COMSOL Multiphysics^® 5.5 Release Highlights

Porous Media Flow Module

COMSOL Multiphysics^® version 5.5 introduces the new Porous Media Flow Module. This add-on module allows you to model mass, momentum, and energy transport in porous media.

Porous Media Flow Module Overview

Porous media exist in many natural and man-made systems, and the need for advanced porous media modeling spans many industries. Examples include processes in fuel cells, drying of pulp and paper, food production, filtration processes, and so on. The Porous Media Flow Module extends the COMSOL Multiphysics^® modeling environment to the quantitative investigation of mass, momentum, and energy transport in porous media. Its application areas range from conventional porous media flow, based on Darcy's law, to non-Darcian flow and multiphysics flow analysis, including the effects of heat transfer, chemical engineering, and more.

Contaminant concentration in ceramic water filter candles (left: undamaged, right: broken)

Porous Media Flow Module Functionality

Flow Models

The Porous Media Flow Module includes functionality for modeling single-phase flow in porous media based on Darcy's law, Brinkman's equations, and combinations of free and porous media flow. Fractures in porous media may dominate the flow and a specialized interface for fracture flow can be combined with any of the porous media flow models. Both stationary and time-dependent analysis types are available.

Multiphase Flow

The multiphase flow capabilities include transport of multiple immiscible phases through a porous medium, solving for averaged phase volume fractions. For variably saturated porous media, a nonlinear flow option, based on Richards' equation, can be used to analyze media where the hydraulic properties change as fluids move through the porous medium, filling some pores and draining others.

Multiphysics

The multiphysics capabilities include combinations with heat transfer, chemical engineering, and structural analysis. When combined with heat transfer, there are options for computing nonisothermal flows in porous media as well as effective thermal properties. Heat transfer in porous media can be combined with moisture transport for applications within consumer electronics, packaging materials, and building physics.

The module also treats the transport of chemical species in free flow, saturated, and partially saturated porous media. It can be used to study the flow and chemical composition of a gas or liquid moving through the interstices of a porous medium. Apart from porous media regions, the flow system may also include regions with free flow.

For elastic effects in a porous material, a specialized multiphysics interface for poroelasticity combines a transient formulation of Darcy's law with a quasistatic formulation of solid mechanics. The pore pressure from the Darcy's Law interface acts as a load for the structural analysis, thereby causing swelling or shrinking. Changes in volumetric strain affect the pore space, which acts as a mass source or sink for the Darcy's law flow model.

Thermal energy storage (TES) units are used to accumulate thermal energy from solar, geothermal, or waste heat sources. This example models the effects of heat transfer with phase change and local thermal nonequilibrium while charging the TES unit.

General Moisture Transport Interface Improvements

A new Concentrated species formulation is available in the Moisture Transport in Air interface to model convection and diffusion of vapor in air when the vapor content is high. This is often the case when there is moderate or high relative humidity at a high temperature. Under these conditions, the moist air density may vary significantly in space and time due to vapor concentration gradients, and the default formulation should be replaced by the new Concentrated species formulation.

The physics interface has also been improved to support supersaturation conditions that correspond to a relative humidity greater than one. This occurs when a hot stream saturated with water vapor is rapidly cooled down. Finally, the default solver settings for the various moisture transport, heat and moisture, and moisture flow interfaces have been set in a way that results in more robust and faster computation.

You can now select Concentrated species as the mixture type for moist air in the Moisture Transport interfaces.

New Tutorial Models

The Porous Media Flow Module includes several tutorial models.

Packed Bed Latent Heat Storage

Thermal energy storage (TES) units are used to accumulate thermal energy from solar, geothermal, or waste heat sources. The example models the effects of heat transfer with phase change and local thermal nonequilibrium while charging the TES unit.

Application Library Title:
packed_bed_latent_heat_storage

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Performance of a Porous Microchannel Heat Sink

Microchannel heat sink with porous substrate (brown) to enhance heat transfer coefficient. The plot for the figure of merit shows the best configuration.

Application Library Title:
performance_of_a_porous_microchannel_heat_sink

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Frozen Inclusion

Liquid water saturation after nine hours of progressive degradation of the initial frozen block due to heat conduction and convection in the surrounding porous medium. The isosurfaces show the temperature, and the remaining ice appears in white. The streamlines represent the fluid velocity field.

Application Library Title:
frozen_inclusion

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Wicking in a Paper Strip

Wicking occurs when a dry porous material is put into contact with a fluid; it will absorb the fluid due to capillary forces. The absorption continues until gravity balances the capillary force.

Application Library Title:
wicking_in_a_paper_strip

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