# Blade nodes in BeamDy and ElastoDyn

Hi,

can someone tell me, where the nodes (BldGagNd or OutNd) are located? When i set the number of nodes to 3, does that mean that i have following locations:
node 1 is located at the blade root
node 2 is located at the blade mid
node 3 is locared at the blade tip

I hope someone can help me.

Best regards
Kemal

Dear Kemal,

OutNd in BeamDyn is documented in the BeamDyn documentation on OpenFAST readthedocs–see: openfast.readthedocs.io/en/mast … input-file.

Here is how BldGagNd is defined in ElastoDyn:
When CompAero=1 (using AeroDyn v14), the structural nodes in ElastoDyn are identical to the aerodynamic nodes in AeroDyn, so, BldGagNd corresponds to a row in the radially distributed data (radius RNodes) in the AeroDyn v14 input file.
When CompAero=2 (using AeroDyn v15), the blade is split into BldNodes equally spaced elements and the nodes are located in the centers of those elements, so, the first node is at 1/2*(TipRad-HubRad)/BldNodes from the root, the second node is at 3/2*(TipRad-HubRad)/BldNodes from the root, etc.

I hope that helps.

Best regards,

Thank you very much! This helped me.

Best regards
Kemal

Hi,

is it right when I have a blade with a length of 54m and BldGagNd is 9 that the nodes are on following points:

1 3
2 9
3 15
4 21
5 27
6 33
7 39
8 45
9 51

Best regards
Kemal

Dear Kemal,

In ElastoDyn, the structural blade analysis nodes are located at the centers of the structural elements. If you are using AeroDyn v14, the blade nodes/elements are specified in the AeroDyn v14 input file (and the structural nodes/elements are one-to-one with the aerodynamic nodes/elements). If you are using AeroDyn v15, the structural and aerodynamic discretizations differ, and structurally, the blade is split into BldNodes equally-spaced elements, so, node 1 is at a radius of (TipRad-HubRad)/BldNodes*(1/2), node 2 is at a radius of (TipRad-HubRad)/BldNodes*(3/2), etc. BldGagNd is a simply a list of (up to 9) nodes from the BldNodes total analysis nodes that can be used for output, e.g., if NBlGages = 2 and BldGagNd = 5,7, then output node 1 is structural node 5 and output node 2 is structural node 7.

Best regards,

Hi,

I have an additionol question to be sure i understand it correct. In the ElastoDyn summary file are the interpolated blade properties.
In my case I set in ELastoDyn the teo parameters like this:

```100 BldNodes - Number of blade nodes (per blade) used for analysis (-) 6, 15, 34, 43, 52, 62, 71, 82, 95 BldGagNd - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0]```
I want the blade loads at the following blade positions (from hub center) ``` 2.970 m, 7.830m, 18.090m, 22.950m, 27.810m, 33.210m, 38.070m, 44.010m, 51.030m ```
These are the summary outputs.

```Node BlFract RNodes (-) (-) (m) 6 0.055 2.97 15 0.145 7.83 34 0.335 18.09 43 0.425 22.95 52 0.515 27.81 62 0.615 33.21 71 0.705 38.07 82 0.815 44.01 95 0.945 51.03 ```

Is my input in ELastoDyn correct?

Best regards
Kemal

Dear Kemal,

Yes, your input looks correct. The value of RNodes in the ElastoDyn summary is the distance along the pitch axis from the hub center to each blade analysis node, and you’ve identified the correct nodes in the BldGagNd list.

Best regards,