Relative large power results of IEA 15MW with AeroDyn-OLAF method?

[ZL6462]

Dear all,

I am trying to simulate the IEA 15MW wind turbine at rated condition, namely 7.55 rpm at 10.59 m/s. however the power I got through AeroDyn-OLAF is about 17.5MW, which too larger compared with the rated15MW? Meanwhile, the result given by AeroDyn-BEM is about 15.8MW for the same condition, which is reasonable.

By the way, the simulation case is provided on "https://github.com/IEAWindTask37/IEA-15-240-RWT", and I simulated the turbine with the fixed-bottom. Besides, I have also modified some parameters of "OLAF.dat" as suggested by the Manual of OLAF.

Thank your for your attention. Best regards,

[jjonkman]

Dear @ZL6462,

Are you using the OLAF model of the IEA Wind 15-MW RWT found here, or something else: https://github.com/IEAWindTask37/IEA-15-240-RWT/tree/master/OpenFAST/IEA-15-240-RWT-OLAF?

Best regards,

[ZL6462]

Dear @jjonkman

Thank you for your quick reply, as you say, I got the model from "https://github.com/IEAWindTask37/IEA-15-240-RWT/tree/master/OpenFAST/IEA-15-240-RWT-OLAF".

And now, the minimum power I obtained is 16.8MW, and Cp is about 0.51, which is still larger than the rate value. And the simulation cost a longer time than the OLAF for NREL 5MW.

Best regards,

[ebranlard]

In a previous study, I had used the following parameters for OLAF (see the old input file here)

------------------- WAKE REGULARIZATIONS AND DIFFUSION -----------------------------------------
0       DiffusionMethod    Diffusion method to account for viscous effects {0: None, 1: Core Spreading, "default": 0}
3       RegDeterMethod     Method to determine the regularization parameters {0: Manual, 1: Optimized, 2: Chord, 3: Span, default: 0 }
3       RegFunction        Viscous diffusion function {0: None, 1: Rankine, 2: LambOseen, 3: Vatistas, 4: Denominator, "default": 3} (switch)
3       WakeRegMethod      Wake regularization method {1: Constant, 2: Stretching, 3: Age, default: 1} (switch)
0.5     WakeRegFactor      Wake regularization factor (m)
0.25    WingRegFactor      Wing regularization factor (m)
2000    CoreSpreadEddyVisc Eddy viscosity in core spreading methods, typical values 1-1000

This might slightly improve your results. Also, make sure to follow the guidelines so that your wake is long enough based on your time step and rpm (see guidelines). In general, we do observe higher Cp and Ct with OLAF, and so far we haven't fully dived into why.