How to use Elastodyn to calculate tower loads at specific positions?

Wind & Water Computer-Aided Engineering Software Tools
1

Hello,

I am currently creating a model for a real onshore wind turbine that is equipped with strain gauges on certain sections of the tower. Now I am unsure how to define the parameters in ElastoDyn so that the simulation results are output at the height of the strain gauges in order to be able to later compare the measurement data with the simulation results.

I have the following tower proportions :

TowerBsHt = 0.87 [m]
TowerHt = 71.4 [m] (sum of the individual tower section lengths plus the tower base height)

The strain gauges are attached at the following heights (with regard to the base of the tower):

3.215m, 25.505m, 50.115m and 69.72m

In the documentation I found this formula for the definition of the parameter TwrGagNd in ElastoDyn:

Elev. of node J = TwrRBHt + ( J – 1⁄2 ) • [ ( TowerHt + TwrDraft – TwrRBHt ) / TwrNodes ]

Translated into the current parameter names and assuming TwrDraft = 0 the formula simplifies to

Elev. of node J = TowerBsHt + ( J – 1⁄2 ) • [ ( TowerHt – TowerBsHt ) / TwrNodes ]

If I understand correctly, I can now use the TwrNodes parameter (also defined in ElastoDyn) to control at which tower heights results can be calculated.

For TwrNodes = 45 I get the following elevations:

J = 2 → 3.22

J = 16 → 25.16

J = 32 → 50.24

J = 44 → 69.05

These elevations are close to the locations of the strain gauges. So, my input for ElastoDyn would be:

NTwGages = 4

TwrGagNd = 2,16,32,44

Are these assumptions correct, or have I misunderstood something?

Thank you in advance.

Best regards,
Sarah

2

Dear @Sarah.Lott,

Yes, I fully agree with your summary.

Just FYI: Normally TwrNodes is chosen based on convergence of the solution, rather than to align nodes to specific locations. And if the tower nodes are not exactly aligned with specific locations of interest, you could output loads at the two nodes that bound the location of interest, and interpolate between these data to get loads at the location of interest.

Best regards,