h i g h l i g h t s Numerical simulation of mixing in a human duodenum featuring circular folds. Tracking evolving concentration and mixing level distributions under segmentation. Mixing intensification by prominent vortices with high velocity and shear rate. Promoting mixing by tall and slim folds with enlarged segmentation amplitude, frequency and wavelength.

The enzymatic reaction system with a solid−liquid−gas three-phase interface microenvironment allows oxygen to be directly supplied to the oxidase catalytic reaction from the gas phase, effectively improving enzyme kinetics as compared with the conventional two-phase system. For this new system, a mathematical model is developed in this work to describe the enzymatic reaction coupled with interphase mass transfer, by which the influences of three-phase interfacial microenvironment on reaction kinetics can be systematically and quantitatively explored. The numerical simulations reveal that the flux of oxygen transport across the interface between the gas phase and the enzyme layer dominantly determines the H 2 O 2 production rate. The porous substrate possessing larger porosity and smaller pores, when coated with a thick and concentrated enzyme layer, can potentially lead to higher oxygen supply and hence a higher H 2 O 2 production rate. Moreover, regardless of the pore diameter, the H 2 O 2 production rate remains constant after the porosity is greater than 0.8, and if the enzyme concentration is not less than 5 mol m −3 , the H 2 O 2 production rate no longer changes after the thickness of the enzyme layer is greater than 0.5 μm. This work offers a powerful in silico tool for the investigation of the three-phase enzymatic reaction system. The quantitative results and mechanistic findings will lead to optimized design of this promising system.

Tremendous efforts have been devoted to the modeling of droplet deposition on smooth and patterned surfaces with ordered structures. However, systematic work focusing on randomly rough surfaces, which are the most common bare substrate surfaces, can be hardly identified. A phase field modeling method together with a unique analysis approach has been developed in this work to characterize single droplet deposition on randomly rough surfaces. It is interesting to observe that the droplet shape evolves quite differently on a randomly rough surface, as compared to a patterned surface, even if two surfaces have the same roughness. Parametric studies have been carried out to explore how the morphological metrics of randomly rough surfaces, which include the Wenzel roughness parameter (W r ) and the root-mean-square roughness (R r ), can affect droplet impact dynamics. The quantitative relationships derived from this study can eventually shed light on droplet shape on-aim control during the deposition process, which is of great practical importance in many applications.

Bionics is a fascinating subject that has inspired many inventions through learning from biological structures and functions. In this work, a coupled multi-physics model has been developed to characterize ocular water evaporation with realistic eyelash structures taken into account. From a chemical engineering perspective, the protective function of human eyelashes in terms of evaporation inhibition has been rationally revealed. Systematic investigations were carried out to elucidate the effects of different eyelash lengths, orientations and inlet air directions on water evaporation on the ocular surface. The results clearly demonstrate that regardless of inlet air directions and eyelash orientations, increasing eyelash length from zero to an optimal length can effectively reduce water evaporation. However, further increase in the eyelash length can lead to enhanced evaporation. For the normal and parallel inlet air directions, the optimal eyelash length is around 15–30% of the eye width and can offer approximately 10–30% evaporation reduction when compared with the cases without eyelashes. These values are independent of the eyelash orientation. This investigation provides valuable data for in-depth understanding of the protective function of the eyelashes, which can be used in the future to improve and optimize bionic designs inspired by human eyelashes.

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