Session A31: Porous Media Flows I - General

A comprehensive study of the lift generation in soft porous media under rapid compression

Lift generation in soft porous media under rapid compaction is a new concept for porous media flow, which has broad applications in biological systems, squeeze damping, and soft lubrication, etc. Previous studies on this topic share a common feature of neglecting the lift contribution of the undeformed porous structures surrounding the compressed porous media, thus deviated from real applications. Herein we report a comprehensive experimental and theoretical approach to treat this shortcoming. A soft, polyester, fibrous, porous material with specified micro-structure, porosity and permeability was dynamically compressed by a loaded piston in a porous-walled cylinder-piston apparatus. Pore air was forced out radially either directly to the ambient (``unconfined'' case) or to the surrounding undeformed porous media (``confined'' case). Detailed pressure measurements indicate that the air lifting force underneath the piston was enhanced by 25{\%} to 30{\%} for the ``confined'' case as compared to the ``unconfined'' case. A consolidation theory was developed to characterize this process, which shows very good agreements with the experimental data. This study significantly improves our understanding of the dynamic response of soft porous media under rapid compression.   

Characterisation of flux sensitivity to uncertainty in porous media

Natural porous media are typically heterogeneous on a range of length scales, and this leads to the challenge of defining effective medium properties with which estimates of fluid flow may be calculated. We develop a method to explore how the possible variability in the effective properties may impact estimates of the flow of a single phase fluid through a porous media. We use this method to explore how flow predictions are sensitive to uncertainty in the permeability field, and we develop the approach to explore how data may be used to reduce such uncertainty.   

Comparison of Experimental and Computational Methods in the Study of Flow in Porous Media

Both experimental and computational methods applied to the study of porous media flows are challenging due to the complex multi-phase geometry and ability to resolve scales over a reasonably large domain. This study compares experimentally obtained results based on refractive index matching of detailed velocity field vectors with those obtained using direct numerical simulations to evaluate both methods for consistency. Data were obtained in a randomly packed bed using uniformly sized spherical particles. Challenges associated with proper experimental methods including refractive index matching errors, magnification uncertainties, and the identification of the proper geometry are discussed. In addition the DNS challenges associated with, matching the geometry, grid resolution particularly near solid contact points , and proper boundary conditions are presented. Results are compared, with attention paid to identifying the relative uncertainty limitations based on the experimental and computational parameters for steady flow conditions within the bed.   

Micro-scale flow simulation and colloid transport modeling in saturated porous media

Adequate understanding of the mechanisms governing colloid retention by soil porous media is essential to the prediction and monitoring of the transport of contaminants through groundwater in the subsurface environment. This talk focuses on the representation of micro-scale flow and colloid-grain surface interactions in a computational approach with 3D porous media packed with glass beads. A corresponding 2D porous media is also developed to save some computational efforts. After solving the flow field with the Lattice Boltzmann method, a Lagrangian colloid tracking model is used to study the dynamics of colloidal particles considering Brownian force, hydrodynamic forces, and physicochemical forces. The attachment efficiency at favorable condition in our 3D model is compared with experimental data and also the efficiency predicted from other research group with different models. Under the unfavorable condition, the modeling and analysis of colloid transport will explore the effects of solution ionic strength on colloid reversible retention in both 2D and 3D models. To speed up our colloid tracking modeling, parallel implementation using Message Passing Interface (MPI) is performed and the related complexity analysis and scalability results will also be presented.   

Flow Intermittency, Dispersion, and Correlated Continuous Time Random Walks in Porous Media

We study the intermittency of fluid velocities in porous media and its relation to anomalous dispersion. The complexity of the pore scale flow arises from the heterogeneous medium structure that induces non-Gaussian velocity distributions, which can lead to a persistent non-Fickian dispersion. Lagrangian velocities measured at equidistant points along streamlines are shown to form a spatial Markov process. As a consequence of this remarkable property, the dispersion of fluid particles can be described by a continuous time random walk with correlated temporal increments. This new dynamical picture of intermittency provides a direct link between the microscale flow, its intermittent properties, and non-Fickian dispersion.   

SPH numerical simulation of fluid flow through a porous media

We have tested an improved a method for 3D SPH simulations of fluid flow through a porous media using an implementation of this method with the Dual-Physics code. This improvement makes it possible to simulate many particles (of the order of several million) in reasonable computer times because its execution on GPUs processors makes it possible to reduce considerably the simulation cost for large systems. Modifications in the initial configuration have been implemented in order to simulate different arrays and geometries for the porous media. The basic tests were reproduced and the performance was analyzed. Our 3D simulations of fluid flow through a saturated homogeneous porous media shows a discharge velocity proportional to the hydraulic gradient reproducing Darcy's law at small body forces. The results are comparable with values obtained in previous work and published in the literature for simulations of flow through periodic porous media. Our simulations for a non saturated porous media produce adequate qualitative results showing that a non steady state is generated. The relaxation time for these systems were obtained.   

Numerical Study of Usage Efficiency of Multistage Filters on Mineral Leaching Process

The numerical study of the usage efficiency of the multistage filters setting technology is carried out on the basis of mathematical simulation. And its application on in-situ mineral leaching process is considered. So long as mineral bearing sandstone in deposit mostly is separated by interbedded layers of sands and clays, it's expedient to use multistage filters setting technology at the mineral extraction. A comparison of the extraction degree at single and multistage filters is implemented. The results of calculations show that the distribution of flow (inflow) on well height is not uniform. In the calculations the well accepted as high-permeability channel, depending on the construction of the filter. Obtained results for a multistage filters setting qualitatively conform to the experimental findings. Wellbore is considered as a surface with a constant reduced pressure in the bottomhole formation zone. But such assumption does not show a qualitative picture of the fluid flow in the bottomhole zone [Brovin K.G., Grabovnikov V.A., 1997]. To construct an accurate mathematical model it's necessary to use Navier-Stokes equation for the interior of a vertical wellbore, and the filtration law for modeling the filtration in the reservoir. Strictly speaking, it would have had to sew two laws on the contact surface of a rock and filter. Such review requires enormous computing, as far as computational grid must be sufficiently thick to cover the interior of the wellbore.   

Dynamics of non- Newtonian fluid flow in porous media

We study the flow of a shear thinning polymer solution within a three dimensional model porous medium made of closely packed glass beads. The polymer solution is index matched with the glass so using confocal microscopy we are able to probe the dynamics of the flow at the pore scale in the bulk of the medium. We measure the fluid velocity field in the porous medium with particle image velocimetry technique. The probability distribution of the measured velocities has an exponential tail indicating the presence of large velocities compared to the average imposed velocity. The distribution of velocities also shows correlations with the pore size. We also compare the dynamics of the flow with the case of an additional immiscible fluid trapped within the medium. The probability distribution of velocities in the presence of residual trapped oil has a wider distribution as a result of the enhanced complexity of the medium.