NREL 5-MW reference turbine - CP, CQ, CT Coefficients

Dear Jason and Ranman,

I am using this data for my research and I was wondering if, since you posted it here more than a year ago, it has been published somewhere so that I can at least cite the source. If not, I guess I will just say that the data was obtained using WT_Perf.

Also I wanted to note that there seem to be some “wild points” scattered in the excel spreadsheets, some cells have a “-1000” value which looks like it does not belong.

Best regards,

Carlos Casanovas
MIT

Dear Carlos,

Speaking for NREL, we have not published these results.

Regarding the “wild points”, WT_Perf v3.00 would set ouput values to a large negative number (e.g., Cp = -9.9999) when it could not calculate a solution.

Best regards,

Dear Carolos,

It would be nice of you to provide me with your email, as I can’t find a way to answer your email sent through this forum.

Best regards
Rannam

Dear Rannam,

Do you have a script that runs through the various blade pitch angles?

Thanks,
Micky

Dear all,

thank you for your posts which helped me a lot to calculate the aerodynamic coefficients for different pitch angles. I used the FAST model input file which Rannam suggested on 15 March 2012.
Assuming wind speed to be constant (v_w =8m/s), a Tip Speed Ratio (TSR) of 5 to 10 (step 1) and Pitch angle -5.0 deg to 9.0 deg I run a simulation with FAST. As a result, I got pretty much the same results for power coefficient obtained by FAST as Rannam posted on 14 March 2012. Hence, I assume that there should not be anything wrong.

However, I faced a problem related to thrust coefficient cT. The problem came up doing a simulation with FAST for:
Pitch Angle: 0.0 deg
Wind Speed: 3.0 m/s to 25 m/s (step 1m/s)
Rotor Speed: 1.0 rpm to 15.0 rpm

You will find the results attached.

The problem is the following:

For the same TSR I should get the same thrust coefficients (as far as I understand the meaning of thrust coefficient right). But this is not the case.
For example: For a wind speed of 3.0 m/s and a rotor speed of 1 rpm TSR= 2.20. The resulting cT=1.515.
For a wind speed of 6.0 m/s and a rotor speed of 2 rpm TSR is also equal to 2.20. However, the resulting cT=0.492.

Does anyone of you know what could be wrong in this simulation? These results were generated with the same FAST input file as mentioned above. As the results of power and torque coefficient were quite reasonable, I wonder why thrust coefficient is so strongly deviating.

Sebastian Hippel
cT_P0deg.xls (49 KB)

Hello!

The mentioned problem could be solved by the hints given in the follwing forum topic: [url]http://forums.nrel.gov/t/the-effect-of-tilt-angle/769/1]

→ The sensor “RotThrust” is not the aerodynamic thrust as it includes gravity and inertial loads.

As a result, I was able to calculate the coefficients for a wide range of pitch angle and TSR

Best regards,

Sebastian

Dear All,

I am trying to implement the BEM method in MATLAB for wind turbine modelling. I have few questions, which are listed below.

First of all, I modelled the NREL 5MW offshore wind turbine in MATLAB. My algorithm is just like the Aerodyn, but with different high axial operation correction-Spera Corrections with ac=0.37-which corresponds to Wilson et Lissaman 1974. And to validate the BEM, i compared the Cp outputs with that of Wt_perf (the results that you post on Tue Mar 06, 2012 7:09 am).

`````` I set the initial conditions for induction factors to zero.
I set the Error tolerans to 0.005.
I added Prantl Tip and Hub Loss models.
I compared my results with that of WT_Perf
``````

1.My results seem almost fine when compared, but there is a little difference, especially in the high axial operation region, the turbulent state region, where Glauert correction is applied. And the difference is especially increasing at low velocities around cut-in velocity, high PRM. I am trying to get the almost the same result as WT_perf. As it is clear in figures, the results are almost same in the windmill state, the region where there is no correction. Do you have any idea for this difference? What may be the problem?

I attched my results. These results change according to the error tolerans value. But i could not get the results of the Wt_perfs in the high axial correction region.

