# Design Help - NREL S818,S830,S831.

Good Day People,

First of all, let me thank Ms. Bonnie.Jonkman for giving me an access to the forum.

Coming straight to the point, I am working on my Master’s Thesis on design of wind turbine blades followed by FSI and optimization. My specifications are:

Power: 1MW
Airfoils: S818 (root)
S830 (Primary)
S831 (tip)
Rotor diameter: 55m
Tip speed velocity: 70.50 m/s
TSR: 8
Design wind speed: - 8.81 m/s
rpm: - 12.5 - 24.5

This data was based on the calculation. Now, I need assistance in:

1. How do I get/calculate the chord length and twist angle for each section of the blade. (Something like this http://www2.mae.ufl.edu/mdo/papers/5265.pdf on page 3)
2. At what sections or length should the airfoils transition take place i.e. from S818 - S830 - S831.
3. Any other data that I can be provided by NREL which can help me with my design and analysis.

Any other help is greatly appreciated,

Thank you,

Pranav Bhatnagar

Dear Pranav,

It sounds like what you want to do is an aerodynamic/performance optimization of a rotor based on a given set of airfoils. The HARP_Opt tool was developed for that purpose: nwtc.nrel.gov/HARP_Opt.

Best regards,

Respected Sir,

Thank you very much for your prompt response. I will surely work on it. If there is a doubt I shall revert you back.

Thanking you,

Sincerely,
Pranav Bhatnagar

Hello everyone,

I am designing a variable speed variable pitch wind turbine. As posted on the top are the specifications for the turbine. Later, I was advised to use HARP_Opt tool for optimization and calculation of the parameters related to the wind turbine.

I am writing the steps here that I am following, kindly let me know if I am going wrong.

Approach 1:

1. Use the values from -5 to 20 (from XFoil) and insert in the airfoilprep excel sheet and get data for -180 to +180 degrees.

2. Use this new data to create a airfoil database in the AeroDyn format. Do this for all 3 airfoils.

3. Use HARP_Opt and add all 3 files and let it merge together to get all the data.

Approach 2:

1. User the Airfoilprep excel sheet and blend all 3 airfoils together (1 - 2 - 3) and get the data for Cl and Cd

2. Use this data to make a new airfoil data in Aerodyn format and upload only 1 airfoil for HARP optimization.

One more question: How do I get the value for Aspect ratio and max CD for extrapolating values from -180 to +180. I did read the forum posts but didn’t get the proper idea of it.

PS: The AirfoilPrep_v2.02.02.xls Excel sheet that is uploaded in the website does not work. I tried to run it by disabling all security but in vain. I suggest you to kindly look into it.

Awaiting for the response.

Thanking you,

Sincerely,
Pranav Bhatnagar