OC3 Phase I load case 1.2
We have separated this load case from the rest of the OC3 Phase I benchmarks because this load case compares eigenfrequencies, which we compare differently than the load cases that compare time series.
1 Test description
In this load case, we compare the eigenfrequencies of the model between aeroelastic software. The results are given in figure 6 in Jonkman et al. (2010j).
2 Model
The model is the Offhsore NREL 5-MW reference wind turbine, which corresponds to the offshore template in Ashes.
3 Benchmarks
In the following sections, the different mode shapes are illustrated.
3.1 First Tower fore-aft
![](documents/appdocs/imgs/740e9364-6bb5-11eb-adb0-a434d9c3397a.png)
3.2 First Tower side-to-side
![](documents/appdocs/imgs/6006ce82-6bb5-11eb-a56d-a434d9c3397a.png)
3.3 First drivetrain torsion
![](documents/appdocs/imgs/81f096c8-ac6f-11ed-8fa2-586c25a85bc8.png)
3.4 First Blade Collective Flap
![](documents/appdocs/imgs/4bdc5f7a-6bb6-11eb-b085-a434d9c3397a.png)
3.5 First Blade Asymmetric Flapwise Pitch
![](documents/appdocs/imgs/3fead8b6-6bb6-11eb-8a2e-a434d9c3397a.png)
3.6 First Blade Asymmetric Flapwise Yaw
![](documents/appdocs/imgs/87d47650-6bb6-11eb-8de5-a434d9c3397a.png)
3.7 First Blade Asymmetric Edgewise Pitch
![](documents/appdocs/imgs/74a73fca-6bb6-11eb-ac16-a434d9c3397a.png)
3.8 First Blade Asymmetric Edgewise Yaw
![](documents/appdocs/imgs/87d47650-6bb6-11eb-8de5-a434d9c3397a.png)
3.9 Second Tower Fore-Aft
![](documents/appdocs/imgs/c800e0d2-6bb7-11eb-b891-a434d9c3397a.png)
3.10 Second Tower Side-to-Side
![](documents/appdocs/imgs/b5fe5c3e-6bb7-11eb-9e46-a434d9c3397a.png)
3.11 Second Blade Collective Flap
![](documents/appdocs/imgs/a61687a8-6bb7-11eb-a062-a434d9c3397a.png)
3.12 Second Blade Asymmetric Flapwise Pitch
![](documents/appdocs/imgs/97d4b750-6bb7-11eb-b993-a434d9c3397a.png)
3.13 Second Blade Asymmetric Flapwise Yaw
![](documents/appdocs/imgs/81ee6b3e-6bb7-11eb-bbbb-a434d9c3397a.png)
4 Results
The eigenfrequences of the model are solved and compared to those presented in the OC3 Phase I project. Note that the numbering of the eigenfrequencies in Ashes is from the lowest frequency to the highest, which is not the same as in the OC3 Phase I project. The table below summarises the numbering correspondance.
Mode number in Ashes | Mode name | Mode number in OC3 Phase I |
1 | 1st Tower Side-to-Side | 2 |
2 | 1st Tower Fore-Aft | 1 |
3 | 1st Drivetrain torsion | 3 |
4 | 1st Blade Asymmetric Flapwise Yaw | 6 |
5 | 1st Blade Asymmetric Flapwise Pitch | 5 |
6 | 1st Blade Collective Flap | 4 |
7 | 1st Blade Asymmetric Edgewise Pitch | 7 |
8 | 1st Blade Asymmetric Edgewise Yaw | 8 |
9 | 2nd Blade Asymmetric Flapwise Yaw | 13 |
10 | 2nd Blade Asymmetric Flapwise Pitch | 12 |
11 | 2nd Blade Collective Flap | 11 |
12 | 2nd Tower Side-to-Side | 10 |
13 | 2nd Tower Fore-Aft | 9 |
Note that only a visual check is performed in that report. Once we have a set of results that are in agreement with the other participants, we use that set as a base case to compare the results produced by Ashes daily. If these results differ from more than 0.01% with the base, a failed test notification is raise. The report can be found on the following link: