Replicating NREL-5MW in Actuator Disk Method

[KPerkins07]

Hello,

I am currently running simulations with Actuator disk method to replicate a NREL-5MW turbine but my confusion lies in how Incompact3Ds code is able to keep the power output below 5MW. I have run simulations with the size constraints of a 5MW turbine which can be seen below.

"CoR(x) CoR(y) CoR(z) YawAng[deg] TiltAng[deg] RotorDiam C_T[-] alpha[-]
630 90 315 12 0 126 0.8 0.17095
1512 90 315 0 0 126 0.8 0.17095"

However I am aware that I may be using too high of a C_T. Currently when running these simulations at the rated wind speed of 11.4m/s and including the use of a precursor simulation to include ABL flow I am still getting power outputs for turbine 1 as 5.8MW and in other simulations where turbine 1 has less yaw or where turbine 2 has more distance between it this increases even higher. I am unsure if it is specifically to do with the thrust coefficient that I am using but otherwise the simulation runs well I am just reaching power outputs that are not within the range.

Any guidance on where my issues may lie or ways in which to cap the maximum power output would be much appreciated.

Thank you in advance for any help.
If anymore information is needed please let me know.

[nbeb]

Hello,

The implemented actuator disk method computes the power as P=T*U (where P is the power, T the thrust, and U the mean wind speed through the rotor, see https://github.com/xcompact3d/Incompact3d/blob/master/src/adm.f90#L223). In other words, the code effectively assumes a power coefficient equal to the thrust coefficient. This is a deliberate modelling choice, as power estimates from the standard ADM are anyways not particularly accurate, and the relative performance between turbines in the farm remains unaffected. That said, you may multiply the results by the power coefficient post-simulation [also, based on the numbers provided, I would expect the power predicted by the ADM to be higher than 5.8MW].

Instead, for improved modelling which includes (i) NREL's ontroller and (ii) better calculations of power output we advise using the actuator line method (see the example in https://github.com/xcompact3d/Incompact3d/tree/master/examples/Wind-Turbine/NREL-5MW_ALM).

[KPerkins07]

Hello,

Thank you for your response. I had come to a similar conclusion when looking through the source code and appreciate you confirming this.
The resolutions that you have given are very helpful and much appreciated.

Regards,
Kiran