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Issues Importing Beam Cross Sectional Data for VAWT

Hello QBlade Community,

I am attempting to build an aeroelastic model of a H-Darrieus type turbine. I created the structural files in HAWT mode since QFEM is not available for VAWTs, but the geometric and structural properties should be the same. Following the Sandia example project, I created a main structural file to define each structure of the turbine but it outputs the following errors when I try to save the turbine:

Structural Model File:

‘hdarrieus_main.str

Structural Model: Problem assigning Beam Cross Sectional Data!

Structural Model Construction failed. Check the debug output…

I am currently unsure of where the error stems from but the files are attached here for your convenience for you to investigate. I defined the model to have a hub of size 0, I don’t know if this is what is causing the issue. This is how the tower and torque tube are defined:

——————————- TOWER AND TORQUE TUBE ———————
1 TWRHEIGHT – Height of the (fixed – non rotating) tower [m]
hdarrieus_tower.str TWRFILE – Name of file containing properties for the tower

1 TRQTBHEIGHT – Height (or length) of the torque tube (the rotating part of the tower) [m]
hdarrieus_trqtube.str TRQTBFILE – Name of file containing properties for the torque tube

1 TRQTBCLEAR – Clearance of the torque tube, must be <= TWRHEIGHT [m]
1 HUBPOS – height position of the generator hub that is connecting the torque tube with the fixed tower (VAWT only) [m]
1 TRQTBCONN – Absolute height position, starting after torque tube clearance, of a frictionless bearing that connects the torque tube to the fixed tower [m]

1 RTRCLEAR – Rotor clearance
0.5 BLDCONN – Absolute height position, starting after rotor clearance, of blade of the rigid blade torque tube connection 1 in [m] (VAWT only)
1 BLDCONN – Absolute height position, starting after rotor clearance, of blade of the rigid blade torque tube connection 2 in [m] (VAWT only)

If anyone can have a look at my files and explain where and why these errors are emerging I would greatly appreciate it!

Best regards,

Daniel Roman

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Hi Daniel,

the issue is that you have NAN values in your structural data tables, otherwise the model seems fine.

One suggestion: You are using the BLDCONN keyword. This keyword is used to fix the rotorblades “rigidly” to the torquetube at the assigned position. Since your rotor includes struts, the struts already connect the blades and torquetube explicitly, you dont really need this “extra” connection. The BLDCONN features intention is rather to fix the blades of “eggbeater” shaped VAWT’s directly to the torquetube, when they are in close proximity.

BR,

David

Hello David,

Thank you for your response and the suggestion. I looked at the structural data tables on a Linux machine but I didn’t see any NAN values. Could you give an example of where these NAN values are? Is there a way in QFEM to create structural data tables without NAN values that can work for VAWTs? Or should I just make a script that can change these NAN values to zero?

Thanks again,

Daniel Roman

Hi Daniel,

if you check the contents of “hdarrieus_trqtube.str” for instance, in the first row of your RGX_[-] column, the entry is NAN.

I dont know how it got there, but simply replace it with a non NAN value. If you remove the NAN values from all tables the structural model will build just fine.

BR,

David