Tutorial: Incompressible turbulent airflow around a front wing
In this tutorial, aerodynamic analysis of a F1 frontwing is presented. The flow around the wing is modeled as an incompressible, turbulent flow using a k-omega SST turbulence model. This tutorial is based on the first part of the SimScale F1 Simulation workshop series about aerodynamics.
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 ‘Geometries’ tab.
Click on the CAD model named “FrontWing” to load the CAD model in the viewer.
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
Create a New Simulation
To create a new simulation click on the ‘+’ option next to the ‘Simulations’ tab
Select the ‘Incompressible Flow Analysis type 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. While, the blue circle indicates an optional settings that does not need to be filled out
k-omega SST is used for turbulence modelling
Since we are interested in a time invariant analysis the Steady-State option is activated
Create a mesh
To create a mesh, select the mesh option
Give an appropriate name to the mesh like ‘FrontWing mesh’
We set the mesh operation type to “Hex-dominant parametric (CFD only)”.
Adjust the Bounding Box Discretization to define the base size of the mesh.
We use the following values:
Bounding Box Discretization
Number of cells in x direction
Number of cells in y direction
Number of cells in z direction
You can also increase the number of processors used for the meshing process from 1 to 32 to reduce the time for meshing
Save the mesh operation by clicking on ‘tick’ symbol
Under the geometry primitives, we specify the Background Mesh Box dimensions by the values shown in figure below
Similalrly, change the “MaterialPoint” to (0, 1, 1)
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
We add a total of 3 cartesian boxes that will be used to further refine the mesh. This will increase the result quality of the simulation and allow enable you to resolve the wake of the wing.
The first one is called Region1 and has the following values:
The second one is called Region2 and has the following values:
The third one is called Region3 and has the following values:
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
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’
Next we add “region refinements” as follows.
The region refinements have levels 5, 6 and 7 to be very fine near the wing and coarse in the far field
Define region refinements with the refinement boxes you created earlier. The following values are used:
Similarly add level 6 for Region2 and level 7 for Region3 and save.
Next we add a set of finer layer cells on the wing 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 wing using the box select option, and save
Next, we add layer of cells at the bottom of the box, which will be the floor in the final simulation
Select the ‘Bounding Box Layer Addition’ from the refinements drop down menu
Set the Face to ‘Zmin’ to select the ground of the simulation
Set the remaining parameters as shown in figure
Lastly, to resolve all edges we add a Feature refinement that will refine the cells close to the edges of the wing
Select the ‘Feature Refinement’ option from the ‘Refinements’ drop down menu
Set the parameters as shown below, and save
Now our meshing operation is ready to go – let’s start it
After some time, the mesh will be finished and we can review it via the 3D viewer
Creating Topological Entity Sets
Now we will group the surfaces of the mesh into “Topological Entity Sets” which will help us to define the boundary conditions in the next step.
To create a topological entity set, first select the required face/faces
Then click on the ‘+’ next to the Topological Entity Set
Give the set an appropriate name and the click on the ‘Create new set’ button
This is illustrated for the ‘Inlet’ entity set below
Similarly, create entities for the remaining faces tabulated below
The table shows the set summary
bounding volume face1
bounding volume face2
bounding volume face3
bounding volume face4
bounding volume face0,bounding volume face5
All other surfaces
For the wing surfaces, instead of picking all the surfaces of the wing, you use the invert selection option
Figure shows all created sets
Creating and assigning 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.
Defining the Initial Conditions
Next item is Initial conditions. Here you can specify the state of the fluid at the beginning of the simulation. We are using the following:
velocity (x, y, z)
(60, 0, 0)
The next item is the Boundary conditions.
We use the topological entity sets created earlier to assign 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’ entity set for this boundary condition and click on save.
Next select a ‘pressure outlet’ boundary condition, set the parameters as shown below and assign this to the ‘Outlet’ entity set created earlier
Next select a ‘Symmetry’ boundary condition and assign this to the ‘Symmetry’ entity set created earlier
For the ‘Side-walls’, select the Slip type wall boundary condition as shown
For ‘Floor’, select the moving wall boundary condition
Lastly, for ‘Front Wing’, select the No-slip wall boundary condition
The next item is Numerics. Here one can specify the numerical setup of the simulation.
For this tutorial case, it is necessary to change some of the default settings.
Change Properties and ‘Relaxation factors’ according to the figure.
Additionally we will tweak some settings of the linear solvers according to the figure below:
Lastly change the following Divergence schemes.
Divergence scheme for div(phi,U)
bounded Gauss upwind
Divergence scheme for div(phi,k)
bounded Gauss upwind
Divergence scheme for div(phi,omega)
bounded Gauss upwind
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”
Specify the values as shown in figure below.
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
Once the simulation is finished, select the ‘Solution fields’ under the Run to post process the results on the platform. Or they can be downloaded and post-processed locally (e.g. with ParaView)
To view the streamlines through the front wing use the ‘Particle Tracer’ option
Set the parameters as shown in figures
Zoom in to visualize the flow over the front wing and shape of the wake formed
Figure below shows a post processing image form paraview
Last updated: April 10th, 2019
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