations in the prediction of many chemical processes. In this paper, we reconstruct microscopic foam structures using Micro Computed Tomography to simulate fluid flow in structured ZSM-5@SiC foam catalyst. Moreover, we propose a conceptual model based on the microscopic mean square displacement theory to characterize the effective dispersion inside an open-cell foam. This model will explain the flow characteristics of confined fluid inside the porous media from fluid elements perspective. Particularly, dispersion factor and structure factor, as key parts of this model, perfectly interpret the driving characteristics of pressure drop, velocity different, and reaction in continuous foam media flow. This work also provides a unique means of predicting reaction kinetics of confined fluid in structured foam catalyst.

Open-cell foams as the column tray are promising candidates for the purpose of process intensification in the distillation process. In this paper, the real foam porous structure is obtained based on Micro Computed Tomography (µ-CT), and the bubble formation process on pore-scale foam tray is discussed based on the VOF-CSF model (volume of fluid method-continuous surface force). The results show that the wettability (CA), superficial gas velocity (Ug), porous structure, and clear liquid layer height (HCL) all affect a crucial factor of the foam tray - the liquid holdup in the porous channels (LHPC). It determines the effective porosity, which in turn affects the bubbling frequency and pressure drop. Meanwhile, the evolutionary mechanism of instantaneous pressure drop is analyzed based on the flow patterns, force analysis and interfacial phenomena. Moreover, the new model to predict pressure drop is proposed based on LHPC, which shows good consistency with experiments.