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Trouble Obtaining/Exporting Structural Simulation Outputs for VAWT

#1 · 3. February 2023, 07:55

Hello,

I am a university student working on a VAWT project. I am somewhat stumped in my efforts to try and obtain structural simulation output data for a VAWT simulation (Just to be clear, I am checking the box that says “save structural data”). Unfortunately, reading through the forums and documentation has not helped my case. I have listed my questions below:

1.) Other than QFEM being an exclusive tool for HAWT, can users obtain all the same raw data outputs for VAWTS simulations that they are able to for HAWT simulations, even if it cannot be visualized in Qblade specifically?

2.) If VAWT simulations are able to get the structural data, where can users dig this output data out from? Exporting any of the example turbine simulation outputs has not been much help in my search.

3.) If the answer to question 1 is no, then does anyone know of any other software that can be used to simulate a VAWT and export said structural data?

4.) This question has to do with what I see when I open the ‘.sel’ exported simulation results file. Every variable seems to have a ‘scale factor’. I was wondering what the ‘scale factor referred to.

Thank you in advance for taking the time to read this message. 🙂

Brian has reacted to this post.

#2 · 4. February 2023, 18:26

Quote from David on 4. February 2023, 18:26
Hello Ryan,
in the structural simulation part in QBlade the turbine is modeled with beam elements. Since beam elements dont explicitly resolve the three dimensional blade or tower structure these beam elements need to have cross sectional structural properties assigned, this is similar to how lift and drag coefficients are assigned to a blade station when modeling aerodynamics.
These cross sectional properties can be generated for example with QFEM, although QFEM is a very simplified approximation of a structural blade design and assumes isotropic material properties. Since wind turbine blades are complicated composite structures many specialized software tools (such as BECAS tool from DTU) are available that can be used to design a blade structural layout and obtain the cross sectional beam properties (link to examplary blade and tower properties). In this sense QFEM could be seen as a very simplified version of BECAS.
However, QFEM is not a tool to perform time domain simulation of the wind turbine, QFEM only generated structural properties and modeshapes / frequencies. When using QFEM it doesnt really matter if you use the generated structural properties for a HAWT or VAWT blade, for instance you could generate the blade structure for a simple straight blade in QFEM and use these properties in an aeroelastic VAWT simulation.
After you have obtained structural properties, with QFEM or with another software, you can use them to setup a wind turbine structural model. More info on this is shown in the documentation here: Turbine Structural Model. When you have generated a turbine design with a structural model you can use this turbine in a time domain simulation and also output all kinds of data, such as forces, moments, velocties, acceleration etc. at any part of the turbine. As an example for the structural model of a VAWT you can checkout the SANDIA 34m template that you find in the Model Files section on the downloads page. When you export the turbine design of the SANDIA 34m into the .trb file format (Turbine Definition ASCII File documentation), you can checkout the generated files in the /Structure folder – these contain the structural turbine definition.
Regarding the .sel files. This is a HAWC2 data format which is described in the HAWC2 Manual and is compatible with the amazing Pdap post-processing tool from DTU. But you can also export data into more human readable ASCII formats from the export dialog.
I hope this helps a bit…
Cheers,
David

Hello Ryan,

in the structural simulation part in QBlade the turbine is modeled with beam elements. Since beam elements dont explicitly resolve the three dimensional blade or tower structure these beam elements need to have cross sectional structural properties assigned, this is similar to how lift and drag coefficients are assigned to a blade station when modeling aerodynamics.

These cross sectional properties can be generated for example with QFEM, although QFEM is a very simplified approximation of a structural blade design and assumes isotropic material properties. Since wind turbine blades are complicated composite structures many specialized software tools (such as BECAS tool from DTU) are available that can be used to design a blade structural layout and obtain the cross sectional beam properties (link to examplary blade and tower properties). In this sense QFEM could be seen as a very simplified version of BECAS.

However, QFEM is not a tool to perform time domain simulation of the wind turbine, QFEM only generated structural properties and modeshapes / frequencies. When using QFEM it doesnt really matter if you use the generated structural properties for a HAWT or VAWT blade, for instance you could generate the blade structure for a simple straight blade in QFEM and use these properties in an aeroelastic VAWT simulation.

After you have obtained structural properties, with QFEM or with another software, you can use them to setup a wind turbine structural model. More info on this is shown in the documentation here: Turbine Structural Model. When you have generated a turbine design with a structural model you can use this turbine in a time domain simulation and also output all kinds of data, such as forces, moments, velocties, acceleration etc. at any part of the turbine. As an example for the structural model of a VAWT you can checkout the SANDIA 34m template that you find in the Model Files section on the downloads page. When you export the turbine design of the SANDIA 34m into the .trb file format (Turbine Definition ASCII File documentation), you can checkout the generated files in the /Structure folder – these contain the structural turbine definition.

Regarding the .sel files. This is a HAWC2 data format which is described in the HAWC2 Manual and is compatible with the amazing Pdap post-processing tool from DTU. But you can also export data into more human readable ASCII formats from the export dialog.

I hope this helps a bit…

Cheers,

David

Brian and Ryan_Z have reacted to this post.

#3 · 5. February 2023, 03:20

Thank you for the reply. It was very helpful. However, I do have some follow up questions:

1.) For the exported files, I am still a bit confused on what the “Scaling Factor” is. Would you be willing to elaborate?

2.) Correct me if I am wrong, but from my understanding of your reply, Qblade is best used to obtain these values, along with other data, but the data should be input into a dedicated structural solver if we want to see stresses and displacements correct?

3.) I used what you recommended and was able to plot the force and moment outputs along the height of the blade, so thank you. However, I was unable to bulk export the numeric values of the graphs at all. I am specifically interested in exporting the data from the tangential force vs blade height graph for a range of pre-specified time steps. Could you inform me on how to go about doing this?

4.) Do you know of any software that I can use to calculate the blade displacement and stresses, given the force, moment, etc. values that I export from Qblade?

Thank you again for your help.

Brian has reacted to this post.

#4 · 5. February 2023, 16:50

Hi Ryan,

regarding your question:

The .sel format is defined in the HAWC2 manual and the scaling factors should be described there.
QBlade gives you displacements (a beam can be displaced) but no stresses (as the beam is only 1D and doesnt model the cross sectional area). You can get stresses either from a software or calculate it yourself analytically using the moments from QB and the second moment of area of the cross section.
If you export the complete simulation data through the menu: Turbine Simulation -> Export Data, the complete data that was recorded during the simulation is exported in bulk. This also contains the complete tangential forces at every blade station for each timestep of the simulation
Any software that allows you to create FEA models of the blade can be used, such as ANSYS, COMSOL, Solid Works but there is also a lot of specialized software BECAS, VABS and many more…

Best,

David

Ryan_Z has reacted to this post.

#5 · 12. March 2023, 12:28

Hello there,

As a question to the fourth question of the last message, can you directly import the blades/rotor/turbine made in QBlade into the ANSYS /Solid Works (or even ABAQUS) software? Or do you have to make it separately in f.e. Solid Works and then import it into those FEA packages?

Kind regards,

Brecht

#6 · 13. March 2023, 21:05

Hi,

there is the feature to export a blade geometry into the STL or into a .tst point cloud format. This export however only generated the outer shell of the blade and no internals. In other words you would need to construct a blade model in ANSYS or ABAQUS more or less from scratch.

BR,

David