How to define porosity in Ansys CFX ?

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 ANSYS CFX is another software for computational fluid dynamics (CFD) that can also simulate various phenomena involving fluid flow, heat transfer, and chemical reactions. Similar to ANSYS Fluent, ANSYS CFX can also model porous media, such as packed beds, filter papers, perforated plates, etc

To define porosity in ANSYS CFX, you need to specify a domain in which the porous media model is applied and the pressure loss in the flow is determined by your inputs. There are two approaches to set up the porous media model. 

In addition to the source term in the momentum equation, you also need to define the porosity value for the porous domain. The porosity is a dimensionless quantity that indicates the fraction of the domain volume that is occupied by fluid. The porosity affects the calculation of material properties, heat transfer, reaction source terms, and body forces in the porous medium. You can enter a constant value for the porosity or use a user-defined function (UDF) to specify a spatially varying porosity

To define porosity and resistance coefficients in ANSYS CFX using the graphical user interface (GUI), you can follow these steps:

  • Go to Domain panel and select the domain that you want to model as porous.
  • Enable Porous Media option and click Edit.
  • In the Porous Media panel, enter the value for porosity or select UDF option if you have a UDF for porosity.
  • Select either Standard or Power-Law option for Resistance Formulation.
  • Enter the values for resistance coefficients or select UDF option if you have a UDF for resistance coefficients.
  • Click OK to close the Porous Media panel and Apply to close the Domain panel.

To define porosity and resistance coefficients in ANSYS CFX using text commands (TCL), you can follow these steps:

  • Enable TCL mode by using the command: tcl
  • In TCL mode, type set domain-name [get "Domain:domain-name"] where domain-name is your domain name.
  • Type set domain-name.Porous Media = On to enable Porous Media option.
  • Type set domain-name.Porosity = value or set domain-name.Porosity = "UDF:udf-name" where value is your porosity value or udf-name is your UDF name for porosity.
  • Type set domain-name.Resistance Formulation = "Standard" or set domain-name.Resistance Formulation = "Power-Law" to select Resistance Formulation option.
  • Type set domain-name.Resistance Coefficients = "value1 value2" or set domain-name.Resistance Coefficients = "UDF:udf-name" where value1 and value2 are your resistance coefficients or udf-name is your UDF name for resistance coefficients.
  • Type end to exit from TCL mode.

For more information and examples on how to define porosity in ANSYS CFX, you can refer to these sources:

You can also watch this video that demonstrates how to simulate flow through porous media using ANSYS CFX:

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