The Effect of the Layered Internal Structure of Fibrous Beds on the Hydrodynamic Diffusive Behavior of Microparticles

To separate and collect microparticles such as cells, the behavior of particles in fibrous filters was investigated. It is essential to understand, in detail, the motion of particles in microscale flows, because Re is often small, and particles exhibit complex behaviors such as changes in relative position and spreading owing to hydrodynamic interactions. We calculated the motion of microparticles passing through the fibrous bed using the Stokesian dynamics method, in which hydrodynamic interaction is considered, theoretically. The fibrous bed was modeled by particles and five types of structures (a monolayer with fiber volume fractions ϕ of 3%, 4%, and 5%, and a bilayer with ϕ = 3−5% and 5−3%) were considered. Our numerical results showed that the particles moved in a complicated manner, and spread throughout the fibrous bed. It was found that the behavior of individual microparticles varied depending on the internal structure, although the average permeation velocity was primarily determined by the fiber volume fraction. This great dependence of the behavior of particle assemblage on the internal structure of the fibrous bed was caused by the individual particle motion under the influence of the layers in front of and behind them, owing to the hydrodynamic interaction.

Reconfigurable microfluidics: real-time shaping of virtual channels through hydrodynamic forces

Virtual microfluidic channels, formed through hydrodynamic focusing within a 2D flow cell, enable the dynamic implementation of key microfluidic functionalities, such as the precise guiding, splitting, merging and mixing of microscale flows.

Parametric Study of Rarefaction Effects on Micro- and Nanoscale Thermal Flows in Porous Structures

Hydrodynamics and heat transfer in micro/nano channels filled with porous media for different porosities and Knudsen numbers, Kn, ranging from 0.1 to 10, are considered. The performance of standard lattice Boltzmann method (LBM) is confined to the microscale flows with a Knudsen number less than 0.1. Therefore, by considering the rarefaction effect on the viscosity and thermal conductivity, a modified thermal LBM is used, which is able to extend the ability of LBM to simulate wide range of Knudsen flow regimes. The present study reports the effects of the Knudsen number and porosity on the flow rate, permeability, and mean Nusselt number. The Knudsen's minimum effect for micro/nano channels filled with porous media was observed. In addition to the porosity and Knudsen number, the obstacle sizes have important role in the heat transfer, so that enhanced heat transfer is observed when the obstacle sizes decrease. For the same porosity and Knudsen number, the inline porous structure has the highest heat transfer performance.