By the way, my model output does not include the torque and thrust from the blade weight, pure aerodynamic torque and thrust. I don’t know Wt_Perf also gets torque, so power from the weight of the blades, either. From the results achieved and the results you put on the form, Wt_perf does not consider the weight effect because in low axial operation range, the results are same.

1. Apart from above, as unfortunately we know, there are more than one correction in the literature for high axial operation region. As I mentioned above, I utilized Spera’s with ac=0.37 corresponding to the one from the Wilson and Lissaman, which, I think, Wt_perf utilizes in older versions according to an article that I read. But I am not sure whether this is the same correction model for the Wt_perf 3.00?

From 1994 to 2012, There are many changes in Wt-perf. There is also a change that may be important for this difference written by Dr. Bulh as follows.

‘‘I replaced the equations to calculate the element Ct, Cp, and Cq with equations. Pat Moriarty gave me. It improved the correlation to the rotor Cp.’’ Please see these cahnges and the sentecence written by Dr. Bulh the link:HARP_Opt/ChangeLog.txt at master · NREL/HARP_Opt · GitHub

*I also realized that every correction formula, such as Glauerts or others, have square root term in their equation. During iteration, the term inside the square root gets negative value. Therefore, we get complex inflow angle, complex angle of attack, so Cl and Cd data from the corresponding angle of attack cannot be read. For interpolation in Matlab, i am using interp1 command, it says that it cannot work with complex number. But this problem, i think, is not the problem due to interp1. Therefore, i am putting a command like if the term inside sqaure root is less than 0 (negative), take the term very close to zero. With this way, i am a kind of changing the initial conditions. Is there any other mehtod that i can apply?

1. I also read about a paper about the iteration process of what Wt_perf used. Initially, as far as i am concerned, iteration for axial and angular factors were separately, that is the tangential induction iteration were nested inside the axial induction iteration in the previous version it says. In which version it is like this? My questions, WT_Perf V3.00 uses an iteration method just like Aerodyn? Which uses one iteration loop for both axial and tangential induction factors?

And lastly, what do you think about my results? Is it fine enough to move on simulink model etc to design controller after adding inertia, gear box ratio etc.?

Yours sincerely.

Mustafa SAHIN, PhD Candidate

METU Aerospace Engineering, Ankara, Turkey.

Dear Mustafa,

As discussed in the following topic on our forum, WT_Perf is no longer supported by NREL, but has been effectively replaced by the standalone driver for AeroDyn v15: http://forums.nrel.gov/t/wt-perf-being-removed-from-distribution/882/4.

As far as I can tell, your results are quite close to those of WT_Perf and because you are using a different high-induction correction; perhaps that explains some of the differences you are seeing. AeroDyn v15–and it sounds like your code–replace the subiterations for axial and tangential induction with a single iteration covering both; perhaps this explains some of the differences in the windmill state. Regardless, though, I would not be too considered with your BEM implementation. You could compare your results to those of AeroDyn v15 if you wanted another set of results.

WT_Perf, like the standalone driver for AeroDyn v15, does not include structural weight/inertia terms.

I can’t comment on specific releases of WT_Perf; you’d have to look at the source-code changes between releases to answer your related questions.

There should not be imaginary numbers resulting from the Glauert/Buhl correction, as the correction is not applied for cases beyond the bounds of the equation’s validity.

Best regards,

Dear Jonkman,

Again, thank you so much.

Yours sincerely

Mustafa SAHIN

Mr Jonkman,
I am running some incompressible CFD simulations of NREL 5MW reference turbine using Actuator Line method, solving RANS equations with k-epsilon model. Power and torque values I obtain for the same conditions are consistently a bit lower than results you present using FAST software. I know it can be related to my code, but I wonder does the FAST code model the blade to blade interaction, i.e. the flow is solved in the rotational plane (in the angular direction), or does it use a simpler method like Blade Element Momentum Theory?
Regards,
Hüseyin

Dear Hüseyin,

Yes, the AeroDyn aerodynamics module of FAST uses the Blade Element/Momentum Theory.

