Sharif Digital Repository

In this paper we present new methods to estimate the effective permeability (keff) of heterogeneous porous media with a wide distribution of permeabilities and various underlying structures, using percolation concepts. We first set a threshold permeability (kth) on the permeability density function and use standard algorithms from percolation theory to check whether the high permeable grid blocks (i.e., those with permeability higher than kth) with occupied fraction of “p” first forms a cluster connecting two opposite sides of the system in the direction of the flow (high permeability flow pathway). Then we estimate the effective permeability of the heterogeneous porous media in different... 

Multiscale finite volume (MSFV) method have been developed and applied in various complicated physics. The most important advantage of MSFV method is its computational efficiency. In this paper we present a new set of boundary condition for calculation of basis and correction functions which leads to further reduction in computational time in problems with medium heterogeneity and therefore improves computational efficiency. In standard MSFV (sMSFV) method reduced boundary condition is used to determine the basis and correction functions which is based on local information, however in modified MSFV (mMSFV) method global information is used at initial time for constructing boundary condition... 

In this study, a two-stage membrane system for the separation of CH4/CO2 was designed based on a series of laboratory-scale experiments obtained using two types of commercial hollow fiber membranes including polyphenylene oxide (PPO) and Cardo-type polyimide (PI). The former showed high permeability and low to moderate selectivity, while the latter exhibited high selectivity and moderate permeability. In this design, the permeate from the first stage - rich in CO2 but containing considerable amount of methane - is fed into the second stage to recover its methane content. The performances of double- and single-stage system designs were compared in terms of methane loss (the ratio of methane... 

In this article, transient hydrodynamic and heat-transfer behavior of Newtonian fluid flow in vertical parallel-plate channels partially filled with a porous medium has been investigated numerically. In this regard, the influences of macroscopic local inertial term and the viscous heating due to the viscous dissipation were taken into account in the momentum equations of porous region and the thermal energy equations, respectively. Moreover, Forchheimer-Brinkman extended Darcy model was used to model fluid flow in the porous region. In addition, an analytical solution was obtained in the case of negligible Brinkman and Forchheimer number values at the steady-state conditions. The predicted...