## How the effective wind speed is calculated?

Discuss the effects of turbulence on wind turbines and its simulation.

Moderator: Bonnie.Jonkman

Robert.Unguran
Posts: 12
Joined: Mon Mar 10, 2014 10:04 am
Organization: forwind
Location: Germany

### How the effective wind speed is calculated?

Dear all,

I am trying to understand the basic of the effective wind speed calculation therefore I would like to know whether my step by step approach is correct:
1 - Reading out the u,v,w component of the turbulent wind field from a file (u_v_w)
2 - Introducing scaling plus wind shear u_v_w =(Mean_Wind_speed + u_v_w .* [scale_u scale_v scale_w])*wind_shear
3 - Propagate the wind field with the mean wind speed along the u axes.
4 - At the rotor plane include the rotation correction with respect of the of the yaw, tilt, and roll u_v_w = R_w*R_v*R_u *u_v_w
5 - Adding the tower fore-aft velocity and the blade velocity to the u component

Is the final u component used to calculate the angle of attack and effective wind speed?

Regards,
Robert

Jason.Jonkman
Posts: 5771
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: How the effective wind speed is calculated?

Dear Robert,

I'm assuming this question pertains to AeroDyn/InflowWind in the latest release of FAST (v8.12)?

Steps 1-3 are discussed in the InflowWind User's Guide: https://wind.nrel.gov/nwtc/docs/InflowWind_Manual.pdf (but the details depend on the wind-file type).

How AeroDyn v15 makes use of the wind, together with the structural velocities, in steps 4-5 is discussed in the draft AeroDyn User's Guide and Theory Manual: https://wind.nrel.gov/nwtc/docs/AeroDyn_Manual.pdf. Basically, for the blade-analysis nodes, AeroDyn v15 uses the relative velocity between the wind and structure at each node, expressed in a local coordinate system, in the induction calculation (to find the inflow velocity and angle of attack). This relative velocity is also effected by the influence of the tower on the wind (tower dam or tower shadow, depending on what's enabled). AeroDyn v14 treats all these calculations a bit differently, as outlined in Appendix G of the manual.

I hope that helps.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Robert.Unguran
Posts: 12
Joined: Mon Mar 10, 2014 10:04 am
Organization: forwind
Location: Germany

### Re: How the effective wind speed is calculated?

Dear Jason,

Thank you for the help.

Regards,
Robert