Best regards,

Hi all,

I am looking to obtain CP(TSR, Beta) and CT (TSR, Beta) surfaces for the 5MW reference offshore wind turbine in a similar way as Jason and Rannam did with WT_perf back in 2012 but for a wider range of TRS and pitch values. From what I’ve read through different threads of the forum WT_perf is no longer distributed, but I still should be able to do a similar analysis using Aerodyn V15 standalone driver somehow. I would like to obtain an output with a similar format to that attached by Jason in his post from Mar 06, 2012. Problem is I am new to the use of FAST and Aerodyn and I don’t quite know how to configure the input file to establish the desired value ranges, or even if that is possible.
Does someone have and example input template for that or can help me in any way?

Rocío

Dear Rocio,

The standalone AeroDyn driver input file can be set up to run multiple cases for different wind speeds (WndSpeed), rotor speeds (RotSpd), and pitch angles (Pitch) via the “Combined-Case Analysis” options. You can include the rotor aerodynamic power and torque in the AeroDyn output file by including “RtAeroCp” and “RtAeroCt” in the output list (OutList) in the AeroDyn primary input file. Simply run multiple cases and take the time- (or, preferably, azimuth-) averaged torque to find the RtAeroCp and RtAeroCt as a function of WndSpeed, RotSpd, and Pitch (or RtTSR).

Best regards,

Dear Jason,

Doing as you say, I would have to define a row for each simulation, fully specifying all of the wind speed, rotor speed and pitch values. And I get I would be obtaining an output file corresponding to each of these rows (containing the time-series information for each chosen output sensor), which given the number of simulations I would have to run to cover the value ranges I want, would be tough to post-process. I wonder if there is a way to run a parametric analysis, giving in the input file the direct ranges (e.g Pitch from -5 to 5 deg with a delta increment value of 1 deg → -5.0, 5.0,1.0 ) and obtain a single output file where I could find the tables with Cp/Ct values for each pair of wind speed and rotor speed, 1 table per pitch (Just the same as the output file that was obtained with WT_perf and that you posted on the 6th of March of 2012). If there is not, I will have to do as you propose.

Best regards,

Rocío

Dear Rocio,

No, the standalone AeroDyn driver is not set up to run a parametric analysis that generates one output file for multiple cases. I would think a simple script could be written to do this, but I don’t have one I can send you. The key is that the output from standalone AeroDyn for each case is a time series–and what you want is the mean of this time series (or preferably the azimuth average), resulting in one value of RtAeroCp and RtAeroCt for each case. If you have MATLAB, the MCrunch post-processor could be used to calculate these mean values, or you could write your own script to do that.

Best regards,

Dear Jason,

Ok, I understand that, thank you very much for your help.

Best regards,
Rocío

Hello again,
I’ve been working on NREL-5MW wind turbine and there is something bugging me. This turbine is rated at wind speed = 11.4m/s and TSR = 7 (as stated here: nrel.gov/docs/fy09osti/38060.pdf) for 5MW of power. Examining the document and assuming this is an offshore wind turbine, considering the air density as 1.225 kg/m^3, Cp at design conditions is 0.44. When I observe in Mr. Jonkman and Mr. Chaaban’s results, higher Cp is achieved at even lower wind speeds. I am also getting higher values using RANS-ALM methodology. Now I might be wrong but AeroDyn and FAST are used to obtain results in that document. I am not sure what I’m missing in the consistency here. I am also having a hard time finding reliable experimental or numerical results on this turbine in journals or papers.
Some data I have found:
iopscience.iop.org/article/10.10 … 082003/pdf
brage.bibsys.no/xmlui/bitstream … sAllowed=y (this paper also refers to this forum)
Other sources you might come across would be extremely valuable, as well as your ideas on the matter I’ve mentioned.
Best regards,
Hüseyin

Dear Hüseyin,

I’m not sure I understand your concern, but I would expect a maximum aerodynamic Cp of the NREL 5-MW wind turbine to be around 0.48 in region 2 using blade-element/momentum (BEM) theory. Of course, some power is lost in the mechanical-to-electrical conversion (generator efficiency), so, the effective electrical Cp would be less.

Best regards,

Dear Jason,

I computed the thrust coefficient vs wind speed with the stand alone Aerodyn V15.
The results are shown below.
Does the results seem coherent?

Thank you.

Best regards,
Etienne JARGOT

Dear Etienne,

Yes, your results look like what I would expect for the NREL 5-MW turbine.

Best regards,