Fluid Volume Extraction

A fluid mechanics simulation requires the air/fluid volume. For internal fluid flow analyses, this region needs to be created as a single part.
This can be done on the SimScale platform and is called Fluid Volume Extraction. There are three methods available:

  1. Open Inner Region
  2. Closed Inner Region
  3. Enclosure

Open Inner Region

This operation generates a fluid volume for an open inner region. The extraction is performed by:

  1. Selecting the boundary faces that lie between the external environment and the internal (highlighted in blue)
  2. Selecting one internal seed face (pink)
  3. Running the extraction
Flow volume partially created
Flow Volume being created within an exhaust silencer
extracted fluid volume
Successfully created fluid volume

By default, the solids are removed when the fluid is created. It is possible to keep them by enabling the ‘Keep Existing Parts’ toggle.

toggle option
Keep existing parts option (highlighted in Red)

Fluid volume with existing solid parts

Fluid volume with existing solid parts

Closed Inner Region

This feature enables the creation of fluid regions within closed volumes. The operation here is similar to the case above, except only one internal seed face is required. An example of the operation performed on a theater CAD model is shown below.

theater model 1
Selecting an internal seed face for a theater model
Resulting fluid volume


This option is generally used for external flow problems. The operation is performed by sizing the enclosure and then running the extraction operation. The example below shows a half symmetry air domain being created for a race car CAD geometry.

Half symmetry domain created
Creating an External Fluid Domain
Resulting External Fluid Domain

A demo of the above cases can be found in the link below: