Search results for "POROUS-MEDIA"
showing 3 items of 3 documents
Modeling mass transfer in fracture flows with the time domain-random walk method
2019
The time domain-random walk method was developed further for simulating mass transfer in fracture flows together with matrix diffusion in surrounding porous media. Specifically, a time domain-random walk scheme was developed for numerically approximating solutions of the advection-diffusion equation when the diffusion coefficient exhibits significant spatial variation or even discontinuities. The proposed scheme relies on second-order accurate, central-difference approximations of the advective and diffusive fluxes. The scheme was verified by comparing simulated results against analytical solutions in flow configurations involving a rectangular channel connected on one side with a porous ma…
Subsecond pore‐scale displacement processes and relaxation dynamics in multiphase flow
2014
With recent advances at X‐ray microcomputed tomography (μCT) synchrotron beam lines, it is now possible to study pore‐scale flow in porous rock under dynamic flow conditions. The collection of four‐dimensional data allows for the direct 3‐D visualization of fluid‐fluid displacement in porous rock as a function of time. However, even state‐of‐the‐art fast‐μCT scans require between one and a few seconds to complete and the much faster fluid movement occurring during that time interval is manifested as imaging artifacts in the reconstructed 3‐D volume. We present an approach to analyze the 2‐D radiograph data collected during fast‐μCT to study the pore‐scale displacement dynamics on the time s…
Validity of NMR pore-size analysis of cultutal heritage ancient building materials containing magnetic impurities
2007
NMR relaxation time distributions, obtained with laboratory and portable devices, are utilized to characterize the pore-size distributions of building materials coming from the Roman remains of the Greek-Roman Theatre of Taormina. To validate the interpretation of relaxation data in terms of pore-size distribution, comparison of results from standard and in situ NMR experiments with results of the mercury intrusion porosimetry (MIP) has been made. Although the pore-size distributions can be obtained by NMR in terms of either longitudinal (T-1) or transverse (T-2) relaxation times distributions, the shorter duration of the T-2 measurement makes it, in principle, preferable, although the dete…