load and response output of tower

[QB-Lin]

I am using 15 MW HAWT. I hope to get the wind load (TwN1Fdx, ...TwN9Fdx) and structural response (TwHt1MLxt, ..., TwHt9MLxt) of tower. I have some questions about the node index of tower.

1. Tower node in elastodyn

In the ElastoDyn.dat file of OpenFAST, the TwrNodes is generally set as 20.
'''
20 TwrNodes - Number of tower nodes used for analysis (-)
'''
However, in the ElastoDyn_Tower.dat, THE DISTRIBUTED TOWER PROPERTIES only have 10 rows.

'''
---------------------- DISTRIBUTED TOWER PROPERTIES ----------------------------
10 NTwInpSt
...
...
HtFract TMassDen TwFAStif TwSSStif
(-) (kg/m) (Nm^2) (Nm^2)
0.000000000000000e+00 2.300642131074250e+04 6.770513741893661e+12 6.770513741893661e+12
1.114034260838268e-01 2.038926791017103e+04 6.012509438660999e+12 6.012509438660999e+12
2.228068521676536e-01 1.774601273898164e+04 5.243768263364071e+12 5.243768263364071e+12
3.342102782514804e-01 1.506280308193614e+04 4.460141520157670e+12 4.460141520157670e+12
4.456137043353072e-01 1.234240777801470e+04 3.662296012994249e+12 3.662296012994249e+12
5.570171304191340e-01 9.633099266285813e+03 2.864340844739592e+12 2.864340844739592e+12
6.684205565029608e-01 7.026968999232271e+03 2.093608918221600e+12 2.093608918221600e+12
7.798239825867876e-01 4.645483574127345e+03 1.386599057692824e+12 1.386599057692824e+12
8.912274086706145e-01 2.596093483450980e+03 7.761060822822759e+11 7.761060822822759e+11
1.000000000000000e+00 1.715031343116859e+03 3.489844253733395e+11 3.489844253733395e+11

'''
In the elastodyn, is the tower uniformly divided into 19 parts from bottom to top based on DISTRIBUTED TOWER PROPERTIES, and then generate 20 nodes?
The TwrGagNd in elastodyn increases from the tower bottom to top?
If I set NTwGages as 9, and set TwrGagNd as "2, 4, 6, 8, 10, 12, 14, 16, 18", can I get the global response of tower from bottom to top?

2. Tower node in aerodyn

Similarly, in aerodyn15.dat, NumTwrNds=11, and 11 tower section characteristics are defined.
'''
====== Tower Influence and Aerodynamic
TwrShadow/=0, TwrAero=True, or Buoyancy=True]
11 NumTwrNds -
TwrElev TwrDiam TwrCd TwrTI TwrCb !TwrTI used only with TwrShadow=2, TwrCb used only with Buoyancy=True
(m) (m) (-) (-) (-)
15. 10. 0.5 0.1 0.0
28. 10. 0.5 0.1 0.0
41. 10. 0.5 0.1 0.0
54. 10. 0.5 0.1 0.0
67. 10. 0.5 0.1 0.0
80. 10. 0.5 0.1 0.0
93. 10. 0.5 0.1 0.0
106. 10. 0.5 0.1 0.0
119. 10. 0.5 0.1 0.0
132. 10. 0.5 0.1 0.0
144.386 6.5 0.5 0.1 0.0
'''
However, the maximum NTwOuts is 9, indicating that all the wind load on the 11 points could not be shown.
Is the tower uniformly divided into (NumTwrNds-1) parts and generate NumTwrNds nodes?
The TwrGagNd in aerodyn increases from the tower bottom to top?
1, 3, 5, 6, 7, 8, 9, 10, 11 TwOutNd
If I set NTwOuts as 9, and set TwOutNd as "1, 3, 5, 6, 7, 8, 9, 10, 11", can I get the global wind load on tower from bottom to top?

[jjonkman]

Dear @QB-Lin,

Here are my responses to your questions:

1. The tower in ElastoDyn is split into TwrNodes equally spaced elements with analysis nodes located at the centers of the these elements. The data in the distributed tower data at the NTwrInpSt stations is interpolated to the analysis nodes. The nodes are numbered from the bottom to the top, with node 1 being at the center of the first element, but if you have more than 9 TwrNodes, you can't output data at all of them (loads at the tower-base and tower-top can be output separately from ElastoDyn, but not based on node number).
2. The aerodynamic analysis nodes in AeroDyn are specified directly and need not be equally spaced. The nodes are numbered from the bottom to the top, but if you have more than 9 NumTwrNds, you can't output data at all of them.

I hope that helps.

Best regards,