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Séminaire K. Pillai

26 juin 2012

vendredi 29 juin a 14h

Salle Castex RDC.

K. M. Pillai, Ph.D. - Associate Professor

Laboratory for Flow and Transport Studies in Porous Media - Department of Mechanical Engineering

University of Wisconsin-Milwaukee (USA)

Part 1 Title : Drying Simulation of a Porous Medium Using a Pore-Network Model with Multiple Open-Sides


Pore-network models are employed frequently to study drying in porous media as they, unlike continuum approaches, provide insight into the pore-scale phenomena prevalent during the drying process. Drying characteristics of a pore-network with two open sides are investigated numerically after ignoring gravitational and viscous forces as well as the liquid-film effects. The invasion percolation (IP) algorithm is applied to simulate the convective capillary slow-drying under isothermal conditions. The drying characteristics of such a network have been compared with those of the same pore-network with only one open side to the air (the case typically studied in the literature). The obtained results for this novel configuration show that the exposed surface of the network with two open sides remains wet longer than that of the network with only one exposed surface. Consequently, mass flow rates for the network with two open sides are much higher than those of the other network and therefore, the network with two open sides dries much faster than network with one open side. The study yields some new insights into the evaporation dynamics of networks with multiple open sides.

Part 2 Title : Experimental and Theoretical Validation of permeability obtained using the closure formulation for sintered polymer wicks

Abstract :

Characterization of permeability remains one of the most important problems in studies on flow and transport in porous media. Several models have been proposed in the literature, where the effect of porous-medium microstructure is overlooked and the permeability is estimated as an analytical function of porosity and grain/fiber size. Such models either assume simple internal structures or are based on empirically verified correlations. In the present work, the closure formulation based on the Darcy’s law derivations of Whitaker is utilized and the permeability tensor is estimated for a porous wick composed of random-shaped micron-sized beads. A 2D micrograph prepared by scanning electron microscope (SEM) is used, and the closure problem is solved numerically in the void region of a unit cell considered in the sample by using COMSOL Multiphysics software. Size of an optimum unit cell is estimated through a convergence study. Results are compared with the experimental data obtained from a Falling Head Permeameter as well as the direct Stokes-flow simulations and the theoretical/empirical permeability models.