Mixing of miscible shear-thinning fluids in a lid-driven cavity

The concentration and velocity fields of two refractive index matched miscible shear-thinning fluids in a lid-driven cavity were investigated by using planar laser-induced fluorescence and particle image velocimetry,as well by computational fluid dynamics.Quantitative analyses show that the results obtained by flow simulations with the species transport model are in good agreement with the experimental results.The effects of different parameters were studied by using the intensity of segregation.For two fluids with the same rheological parameters,the relative amounts of liquids H_(1)/H and the power-law index n dominate the mixing process while the Reynolds number Re plays a marginal role.As for two fluids with density difference,buoyancy has significant influence on the mixing process.The dimensionless group Ar/Re(redefined such as to include shear thinning behavior)is proposed for assessing the effect of buoyancy and rheological properties on the mixing of miscible shear-thinning fluids.

Numerical study of short-circuiting flow and particles in a gas cyclone

Short-circuiting flow is an important secondary flow in gas cyclones, which has a negative impact on the separation performance. To improve the understanding of the short-circuiting flow and guide the optimization of gas cyclones, this paper presents a numerical study of a cyclone using computational fluid dynamics. Based on the steady flow field, three methods were adopted to investigate the formation mechanism and characteristics of the short-circuiting flow and particles. The temporal variation of the tracer species concentration distribution reveals that the formation mechanism of the short-circuiting flow is the squeeze between the airflows entering the annular space of the gas cyclone at different times. The short-circuiting flow region, distinguished through the spatial distribution of the moments of age, is characterized by a small mean age and a large coefficient of variation. The proportion of the short-circuiting particles increases with the increase of the inlet velocity only for small particles. But with the increase of particle size, the proportion of the short-circuiting particles decreases faster at higher inlet velocities, resulting in significant differences in collection efficiency curves.

Addressing Transport Issues in Non‑Aqueous Li–air Batteries to Achieving High Electrochemical Performance

Li–air batteries are a promising type of energy storage technology because of the ultra-high theoretical specific energy.Great advances are made in recent years,including the illustration of reaction mechanisms,development of effective catalyst materials,and design of battery structures accelerating species transport.However,the application still suffers from low rate capability,poor round-trip efficiency,and unsatisfactory cycling life.Herein,we mainly focus on the species transport issues of non-aqueous Li–air batteries,including Li^(+) across the solid surfaces and the electrolyte,O_(2)solubility and diffusivity,distribution of intermediates and products,and side reactions by other components from the air.Besides,considerable emphasis is paid to expound the approaches for enhancing species transport and accelerating reactions,among which the realization of well-designed electrode structures and flowing electrolytes is of great significance for the rapid migration of O_(2)and Li^(+)and mitigating the negative effects by solid insoluble Li_(2)O_(2).Moreover,optimizing reaction interfaces and operating conditions is an attractive alternative to promote reaction rates.This work aims to identify the mechanism of transport issues and corresponding challenges and perspectives,guiding the structure design and material selection to achieve high-performance Li–air batteries.