We study gas diffusion through computer-generated random fibre networks using random walk simulations. The simulation results are consistent with steady-state experiments. The comparison of the simulated time-dependent diffusion flux with one-dimensional diffusion theory suggests that the latter is invalid at low porosities and low thicknesses. We also find that, if sorption is relevant, steady...

The transverse permeability for creeping flow through unidirectional random arrays of fibers/cylinders has been studied numerically using the finite element method (FEM). A modified Carman-Kozeny (CK) relation is presented which takes into account the tortuosity (flow path) and the lubrication effect of the narrow channels. The proposed relation is valid in a wide range of porosities compared t...

We study the permeability of quasi-two-dimensional porous structures of randomly placed overlapping monodisperse circular and elliptical grains. Measurements in microfluidic devices and lattice Boltzmann simulations demonstrate that the permeability is determined by the Euler characteristic of the conducting phase. We obtain an expression for the permeability that is independent of the percolat...

Periodic structures with extremely low porosities capable of forming large band gaps-frequency ranges with strong wave attenuation-are designed by patterning an elastic sheet with an array of alternating crack-like pores separated by small ligaments. The results indicate that the presence and size of the band gaps are controlled by the smallest geometric -feature in the system (which can be eas...

Defect formation is a common problem in selective laser melting (SLM). This paper provides a review of defect formation mechanisms in SLM. It summarizes the recent research outcomes on defect findings and classification, analyzes formation mechanisms of the common defects, such as porosities, incomplete fusion holes, and cracks. The paper discusses the effect of the process parameters on defect...

Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite e...

Flow fields around reformed earth embankment windbreak walls (REEWWs) with five different porosities under crosswind were studied using the improved delayed detached eddy simulation (IDDES) based on SST ?-? turbulence model by computational fluid dynamics (CFD) in this paper. Based simulated flow field results, finite element method (FEM) was adopted to analyze wind-induced displacement of cate...

Sound propagation in water-saturated granular sediments is known to depend on the sediment porosity, but few data in the literature address both the frequency and porosity dependency. To begin to address this deficiency, a fluidized bed technique was used to control the porosity of an artificial sediment composed of glass spheres of 265 μm diameter. Time-of-flight measurements and the Fourier p...