Abstract
The impetus of the current research is to use the direct simulation Monte Carlo (DSMC) algorithm to investigate fluid behaviour and gas transport in porous microchannels. Here, we demonstrate DSMC’s capability to simulate porous media up to 40% porosity. In this study, the porous geometry is generated by a random distribution of circular obstacles through the microchannel with no interpenetration between the obstacles. The influence of the morphology along with rarefaction and gas type on the apparent permeability is investigated. Moreover, the effects of porosity, solid particle’s diameter and specific surface area are considered. Our results demonstrate that although decreasing porosity intensifies tortuosity in the flow field, the tortuosity reduces at higher Knudsen numbers due to slip flow at solid boundaries. In addition, our study on two different gas species showed that the gas type affects slippage and apparent gas permeability. Finally, comparing different apparent permeability models showed that Beskok and Karniadakis model is valid only up to the early transition regime and at higher Knudsen numbers, the current data matches those models that take Knudsen diffusion into account as well.
Highlights
A grand research challenge in microscale porous media is to calculate the permeability of an unconventional reservoir, and Klinkenberg[8] was the first who set the tone by introducing apparent gas permeability and slippage factor
While still some modifications are needed for lattice Boltzmann method (LBM) to be used for microscale porous media[27], direct simulation Monte Carlo (DSMC) is capable of capturing the phenomena happening from the slip flow to free molecular regime
The gas flow in porous media is affected by two fundamental parameters
Summary
A grand research challenge in microscale porous media is to calculate the permeability of an unconventional reservoir, and Klinkenberg[8] was the first who set the tone by introducing apparent gas permeability and slippage factor. The results demonstrated that the difference between apparent permeability and intrinsic permeability increases by decreasing in pore size or pore pressure In another attempt, Zhao et al.[16] investigated the effect of heterogeneity in porous media showing that for small Knudsen number, gas mainly flows through the large pores. Regarding that and despite the fact that DSMC still struggles with relatively high computational cost, many researchers have challenged this point of view and extended the application of DSMC by employing this approach to a broad set of microscale systems This was accomplished with the help of certain measurements, such as new collision schemes, which addressed this issue[25]. The effect of critical parameters in a porous media such as porosity, particle’s diameter specific surface area and gas type on flow behavior, including velocity profile, apparent gas permeability, and mass flow rate are investigated
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