## Is positive Yaw error clockwise?

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Alec.Mackendrick
Posts: 40
Joined: Thu Jun 28, 2012 10:37 am
Organization: Lloyd's Register
Location: UK

### Is positive Yaw error clockwise?

Hi

It seems like the industrial standard approach to yaw misalignment is that if the wind is approaching your turbine from a slightly clockwise direction (when viewed from above) to where your turbine is facing then you have a positive yaw error. To correct the error, you would yaw clockwise, in a positive direction.

Sadly this doesn't tie up with maths, which likes anti clockwise to be positive. I guess following the industrial standard, positive yaw moments would cause negative movements. I've had a quick rummage through the FAST manual, and it doesn't explicitly say which approach is followed (maths vs industrial standard).

Please could you let me know which way is positive when yawing and would you consider adding a top down view of a turbine to the manual in the section where the coordinate systems are described?

Thanks

Alec
Alec MacKendrick
Senior Control Specialist, EMEA
Lloyd's Register Group Limited

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

### Re: Is positive Yaw error clockwise?

Dear Alec,

In FAST, the wind direction output (HorWndDir), nacelle yaw angle input/ouput (NacYaw) and nacelle yaw error output (NacYawErr) are all defined counter-clockwise when looking from above (this is a positive rotation about the z-axis, which points vertically upwards). In AeroDyn, the wind direction input (WindDir) is defined clockwise when looking from above (which is opposite to that of FAST). For example, in Test01 from the FAST CertTest, NacYaw = -15 degrees and WindDir = -HorWindDir = 30 degrees, which equals NacYawErr = -15 degrees.

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

Alec.Mackendrick
Posts: 40
Joined: Thu Jun 28, 2012 10:37 am
Organization: Lloyd's Register
Location: UK

### Re: Is positive Yaw error clockwise?

Thanks Jason, yes it does.
Alec
Alec MacKendrick
Senior Control Specialist, EMEA
Lloyd's Register Group Limited

Julia.Hahn
Posts: 6
Joined: Wed Jun 10, 2015 12:59 am
Location: Germany

### Re: Is positive Yaw error clockwise?

Hi everyone,

I just want to make sure that I understood the explanation concerning FAST’s yaw convention right.
Would you be so kind to confirm that the picture I created is correct?
It’s supposed to show the turbine viewed from above. The black arrows point out the rotation direction of the blades.

Thanks – and kind regards,
Julia
Attachments
Yaw Direction.jpg (61.03 KiB) Viewed 5877 times

Jason.Jonkman
Posts: 5071
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Is positive Yaw error clockwise?

Dear Julia,

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

Julia.Hahn
Posts: 6
Joined: Wed Jun 10, 2015 12:59 am
Location: Germany

### Re: Is positive Yaw error clockwise?

Dear Jason,

thanks a lot for the quick response!

Best regards,
Julia

Mark.Capellaro
Posts: 12
Joined: Wed Aug 10, 2016 7:50 am
Organization: Disgruntled Goat GmbH
Location: Bavaria

### Re: Is positive Yaw error clockwise?

RE: FASTV8.16
Are any of the yaw options possible with the newest versions of FAST?
Mark C

Jason.Jonkman
Posts: 5071
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Is positive Yaw error clockwise?

Dear Mark,

What yaw options are you referring to?

Regardless, the yaw functionality is virtually unchanged between FAST v8.16 and earlier versions.

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

Mark.Capellaro
Posts: 12
Joined: Wed Aug 10, 2016 7:50 am
Organization: Disgruntled Goat GmbH
Location: Bavaria

### Re: Is positive Yaw error clockwise?

forgot to look under elastodyn inputs. thanks. M