Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
15
8
2012
COMPARISON OF TWO PERMEATION TEST BENCHES AND TWO DETERMINATION METHODS FOR DARCY'S AND FORCHHEIMER'S PERMEABILITIES
The thermal load protection of hypersonic and space vehicle structures can be achieved by either passive or active methods, such as ablative materials or active cooling. For the latter, porous Ceramic Matrix Composite media offer a possibility to exploit thermal protection by means of transpiration cooling. One of the related key issues is the estimation of permeability parameters such as Darcy's and Forchheimer's terms. The present paper aims at proposing an analytical and applied comparison of two determination methods (one based on the International Standard Organisation (ISO) norm 4022 and one derived for compressible flows, the so-called P 2 method). To apply these mathematically equivalent laws, a cross verification and validation has been carried out on two different test rigs with different porous media (metallic and composite) with a range of Darcian permeability varying from 10−17 m 2 to 10−11 m 2. The French PRISME laboratory test bench has a higher accuracy for thin samples (under 3 mm), while the German Aerospace Center (DLR) rig is more adapted to thick samples (over 3 mm). The results are judged to be satisfactory (discrepancy around 14% for reference samples). The methods used to post-process the data can generate discrepancies up to a factor of2 for a given set of experimental data.
Nicolas
Gascoin
PRISME Laboratory, INSA-Centre Val de Loire, 88 boulevard Lahitolle, 18000 Bourges, France
Guillaume
Fau
PRISME Laboratory, INSA-Centre Val de Loire, 88 boulevard Lahitolle, 18000 Bourges, France
Philippe
Gillard
PRISME, IUT Bourges, 63, avenue de Lattre de Tassigny, 18000 Bourges, France
Markus
Kuhn
German Aerospace Center, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany
Marc
Bouchez
MBDA-France, 18 rue Le Brix, 18000 Bourges, France
Johan
Steelant
Section of Aerothermodynamics ESTEC-ESA, P.O. Box 299, 2200 AG Noordwijk, The Netherlands
705-720
TIME DEPENDENCE OF FREE FALL GRAVITY DRAINAGE IN UNCONSOLIDATED SAND
The time dependence of the gravity drainage of brine through a water wet porous medium has been examined experimentally using continuous resistance measurements in three 1 m columns packed with sand. Analysis of the resulting data showed that water saturation at any particular location had a power law dependence on time. This was shown to be consistent with gravity-dominated drainage and the fact that the water relative permeability can be described by the Corey parameterization. This confirmed earlier analyses which showed that gravity-dominated drainage should have a power law dependence on time.
Stefan
Iglauer
Department of Earth Science and Engineering, Imperial College London, Prince Consort Road, London SW7 2BP, UK
Ann H.
Muggeridge
Department of Earth Science and Engineering, Imperial College London, United Kingdom
721-733
ADEQUACY OF SURFACE DIFFUSION MODELS TO SIMULATE NONEQUILIBRIUM MASS TRANSFER IN SOILS
Diffusion from intra-particle pore spaces is considered to be the main reason for the slow release of contaminants from soil. Diffusion-controlled mass transfer can be simulated by the homogeneous surface diffusion model (HSDM). The objective of this paper is to present a simplified HSDM model (SHSDM) and a finite element HSDM model (FEHSDM) to simulate advective-dispersive transport through soils, coupled with intra-particle diffusion, under nonequilibrium conditions and compare these models with the dispersed flow, film and particle diffusion model (DF-FPDM) that has recently been reported in literature. The FEHSDM predictions compare well with experimental data for slightly hydrophobic compounds. The SHSDM and the DF-FPDM predictions, on the other hand, compare well with experimental results for relatively hydrophobic compounds. The SHSDM and the DF-FPDM predictions are practically the same for mass transfer Biot numbers Bi ≥ 20. However, considerable difference in the predictions of these two models is observed for Bi ≤ 1. The SHSDM and the DF-FPDM, by and large, provide convergent results and remain stable for Peclet numbers Pe ≤ 2.5 and Courant number Cr ≤ 1.0, with the FEHSDM requiring finer spatial and temporal discretizations.
Nazmul
Hasan
Civil and Environmental Engineering, Washington State University, Richland, WA 99354
Md. Akram
Hossain
Civil and Environmental Engineering, Washington State University, Richland, Washington 99354
735-744
ANALYTICAL STUDY OF LINEAR AND NONLINEAR DOUBLE DIFFUSIVE CONVECTION IN A ROTATING ANISOTROPIC POROUS LAYER WITH SORET EFFECT
A linear and nonlinear stability analysis of double diffusive convection in a rotating horizontal anisotropic porous layer with Soret effect has been performed. The linear theory is based on the usual normal mode technique and the nonlinear theory on the truncated Fourier series analysis. The Darcy model extended to include time derivative and Coriolis terms with anisotropic permeability is used to describe the flow through porous media. The effect of rotation, mechanical and thermal anisotropy parameters, Darcy-Prandtl number, solute Rayleigh number, Lewis number, normalized porosity and Soret parameter on the stationary and overstable convection is discussed. A finite amplitude analysis is performed to find the thermal and Sherwood numbers. The effect of various parameters on heat and mass transfer is also investigated.
S . N.
