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Vawt , additional DOF for rotor blades
Dear all,
Regarding the turbine structural model, where can I find the structural properties (see picture) as f.e. the longitudinal, torsional, shear, … stiffness or the center of mass, elasticity, … for a NACA airfoil (more specific the NACA 0018)?
Kind regards,
Brecht Timmerman
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Dear all,
I find some information about it in documents below, but certainly not all of them …
- Effects of blade shape and its corresponding moment of inertia on self-starting and power extraction performance of the novel bowl-shaped floating straight-bladed vertical axis wind turbine – ScienceDirect
- (PDF) FREE VIBRATION ANALYSIS OF AN AIRCRAFT WING BY CONSIDERING AS A CANTILEVER BEAM (researchgate.net)
- Paper “Section Modulus and Bending Inertia of Wings”
Kind regards,
Brecht
Hi,
the structural properties depend on the cross sectional geometry (dimensions, shell thickness, internal beams, etc.) and the materials that are used.
In QBlade you can use QFEM, a very simplified model, to obtain such structural properties for simple cross sectional geometries and with isotropic material properties. More sophisticated designs must be done in a different FEA software – where some tools, such as BECAS from DTU are specifically made for wind turbine blade design.
BR,
David
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Dear David,
Oke thanks, but I think this is not possible for a vertical axis wind turbine mode. When I try it in the horizontal mode, I get an error because the rotor solidity is too large in my case (see figure Horizontal mode.png, H = 40 m, c = 2.5 m).
I then tried it for smaller values (H = 40 m, c = 1.5 m) and this was oke. However, when I performed the QFEM tool I don’t know where I can find the parameters lik longitudinal, torsional, shear, … stiffness or the center of mass, elasticity, … (see figure QFEM.png).
Can you help me?
Kind regards,
Brecht Timmerman
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Hi Brecht,
QFEM is not working for VAWT designs. However, since you are really only interested in the cross sectional properties you could simply recreate the blade geometry in the HAWT blade design and then do the QFEM analysis.
Since it doesnt really matter where your blade is located (this doiesnt change its structural properties) you could simply increase the “hub radius” to get around the issue with the solidity.
Once you have analyzed the blade structure you can eport it from the top menu via: “Blade Structure -> Export the current structural definition into QBLADE format“.
BR,
David
Oké, thanks Dr. David! I will try this out.
Dear Dr. David,
I tried it out and it worked to create a blade with structural properties.
I have however another question. To add these structural properties to your turbine design, I think it goes as follows. You upload the structural design file of the SANDIA 34m turbine available on QBlade (Structural design Sandia 34m.png) and make changes to this file. In particular, for the blade and strut design, I think you just have to change the name of the file by the blade you have just made (see Blades and struts SANDIA 34m.png). Is this correct? Next to this, I don’t know how to open these str. -files of the blade seperately so you can change some values manually? This should be possible if I check the documents available on Qblade (see Structural data table.png).
Kind regards,
Brecht
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Hi Brecht,
when you want to load a structural model all files (main file, blade files, struts files, etc.) need to be present in the folder from which you open the main file. When the main file is loaded then all other files that are specified in the main file are loaded successively. All of these files can of course be edited with a normal text editor. Also, then file ending can be arbitrary – so you could also just use the .txt ending for convenience. So if you want to change the structural blade file simply replace the “SANDIA34_Blade.str” file with your own blade table and update the filename in the main file accordingly.
BR,
David
Hi Dr. David,
It works for the blades and struts. However, I have some additional questions:
- How can I get the structural information about the tower and torque tube?
- Do you have the structural properties in the main file as well (see Structural data in main.png for the example of the SANDIA34m turbine available in as example)? If so, how do you get it in the main file?
- What do values you have to use for the Rayleigh dampening (RAYLEIGHDMP), stiffness tuner (STIFFTUNER), mass tuner (MASSTUNER) and DISC?
Kind regards,
Brecht
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Second bullet: Do you have to add the structural properties in the main file as well
