What is a Porous Medium?
A porous medium is a substance that contains pores or spaces between solid materials through which liquid or gas can pass. Examples of naturally occurring porous media include sand, soil, and some types of stone, such as pumice and sandstone. Sponges, ceramics, and reticulated foam are also manufactured for use as porous media. The possible applications of these materials in science, industry, and everyday life are vast, although they are perhaps most commonly used as filters. Physically, a porous medium can be distinguished from other materials — including other porous media — by its porosity or the size of its pores. Materials with low porosity are less permeable and typically have smaller pores, making it more difficult for gas or liquid to pass through them, while materials with high porosity have large pores and are easily permeated. Porosity is an important consideration in filtering since if particles must be removed by a porous medium, the pores must be small enough to trap them effectively. Geologists also consider the porosity of the surrounding stone and soil when conducting observations of oil and natural gas reservoirs. Natural gas trapped in low-porosity stone is known as “tight gas” and is more difficult to access than other reserves.
Porosity ranges from a low percentage in dense shale and sandstone to about 50% in the sand and up to 70% in clay. Artificial materials can be even more porous. For example, reticulated foam, a porous medium used in air conditioner filters and cosmetic applicators, has a porosity of up to 98%.
CFD Simulations inside a Porous Medium in ANSYS Fluent Software
The porous media model can be used for a wide variety of single-phase and multiphase problems, including flow through packed beds, filter papers, perforated plates, flow distributors, and tube banks. When you use this model, you define a cell zone in which the porous media model is applied, and the pressure loss in the flow is determined. Heat transfer through the medium can also be represented, subject to the assumption of thermal equilibrium between the medium and the fluid flow.
The porous media models for single-phase flows and multiphase flows use the Superficial Velocity Porous Formulation as the default. ANSYS Fluent calculates the superficial phase or mixture velocities based on the volumetric flow rate in a porous region. However, it is important to note the following for multiphase flow:
- In the Eulerian multiphase model (this section in the separate Theory Guide), the general porous media modeling approach, physical laws, and equations described below are applied to the corresponding phase for mass continuity, momentum, energy, and all the other scalar equations.
- The Superficial Velocity Porous Formulation generally gives good representations of the bulk pressure loss through a porous region. However, since the superficial velocity values within a porous region remain the same as those outside the porous region, it cannot predict the velocity increase in porous zones, thus limiting the model’s accuracy.
Porous media are modeled by adding a momentum source term to the standard fluid flow equations. The source term comprises two parts: a viscous loss term (Darcy) and an inertial loss term.
Where is the source term for the ith (x, y, or z) momentum equation, is the magnitude of the velocity, and D and C are prescribed matrices. This momentum sink contributes to the pressure gradient in the porous cell, creating a pressure drop proportional to the fluid velocity (or velocity squared) in the cell.
To expand your knowledge about this model and its application in the industry and academic fields, and also how to use it inside the Ansys Fluent software, you can enter the Porous tab by clicking on the link to find more projects, for instance, using this method, the following simulation models a Porous Mixer for Increasing the Heat Transfer of Nanofluid.
MR-CFD, an Expert in the Field of Porous Medium Simulations
With several years of experience in simulating various problems in various CFD fields using ANSYS Fluent software, the MR-CFD team is ready to offer extensive modeling, meshing, and simulation services. Simulation Services for acoustical simulations are categorized as follows:
- Premixed Combustion in Porous Zone
- Capillary Action (wicking), Water flows in porous media
- Multiphase Flow in Porous Medium, Filter Cake Formation
- Water infiltration into a porous concrete block
- Porous Mixer for Increasing the Heat Transfer of Nanofluid
- Non-Equilibrium Heat transfer in Porous Aluminum Foam Heat Sink
You may find the related products in the categories mentioned above in our CFD shop by clicking on the following link:
Our services are not limited to the mentioned subjects, and the MR-CFD team is ready to undertake different and challenging projects in the CFD simulation of porous medium fields ordered by our customers. You can consult with our experts freely and without charge and order your project by sending the details of the problem to us using the following address.
By outsourcing your project to the MR-CFD as a CFD simulation freelancer, you will not only receive the related project’s files (Geometry, Mesh, …), but also you will be provided with an extensive tutorial video demonstrating how you can create the geometry, mesh, and define the needed settings(pre-processing, processing and post-processing) in the ANSYS Fluent software all by yourself. Additionally, post-technical support is available to clarify issues and ambiguities.