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.
‘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
3D CAD model of the spoiler 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
Choosing an incompressible simulation from the Analysis window
k-omega SST is used for turbulence modelling Choose
Steady-State as we are not running a study that changes over time
Setting the turbulence model and steady state analysis type 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)
Options for setting up the mesh
Under the geometry primitives, we specify the Background Mesh Box dimensions by the values shown in figure below
Background Mesh Box
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
Creating a new geometry primitive
Set the parameters as below and save
Cartesian box parameters
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
Adding a mesh refinement
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
Inflate boundary layer
Now, again click on the mesh option, set the bounding box resolution as shown below
start the meshing operation
Start the meshing operation
After some time, the mesh will be finished and we can review it via the 3D viewer
Reviewing the generated Mesh Adding Materials
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.
Adding a new material
Assigning the material to the domain Initial Conditions
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.
Creating a new boundary condition
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.
Velocity Inlet boundary condition
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.
Pressure Outlet boundary condition
For the Side and top sides, select the Slip type wall boundary condition as shown
Wall Boundary condition
Define the bottom face as a ‘Moving Wall’, with wall velocity of 20m/s, as shown below
Moving Wall boundary condition
Lastly, define the “Spoiler” faces as a ‘No-slip’ Wall
No-slip wall boundary condition Numerics
The next item is
Numerics. Here one can specify the numerical setup of the simulation. Use the settings as shown below
Numerics-III Simulation Control
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.
Simulation Control 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
Creating a new simulation run Convergence Plot
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
Convergence Plot 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)
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
Velocity contour around the spoiler