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Tutorial: Post-Processing Fluid Flow Simulations

Post-Processing is the process of extracting the required information from the results generated by the simulation.

When a successful simulation is finished, the run dialog box will prompt the user with a “Post-process results” button. Clicking this button or selecting “Solution Fields” in the Simulation tree will open the result files in the online post-processor.

Accessing the post-processing environment in SimScale
Click the ‘Post-process results‘ button to open the simulation result data in the online post-processor.

Loading the result data in the post-processor can take up to a couple of minutes, depending on the result data size.

Post Processor Tools

SimScale post-processor functions and filters
Post-Processor interface map. Read below for a description of the functionality each component contains.

Frame Selection Tool Box

The Frame selection Tool Box is used to navigate through the time steps of the result data. In case of a successful steady-state simulation case you’ll usually want to investigate only the last time step (converged field data).

View Tool Box

The View Tool Box can be used to visualize the model in different view modes – Surface, Transparent Surface, Surface Mesh, Lines, Points, etc. For example, using the Surface Mesh view mode, you can visualize the mesh as shown below:

Changing surface visualization in SimScale post-processor
The view tool box allows to change the render mode of the model.

Selection Tool Box

The Selection Tool Box allows to set the rotation point, inspect specific result nodes and define the selection behavior in the viewer.

Filters Panel

The Filters panel contains all the visualization tools we require to post-process the results.

A list of parts present in the geometry can be found within the “Parts” section in the Filters panel.

Note: When there are multiple parts (solids) in your CAD model, they can be hidden from view by clicking the hide button (eye) next to the part names.

A list of available visualization tools is given below:

  • Cutting planes (slices)
  • IsoSurfaces
  • IsoVolumes
  • Animations
  • Particle Traces
  • Screenshots

Cutting Planes

Cutting Planes or Slices are used to visualize the results on a particular cross-sectional area.

Steps to create a Cutting Plane:

  1. Select the “+” button near the Cutting Planes filter.
  2. Under the Filters panel, now you can see the settings for the cutting plane. Here you can set the normal axis for the cutting plane.
  3. Using the sliding bar, you can set the position of the cutting plane along the selected axis.
  4. The Scalar option allows to select a specific result field to be visualized on the cutting plane.
  5. The Vector option allows the user to set the vectors (usually velocity vectors) on the plane.
  6. Opacity can be used to set the visibility of the plane.
  7. Options “Show Element Mesh” and “Clip model” can be used to visualize the Mesh elements and the geometry along with the cutting plane.
Post-processor cutting plane on SimScale
Cutting Plane settings within the SimScale online post-processor.

Iso Surfaces

The Isosurface filter can be used to isolate regions in the model which match a given variable value. For example, if the user wants to know where the pressure is exactly 10 [Pa], a cutting plane can be used to visualize those areas.

Steps to create an Isosurface:

  1. Create a new Isosurface from the Filters panel using the “+” button.
  2. In the settings below, you can select the flow variable to be visualized, set the Iso value (value to be plotted) and the Opacity level.
  3. In the example below, we have the settings to display the regions with 10 [Pa] pressure.
Isosurface filter on SimScale's post-processor
Isosurface filter settings.


Similar to the Isosurface filter, the Isovolume filter can be used to isolate volume regions in the model which match a given variable range.

Steps to create Isovolumes:

  1. Create a new Isovolume from the Filters panel using the “+” button.
  2. In the settings below, the user can select the flow variable to be visualized and set the iso value range as well as the Opacity level.
  3. In the example below, we have the settings to display the regions with pressure in the range of 10 [Pa] to 100 [Pa].
Isovolume settings on SimScale's post-processing environment
Isovolume filter settings

Particle Traces

Steps to create Stream Lines/ Particle traces

  1. Create a new Particle Trace¬†from the Filters panel using the “+” button.
  2. Then in the Filter settings panel, you can see the settings for the Particle traces. Please select the “SEEDS” tab.
  3. At the bottom of the settings panel, Select the Pick option and click on the model to set the source point for the stream lines. (As an example, you can pick the inlet faces to see the behavior of the flow starting at the inlet).
  4. It’s also possible to increase the density of stream lines and the spacing between stream lines using the settings.
SimScale particle traces filter
Filter settings for particle traces. Remember to select the “Pick” button in the Seeds tab to define the origin of the traces.


Steps to create Screenshots

  1. Place the model in the required position.
  2. Create a new Screenshot¬†from the Filters panel using the “+” button.
  3. You can define a custom name for the Screenshot by double clicking the screenshot name.
  4. To download the Screenshot, use the download button at the bottom of the filter settings panel.
Taking screenshots in SimScale's post-processing environment
Screenshot controls within the SimScale online post-processor.

Last updated: July 30th, 2020

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