SimScale CAE Forum

FEA homework: Harmonic analysis of the fan


#1

FEA homework: Harmonic analysis of the fan

Tasks 1 and 2 involve performing a harmonic analysis on a fan which is modelled earlier. Click the following link to copy the project to your account.

Project Link : https://www.simscale.com/projects/demo2/fan_analysis_-_fea_harmonic/
Goto ‘Actions’ and ‘make a copy’.

You can also go to CAESES forum and obtain the geometry to modify it yourself:

Follow the steps below for setting up a harmonic analysis of the fan.

Task 1

The fan geometry is already present in the project. A mesh needs to be created for performing the analysis.

  • Click on the Baseline model and click Mesh geometry.

  • Select the options as shown below for the ‘Mesh operation’ - Tetrahedral automatic mesh and other properties (first order and moderate fineness). Click Save button and then Start the operation.

  • The mesh operation takes less than 5 minutes to complete. ‘Finished’ message is displayed across the operation once it is complete.

Task 2

The following task is to create harmonic simulation run for the above mesh. SimScale platform allows to select the ‘Analysis type’ from 5 different physical perspectives and a number of solver types are available to be selected within these broad classification, depending on the physics of the problem. The description of each physics and solver type are explained to help choose from the analysis types.

  • Select Simulation Designer tab and click on New simulation.

  • Solid mechanics - Harmonic analysis is selected as the Analysis type and Save button is clicked. This generates the entire simulation setup tree.

  • Click Domain from the sub-tree and select the mesh which was created. Click the Save button.

  • We need to create a point to get the result control (displacement magnitude). Select Geometry primitive and click Create new geometry primitive. Then select Point option.

  • Enter the coordinates as shown below and click on Save. The point is seen in the viewer.

  • Click on Materials from the sub-tree and click Add solid material

  • Scroll to the bottom and select Import from material library

  • Click on Steel and Save the material.

  • Change the damping properties as shown in the below figure, assign it to the mesh region and click on Save button.

  • Now select Constraint option under ‘Boundary conditions’ of the sub-tree and click Add constraint boundary condition.

  • Assign the face with specific boundary condition as shown below and click on Save.

  • Click on Load form the sub-tree and Add load boundary condition.

  • Enter the following values, assign the face with specific boundary condition as shown below and click on Save.

  • The numerics is changed as follows to select the type of solver for the harmonic analysis under consideration.

  • Click on Simulation Control along the sub-tree and enter the following values. Select the Save option.

  • Now we need to add some result controls to get data from the analysis. Click on Result control and select Add point data item.

  • Select the z displacement and magnitude and phase options to get the result controls at the point specified, which is the tip of a blade.

  • Click on Simulation runs and select Create new run. Enter the Start button.

  • Click on Post-Processor tab on the top of the screen. Click on the specific run and select ‘Point data’. The Displacement (magnitude) shows the z displacement of tip of the blade.

You can try some interesting similar analyses and post your results, along with a short explanation of what you tried to simulate!


#2

#3

#4

Hi Anna,

just want to let you know that I cannot access the fan via your project link.

Sorry, that content is not here or has been removed.

Please double check that your link is not mistyped and complete.

Cheers,

Jousef

Edit: Works now.


#5

Just analyzed the fan in a harmonic analysis as well as in a frequency analysis to see where my frequency bands are to run two simulations in the harmonic analysis part.

My results are below (please treat with caution :smiley:)

Frequency Analysis

Harmonic Analysis

Displacement from 1620-1650Hz

Displacement from 5440-5480Hz

Comparison of Displacements (Imaginary part as well as real part)

@1650Hz:

@5480Hz:


#6

Some fundamental questions for this type of analysis.

If I had NO damping I would not have an imaginary part meaning in my case that the excitation and response I get have a phase shift, correct?

Is there also a possibility to test the worst case scenario (resonant frequency) as @afischer mentioned in the webinar and estimate if our component will fail after a short/long period of time?

Thanks in advance :slight_smile:


#7

HI @jousefm,
if you had NO damping, there is no imaginary part and (equivalently) NO phase shift. Excitation and response are in the same phase.

Sure, as long as you have damping activated, you can run the harmonic analysis “exactly” on the resonant frequency and get the worst-case-response. Without damping, you would get a divergent solution, since the energy would approach infinity.

Features like fatigue analysis is currently not possible to be done on the platform, though we are working in it.
As fatigue is basically a post-processing step on top of a normal analysis, for simple cases I guess you could write a macro in paraview that you could run over the result of a harmonic/dynamic analysis from SimScale to get the fatigue estimation.

Best,
Richard


#8

Hi @rszoeke,

thanks for the detailed answer! :slight_smile:


#9

hi @rszoeke,
I think that actually when there is no damping then the solution is pure imaginary, while phase shift is irrespective of damping.