Gaikwad
Department of Mathematics, Gulbarga University, Jnana Ganga, Gulbarga-585106, India
Shaheen
Kouser
Department of Mathematics, Gulbarga University, Jnana Ganga, Gulbarga-585106, India
745-761
DOUBLE DIFFUSIVE CONVECTION IN A POROUS CAVITY NEAR ITS DENSITY MAXIMUM
Natural convection of cold water around its density maximum in two-dimensional cavity filled with a water-saturated isotropic porous medium is studied numerically. The horizontal walls of the cavity are insulated. The opposing vertical walls are kept at different temperatures θh and θc (θh > θc). The concentration levels at the cold wall and the hot wall are respectively Cc and Ch with Ch > Cc. The governing equations are solved by the finite volume method using the SIMPLE (semi-implicit method for pressure linked equation) algorithm with the QUICK scheme of Hayase et al. The results are presented in the form of streamlines, isotherms, isoconcentrations and mid-height velocity profiles for various values of thermal Rayleigh number, density inversion parameter, buoyancy ratio, Schmidt number, Darcy number and porosity. In addition, results for the average Nusselt number and Sherwood number are presented and discussed for various parametric conditions. It is observed that the Nusselt number and the average Sherwood number behave nonlinearly with increasing buoyancy ratio number.
M.
Muthtamilselvan
Department of Applied Mathematics, Bharathiar University, Coimbatore-641 402, India
Manab Kumar
Das
Indian Institute of Technology (IIT), Kharagpur, 721302, West Bengal, India
765-774
A GENERAL FORMULA FOR CAPILLARY SUCTION-PRESSURE IN POROUS MEDIA
Imbibition or injection of a liquid into a porous medium is often modeled as a fully saturated flow behind a clearly defined liquid front. In such a quasi-steady moving-boundary problem, the capillary pressure is needed as a pressure boundary condition on the liquid front to pull the front along during such an imbibition/injection process. A simple, general formula has been developed for the capillary suction-pressure in porous media, which relates the capillary pressure to the microstructure of various porous media. The energy-balance principle is applied during the wicking process to develop this expression for the capillary pressure in a general porous medium. The proposed formula can be applied to both the homogeneous as well as inhomogeneous porous media. To validate the suggested theory, six different cases of the capillary pressure from the literature are considered. It is shown that the new formula leads to an identical expression for the capillary pressure for each of the studied cases. The proposed equation can also be used to estimate the capillary pressure from the micrographs of a porous medium.
Reza
Masoodi
Assistant Professor
Krishna M.
Pillai
Laboratory for Flow and Transport Studies in Porous Media, Mechanical Engineering, University of Wisconsin-Milwaukee, 3200, N. Cramer Street, Milwaukee, Wisconsin 53211, USA
775-783
FEEDBACK CONTROL OF FLOWS IN A POROUS SQUARE ENCLOSURE HAVING NONUNIFORM INTERNAL HEATING
The COMSOL Multiphysics software was used to study numerically the effect of feedback control on convective flow within a square region filled with a fluid-saturated porous medium. The left side wall is heated and the right side wall is cooled, while the horizontal walls are kept adiabatic. Heat is generated internally within the porous medium at a rate proportional to a power of the temperature difference. The Darcy model is used in the mathematical formulation for the porous layer. A sensor array is embedded at the fluid's mid-width enclosure and actuators are located on the heating side. It was found that the flow intensity and the space average within the convective region can be suppressed by the feedback control.
H.
Saleh
Centre for Modelling & Data Analysis, School of Mathematical Sciences, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor, Malaysia
Z.
Mustafa
Centre for Modelling & Data Analysis, School of Mathematical Sciences, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor, Malaysia
I
Hashim
Rozaini
Roslan
Center for Research in Computational Mathematics, Faculty of Science, Technology and Human Development, Universiti Tun Hussein Onn, 86400 Batu Pahat, Johor DT, Malaysia
785-792
NUMERICAL SIMULATION OF TRANSIENT MOISTURE TRANSPORT FOR HYGROSCOPIC INERTIA ASSESSMENT
The finishing layers of walls and ceiling may be important contributors to a room's hygroscopic inertia and therefore reduce peak values of relative humidity variation. The precise hygric simulation of the surface layers can be important for improving the design of these building elements. This paper reports the results from systematic simulation of a set of dynamic experiments of transient moisture transfer in the hygroscopic region using HAM-Tools software. The authors use a set of laboratory experiments to verify and correct the modelling assumptions and the basic data used in simulations, to select the most effective strategies for conducting this type of simulation. Previous standard measurements of sorption isotherms and vapor permeability for gypsum-based revetments and applied coatings provided basic material data for numerical simulations. Two types of simulations of actual laboratory tests were then performed: (1) Moisture Buffer Value (MBV) tests for validation of material modelling and (2) flux chamber tests for validation of room air and material coupling. As a means of bringing these concepts closer to practice, the generalization of a daily hygroscopic inertia index application in a simple assessment method is improved and supported by the latter simulations.
Nuno M. M.
Ramos
Laboratório de Física das Construções (LFC), Departamento de Engenharia Civil, Universidade do Porto
Angela Sacic
Kalagasidis
Chalmers University of Technology, Dep. Of Building Physics, S-412 96 Guteborg, Sweden
V. P.
de Freitas
CONSTRUCT-LFC, Departamento de Engenharia Civil, Universidade do Porto Rua Dr. Roberto Frias, s/n; 4200-465 Porto, Portugal
J.M.P.Q.
Delgado
CONSTRUCT-LFC, Departamento de Engenharia Civil, Universidade do Porto Rua Dr. Roberto Frias, s/n; 4200-465 Porto, Portugal
793-804