Power coefficient/Aerodynamic torque

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KumaraRaja.Eedara
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Re: Power coefficient/Aerodynamic torque

Postby KumaraRaja.Eedara » Tue Dec 10, 2019 11:16 am

Yes Jason. I am plotting AeroDyn output RtAeroCp.
Yes, Induced velocity calculation is disabled in my simulation. I did not think about the fact that Betz limit is valid only when BEMT is used.
Thanks for pointing that. Now I understand that exceeding Betz limit is sensible, but how is it possible to generate more power than that is available in the wind? Kindly advice me incase i'm missing something fundamental here. Thanks.

Regards,
Kumara

Jason.Jonkman
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Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Tue Dec 10, 2019 11:22 am

Dear Kumara,

Without induction, energy is not preserved in this simulation, so, energy-related quantities are not accurate. I would set WakeMod = 1.

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

KumaraRaja.Eedara
Posts: 52
Joined: Mon Sep 12, 2016 8:34 pm
Organization: IIT Bombay
Location: Mumbai

Re: Power coefficient/Aerodynamic torque

Postby KumaraRaja.Eedara » Tue Dec 10, 2019 11:35 am

Dear Jason,

Many thanks for your quick response. I'll do that.

Regards,
Kumara

KumaraRaja.Eedara
Posts: 52
Joined: Mon Sep 12, 2016 8:34 pm
Organization: IIT Bombay
Location: Mumbai

Re: Power coefficient/Aerodynamic torque

Postby KumaraRaja.Eedara » Thu Apr 22, 2021 2:26 pm

Dear all,

Issue: Difference in the aerodynamic power of rotor between Standalone AeroDyn calculation and OpenFAST calculation.

I have calculated Rotor aerodynamic power for WindPact 1.5MW turbine at (pitch=2.2 deg, rotor speed=24RPM, wind speed=12 m/s Uniform) using
1) Standalone version of AeroDyn15.04 and 2) OpenFAST-V2.40 but i see the difference in aerodynamic power of the rotor.

1) RtAeroPwr = 1954.472 kW
2) 'RtAeroPwr'= 2003.206 kW

In the OpenFAST simulation case some of the settings are GenDOF = 0, CompAero=2, shafttilt=0,precone=0.

I have made sure that the settings are same for both. What could be the reason for this discrepancy?
Also, does the Elastodyn play role in the calculation of the rotor aerodynamic power ("RtAeroPwr'") in OpenFast?

Regards,
Kumara

Jason.Jonkman
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Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Thu Apr 22, 2021 3:08 pm

Dear Kumara,

If all structural DOFs are disabled in ElastoDyn and if the geometry and wind are set up identically between the OpenFAST and standalone AeroDyn driver simulations, then I would expect the standalone AeroDyn driver to give the same aerodynamic power as OpenFAST. If the power predictions are different, I would expect that structural DOFs are enabled in ElastoDyn or some geometry or wind differs. Enabling structural DOFs in OpenFAST--e.g., blade deflection--can impact the aerodynamic power calculated by AeroDyn.

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

KumaraRaja.Eedara
Posts: 52
Joined: Mon Sep 12, 2016 8:34 pm
Organization: IIT Bombay
Location: Mumbai

Re: Power coefficient/Aerodynamic torque

Postby KumaraRaja.Eedara » Thu Apr 29, 2021 1:21 pm

Dear Jason,

I have made sure that all the parameters are the same between both AeroDyn (stand alone version) and AeroDyn in OpenFAST. But still I see significant difference between the Aerodynamic Power calculated using standalone Aerodyn vs OpenFAST.

Wind speed (m/s) Pitch (deg) Rotor speed (RPM) RtTSR RtArea (m^2) RtAeroPwr (W) RtAeroCp
12 5 15 4.5815 3848.4510 1420687.0 0.3488
12 5 15 4.5815 3848.4510 1417626.0 0.3480


Also, the AeroDyn input file of OpenFAST (V2.40) require some extra inputs like "AA_InputFile", "DBEMT_Mod","tau1_const", which are not present in the standalone AeroDyn input file. This may be because of the version difference. But I made sure that, the options I chose are agnostic to these differences, unless modifications are made to the way calculations are performed even with the same settings between the two (like "AFAeroMod"=1).

Currently I am using stand alone version of "AeroDyn_v15.04.02". If there is latest version, please let me know where to download it from.

I have attached relevant files. If it is not a big ask, could you please go through the attachment and and let me know if I am making any mistakes? Thanks.

Regards,
Kumara
Attachments
Test_AeroDYN.zip
(60.35 KiB) Downloaded 8 times

Jason.Jonkman
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Location: Boulder, CO
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Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Thu Apr 29, 2021 1:58 pm

Dear Kumara,

I did a quick comparison between your OpenFAST model and standalone AeroDyn model and don't see any obvious differences that would lead to different power.

I'm guessing the problem is that you are using two different versions of AeroDyn between the cases. You mention that you are using OpenFAST v2.4 and standalone AeroDyn v15.04. While we don't provide precompiled Windows executable of the standalone modules (like AeroDyn) with each OpenFAST release, the source code needed to compile the standalone AeroDyn driver is included in the OpenFAST v2.4 repository. The AeroDyn driver input file has not changed between AeroDyn v15.04 and OpenFAST v2.4. So, all you should have to do is compile the standalone AeroDyn driver for OpenFAST v2.4, use your AeroDyn driver file together with the AeroDyn input file(s) from your OpenFAST v2.4 model, and rerun the driver-level simulation.

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


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