Incompressible turbulent airflow around a spoiler


The content of this tutorial is not up to date with the current live version of SimScale. The tutorial setup and the results are still valid! Please do not get confused if styles like buttons and entity names have changed in the meantime.

In the following tutorial you find a step-by-step instruction to setup a Incompressible turbulent airflow simulation around a spoiler.

Tutorial Link:

Import tutorial case into workspace


1) Import tutorial project

  • To start this tutorial, you have to import the tutorial project into your ‘Dashboard’ via the link above.
  • Once the ‘Work bench’ is open you will be in the ‘Mesh creator’ tab.
  • The Mesh Creator tab is the place where you can upload CAD models and create meshes for them.
  • The geometry is already available under the ‘geometry’ tree item.
  • Click on the CAD model named “spoiler” to load the CAD model in the viewer.
  • After a few moments, the CAD model is displayed in the viewer like shown in the figure below
  • You can interact with the CAD model as in a normal desktop application

The CAD model displayed in the viewer

2) Create a mesh

  • To mesh the geometry, click on geometry in the Navigator tree and click on the blue Mesh geometry button in the settings panel.
  • In this tutorial we choose the “Hex-dominant parametric (CFD only)”, so rename the mesh operation accordingly and press enter to save.

Adding a mesh operation (Hex-dominant parametric) within the Mesh Creator

  • After saving new tree entries will be generated that will be used to setup the meshing parameters.
  • We start with the ‘BaseMeshBox’ and enter the parameters as shown and save.

Define the base mesh box for the Hex-dominant parametric operation

  • Next is the ‘Material Point’, that specifies the region to be meshed. Enter the parameters as shown and save.

Define the Material Point for the Hex-dominant parametric operation

  • Next we define additional primitives of type ‘Cartesian Box’ that will later be used for mesh refinement. Enter the parameters as shown and save.

Define an additional box for the inner mesh refinement zone

  • Now we move on to specify the ‘Mesh refinements’.
  • So click on ‘Mesh Refinements’ from the tree and ‘Add mesh refinement’ button from the settings panel.
  • Select the ‘Type’ as ‘feature refinement’ and enter the values as shown and save

Add an feature refinement to refine the edges of the spoiler

  • Add a new refinement of ‘Type’ as ‘Surface refinement’ and enter the values as shown and save
  • Here, click on ‘selection’ on the toolbar on top of the viewer and click ‘select all’ to select all faces.
  • now click ‘Add selection from viewer’ to assign surfaces for refinement and save.
  • Add a new refinement of ‘Type’ as ‘Region refinement’ and enter the values as shown and save
  • Here, select the ‘Cartesian Box’ from the window and click save at the bottom.

Define a region refinement with the refinement box

  • Lastly, add a new refinement of ‘Type’ as ‘Layer refinement’ and enter the values as shown and save
  • Again select all faces and assign. ( as was done for surface refinement)

Add a refinement of the boundary layer near the spoiler

  • Now click on the ‘Hex-dominant parametric (only CFD)’ in the tree and enter the main settings as shown and click save at the bottom.
  • Then click ‘start’ at the top to begin the meshing process.

Main settings for Hex-dominant parametric mesh


A mesh clip through the spoiler for mesh reviewing purposes

3) Specify the simulation properties

Having created the mesh, we can move on to the Simulation Designer tab in which we can create the actual numerical simulation setup. The images below show you the setup step by step.

  • So , click ‘New simulation’ and give a name.
  • First, we choose the analysis type. First switch to the Fluid Dynamics section of the analysis types
  • Here we will use the Incompressible analysis type, with the options steady-state and a k-omega-SST turbulence model (in the properties of the analysis type)
  • As soon as we save the analysis type choice, the tree is automatically expanded with all the parameters and settings that are necessary to completely specify such an analysis.
  • Therefore you can simply go through the tree to complete the setup
  • All parts that are completed are highlighted with a green check. Parts that do need specification have a red circle

Simulation type choice

  • Next item is Domain. Choose here the mesh that we just created (via its name)

Assign the mesh to this simulation

  • Next item is Materials. Here you select the material properties of the fluid material.
  • Click ‘Add material’ and then click ‘Import from material library’ button at the bottom.
  • Select ‘Air’ and click save.
  • Now assign this material to the domain volume by selecting it from the ‘Topological mapping’ selection window and save.
  • Next item is Initial conditions. Here you can specify the state of the fluid at the beginning of the simulation. Specify the following:
Variable Value Unit
pressure 0 m^2/s^2
velocity (x, y, z) (0, 0, 0) m/s
k 0.24 m^2/s^2
omega 1.78 1/s
  • The next item Boundary conditions. Click ‘Add boundary condition’ and follow the figures as shown.
  • Define the “Inlet” as shown below ,assign the corresponsing face and save.
  • Define the “Outlet” as shown below ,assign the corresponsing face and save.
  • Define the “Side-top” as shown below ,assign the corresponsing faces and save.
  • Define the “Bottom” as shown below ,assign the corresponsing face and save.
  • Lastly, define the “Spoiler” as shown below ,assign the corresponsing face and save.
  • The next item is Numerics. Here one can specify the numerical setup of the simulation.
  • Select the solver as shown below and keep the default values.
  • Under Simulation control we can specify the global parameters of the simulation run
  • Since we are running a steady-state analysis, the time steps are only “quasi time steps”
  • So setup the parameters as shown.

Set up the simulation control parameters such as run time and time step length

4) Start a simulation run

  • The last thing to do for running this simulation is to create a run for it. This means that we take a snapshot of the simulation setup that can not be changed anymore afterwards. This allows us at a later point to always review what kind of setup this simulation run had
  • Click on Create new run
  • The new run is created and you can review all setting by expanding it
  • Then, hit the Start button and confirm
  • We can always see the current status of the run via the progress bar

Create a new simulation run and start it


Review of the convergence plot

5) Post-Processing

Once the run is finished, the results can be viewed in the Post-processor.

  • The results can now either be post-processed in the integrated post-processing environment (currently in beta)
  • Or they can be downloaded and post-processed locally (e.g. with ParaView)
  • Follow the figure below to goto the last result step.

Use the integrated post-processing system for result analysis

  • Create a clip to view the results.