Volume 19, Issue 1, 2010

DESIGN AND EVALUATION OF AN IDEALIZED POROUS MEDIUM FOR CALIBRATION OF PERMEABILITY MEASURING DEVICES

Andrew P. Vechart , Reza Masoodi and Krishna M. Pillai*

Laboratory for Flow and Transport Studies in Porous Media, Department of Mechanical Engineering, University of Wisconsin-Milwaukee, EMS, 3200 N. Cramer St., Milwaukee, WI 53211, USA
http://www4.uwm.edu/porous/
Currently pursuing M.Sc. in Computation for Design and Optimization Program at M.I.T.

*Author to whom correspondence should be addressed, e-mail: krishna@uwm.edu

ABSTRACT
Calibration of permeability measuring devices or experimental setups remains an important concern of the flow modeling community of LCM processes (the set of technologies, including RTM and VARTM, that are used for manufacturing polymer composites) since the fidelity of any mold-filling simulation depends on the accuracy of fiber-mat permeability measured through experiments. The design and evaluation of a new cost-effective and accessible calibration-tool for use in both 1-D and radial flow set-ups used in the permeability evaluation experiments is presented here. The tool, comprising of a lattice-like structure patterned out of a repeating unit-cell and based on the design proposed by Morren et al. [9], represents an idealized porous medium of known permeability that can be used for such calibrations. Stereolithography technique was used to manufacture the tool out of a plastic to fine tolerances. Computational fluid dynamics (CFD) simulations were then performed in the unit cell to evaluate the principle permeabilities of the idealized porous medium. Thereafter, the proposed calibration tool was used in our experimental apparatus to evaluate the accuracy of our permeability measurements. The tool was used for the estimation of accuracy of four different methods: the transient and steady-state tests for the 1-D flow device, and the transient and steady-state tests for the radial flow device. Results show close agreement between the permeabilities estimated through experiments and the permeabilities estimated from the CFD simulation. The study thus establishes the usefulness of the idealized porous medium for calibrating permeability measuring devices.

Keywords: calibration, permeability, permeability measurement, mold-filling, LCM, RTM, VARTM, 1-D flow, radial flow, Darcy’s law.