Tutorial: Incompressible turbulent airflow around a spoiler
In the following tutorial you find a step-by-step instruction to setup a Incompressible turbulent airflow simulation around a spoiler.
Import tutorial case into workbench
- To begin this tutorial, copy the original project.
- Once the ‘Work bench’ is open you will be in the ‘Geometries’ tab.
- Click on the CAD model named “Spoiler” to load the CAD model in the viewer.
- You can interact with the CAD model as in a normal desktop application
Create a New Simulation
- To create a new simulation click on the ‘+’ option next to ‘Simulations’
- Select ‘Incompressible’ and click ‘OK’
- After clicking ‘OK, a new tree will be automatically generated in the left panel with all the parameters and settings that are necessary to completely specify such an analysis
- All parts that are completed are highlighted with a green check. Parts that need to be specified have a red circle.
- The blue circle indicates an optional settings that does not need to be completed
- k-omega SST is used for turbulence modelling
- Choose Steady-State as we are not running a study that changes over time
Create a mesh
- Select the mesh option from the tree
- Set the mesh operation type to “Hex-dominant parametric (CFD only)”.
- Click on save (the blue tick button)
- Under the geometry primitives, we specify the Background Mesh Box dimensions by the values shown in figure below
- Next is the ‘Material Point’, that specifies the region to be meshed. Enter the parameters as shown and save.
- Next, we define additional primitives of type ‘Cartesian Box’ that will be used for mesh refinement later on
- Click on the ‘+’ option next to Geometry Primitives and select the Cartesian box from the drop down menu, as shown in figure
- Set the parameters as below and save
- Now we move on to the “Mesh Refinements”.
- To add a refinement click on the ‘+’ next to the Refinements and select the required refinement from the drop down menu
- To resolve all edges we add a Feature refinement that will refine the cells close to the edges of the spoiler
- Select the ‘Feature Refinement’ option from the ‘Refinements’ drop down menu
- Set the parameters as shown below, and save
- Add a refinement of type “surface refinement” to control the cell size on top of the wing surfaces
- Setup the values and properties as shown in figure below, and assign to the volume ‘solid_0’
- Add a new refinement of type ‘Region refinement’ and enter the values as shown and save
- Here, select the ‘Cartesian Box’, created earlier and click save
- Next we add a set of finer layer cells on the spoiler surface by selecting ‘Inflate boundary layer’ option from the ‘Refinements’ drop down list shown earlier
- Set the parameters as shown in figure below
- Select all the faces of the spoiler, and save
- Now, again click on the mesh option, set the bounding box resolution as shown below
- start the meshing operation
- After some time, the mesh will be finished and we can review it via the 3D viewer
- Next, add the materials from the ‘Material Library’ . First, we start with clicking on sub-tree “Materials”, click on ‘+’ from the options panel as shown.
- This pops-up a ‘Material Library’ from which we select “Air” and click on ‘Ok’. This will then load the standard properties for Air.
- Then, assign the material to the domain 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 initial conditions:
|velocity (x, y, z)
||(0, 0, 0)
Now, we come to define the boundary conditions.
- To create a boundary condition, click on the ‘+’ option next to the Boundary conditions and select the required boundary condition from drop down menu, as shown in figure.
- For the Inlet select the ‘Velocity Inlet’ boundary condition, specify the values shown in the figure below, assign inlet face for this boundary condition and click on save.
- For the outlet add a pressure outlet boundary condition and specify the settings as shown in figure below, assign the outlet face for this boundary condition and save it.
- For the Side and top sides, select the Slip type wall boundary condition as shown
- Define the bottom face as a ‘Moving Wall’, with wall velocity of 20m/s, as shown below
- Lastly, define the “Spoiler” faces as a ‘No-slip’ Wall
- The next item is Numerics. Here one can specify the numerical setup of the simulation.
- Use the settings as shown below
- 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.
Start a simulation run
- The last thing to do for running this simulation is to create a run.
- The new run is created by clicking on the ‘+’ symbol next to ‘Simulation Runs’
- Give a name to the run and start the run
- The convergence can be monitored simultaneously while the simulation is running by clicking on the ‘Convergence plots’ option under the Run
- The final convergence plot at the end of this simulation run is shown below
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)
Use the integrated post-processing system for result analysis as follows:
- Select the ‘Solution fields’ under the Run to post process the results
- Click the ‘+’ next to the ‘Cutting Planes’ to create a new cutting plane
- Set the scalar to ‘All velocit [node]’ to view the velocity distribution around the spoiler cross section