Tutorial: Frequency Analysis of an Airfoil (1/2)

This is a tutorial about how to set up a frequency analysis of an airfoil and how to visualize the results. Note that this is the first tutorial of a series: In this tutorial, we are analyzing the eigenfrequencies which are the basis for the harmonic analysis done in the second tutorial, Harmonic Analysis of an Airfoil.

displacement airfoil results — Figure 1: Visualization of the displacement on the airfoil.

This tutorial teaches how to:

Set up and run a frequency analysis.
Assign boundary conditions, material and other properties to the simulation.
Mesh with the SimScale standard meshing algorithm.

You will be following the typical SimScale workflow:

Preparing the CAD model for the simulation.
Setting up the simulation.
Creating the mesh.
Run the simulation and analyze the results.

1. Prepare the CAD Model and Select the Analysis Type

Note

All solid geometry should be free of any interference, intersecting surfaces, and small edges. Issues such as these should be fixed in CAD before bringing the geometry into the SimScale platform. More specific preparation details are mentioned here.

Before starting to set up the model, check the following:

Please make sure that the imported geometry consists of solid parts and not sheet/surface elements.
If the geometry has many small fillets or round faces that are insignificant for the analysis, then it is recommended to de-feature and remove this geometry in CAD. This will dramatically reduce mesh cell count and therefore solve time.

First of all click the button below. It will copy the tutorial project containing the geometry into your own workbench.

Import Tutorial into Workbench

The following picture demonstrates what should be visible after importing the tutorial project.

cad model airfoil tutorial starting point — Figure 2: Imported CAD model of the airfoil in the SimScale workbench.

Did you know?

This is a simple airfoil geometry. This type of geometry is used for different applications, including automobile aerodynamics and fans. Completing a frequency analysis will show where the airfoil is likely to break due to the natural frequencies within the body.

1.1. Create the Frequency Analysis Simulation

Once the geometry is in the platform, click on it, and then choose the ‘Create Simulation’ option:

create new simulation blade — Figure 3: Creating a new simulation.

Then select the ‘Frequency Analysis’ type.

analysis type frequency airfoil — Figure 4: Selecting the frequency analysis simulation type.

2. Set Up the Simulation

2.1. Materials

The SimScale platform comes with a large number of default materials. In order to add a new one, click on the ‘+’ next to the Materials tab.

add new material simulation tree — Figure 5: Adding a new material.

A solid material is fitting for this kind of frequency analysis. Select the ‘Aluminium‘ from the Material list that will appear and hit ‘Apply’.

material list aluminium — Figure 6: Selecting aluminum for the blade material.

The blade will be assigned automatically. Leave the material properties at their default state.

properties material assignment material blade — Figure 7: Aluminium properties and assignment.

2.2. Boundary Conditions for the Frequency Analysis

Apply fixed support to the side face of the airfoil. Start by clicking on the ‘+’ icon next to the Boundary Conditions, and then picking the ‘Fixed Support’ option from the menu. This way, the assigned face will be fully constrained.

boundary conditions fixed support add new — Figure 8: Adding a fixed support boundary condition.

Apply a fixed support to the side face of the airfoil.

face assignment airfoil fixed support — Figure 9: Assigning the fixed support on the edge of the airfoil.

2.3. Simulation Control & Frequency Analysis Numerics

The default values for the Numerics are fine for this simulation.
Within simulation control, the eigenfrequency scope must be set to first modes, with the number of modes being equal to \(10\), as its default value.

simualtion scope eigenfrequency scope — Figure 10: The simulation control panel.

3. Mesh

The standard mesher will be used. For this tutorial, keep all settings as default and hit ‘Generate’. For linear FEA simulations, SimScale will create a 2nd order mesh by default, which aims for more precision in FEA studies (definition under the Element technology tab).

standard algorithm mesh settings — Figure 11: The standard algorithm meshing settings.

Did you know?

Often, increasing the global mesh refinement may cause a large rise in the cell/node count. This happens because the entire domain is getting refined.

When using the standard mesher, you can apply refinements only to regions of interest by using local element size and region refinements.

The resulting mesh will look like this:

second order mesh for a frequency analysis — Figure 12: The generated second order mesh.

4. Start the Simulation

In order to create a new run, click on the ‘+’ next to the Simulation Runs:

new simulation run simulation tree — Figure 13: Simulation setup tree before starting the simulation.

Now you can start the simulation. While the results are being calculated you can already have a look at the intermediate results in the post-processor. They are being updated in real-time!

5. Post-Processing

After about 18 minutes you can have a look at the results.

5.1 Eigenmodes & Eigenfrequencies

When expanding the information of the finished run, there is a Statistical Data section under the Plots, that includes the calculated eigenfrequencies. You can view the data, or even download them by clicking on the icon at the top of the table as highlighted below:

eigenmodes and eigenfrequencies table under the plots statistical data results of frequency analysis — Figure 14: Inspect or download the resulting data of the simulation by clicking on the icon highlighted by the arrow.

5.2 Surface Visualization

In order to view the results of your frequency analysis, click on the ‘Post-process results‘ tab under your finished run.

post-processing the results after the run is finished — Figure 15: After the simulation is finished, you can check the results in the post-processor.

Choose the “Displacement Magnitude” to display on your part as Coloring. In order to improve the quality of your visualization, and make the color transition smoother, right-click on the legend bar at the bottom, and select the ‘Use continuous scale‘ option:

choosing continuous scale and displacement magnitude in post processing — Figure 16: Choose the ‘**Use continuous scale**‘ option, for smoother transition between different levels of displacement.

You can visualize more parameters by changing the Coloring input.

5.3 Displacement

There are more features to use in order to post-process the results of the run, and you can access them by clicking on the ‘Add filter’ option. Then the menu with all the available options appears:

post processing filters for results visualization — Figure 17: All the available filters are listed on this menu, including the displacement. Choose the one you want to use, and a panel with settings will appear.

Select ‘Displacement‘ from the menu. You will notice that there is no difference after you create this new filter, so apply the following settings:

Set the Scaling factor to ‘0.25’. This will only change the physical deformation of the model, and for this simulation, the scale was brought down to 0.25 because it makes the natural frequencies easier to identify.
Rollback to the previous written timestep, which represents the 9th eigenfrequency shown in Figure 14. Each step is a different frequency, and you can display whichever you wish.

displacement field visualization — Figure 18: Toggling the displacement field with a scaling factor of 0.25, so the results are enhanced.

With a frequency analysis, one can determine the natural frequencies for a geometry. This information is valuable and can be used to get more meaningful results in the harmonic analysis that comes in the next step. Make sure to check the Harmonic Analysis of an Airfoil to learn more!

Analyze your results with the SimScale post-processor. Have a look at our post-processing guide to learn how to use the post-processor.

Congratulations! You finished the tutorial!

Have a look at the finished project