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

3.2 First Tower side-to-side

3.3  First drivetrain torsion

3.4 First Blade Collective Flap

3.5 First Blade Asymmetric Flapwise Pitch

3.6 First Blade Asymmetric Flapwise Yaw

3.7 First Blade Asymmetric Edgewise Pitch

3.8 First Blade Asymmetric Edgewise Yaw

3.9 Second Tower Fore-Aft

3.10 Second Tower Side-to-Side

3.11 Second Blade Collective Flap

3.12 Second Blade Asymmetric Flapwise Pitch

3.13 Second Blade Asymmetric Flapwise Yaw

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 AshesMode nameMode number in OC3 Phase I
11st Tower Side-to-Side2
21st Tower Fore-Aft1
31st Drivetrain torsion3
41st Blade Asymmetric Flapwise Yaw6
51st Blade Asymmetric Flapwise Pitch5
61st Blade Collective Flap4
71st Blade Asymmetric Edgewise Pitch7
81st Blade Asymmetric Edgewise Yaw8
92nd Blade Asymmetric Flapwise Yaw13
102nd Blade Asymmetric Flapwise Pitch12
112nd Blade Collective Flap11
122nd Tower Side-to-Side10
132nd Tower Fore-Aft9

A bar plot with the eigenfrequencies from the different participants in the OC3 Phase II project and from Ashes is available on the following link.


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:

https://www.simis.io/downloads/open/benchmarks/current/OC3_Phase_I_LC12 regression.pdf