Using multiple airfoil tables with ReNum as parameter

Wind & Water Computer-Aided Engineering Software Tools
1

Hi all,

I am trying to set up a simulation with multiple airfoil tables in FAST/AeroDyn. I am planning to use the Reynolds number ReNum as criterion. Unfortunately I do not know how to implement it properly. The User’s Guides are very short on this topic and I also found no helpful hints on this Forum or the internet.

Is ist right that I have to make changes to the Aerodyn input file (an additional line with ReNum??? in the last line) aswell as
I have to apply 2 changes to the airfoiltables I want to use with multiple entries (Number of airfoil tables in this file and Table ID parameter ??)
Are there any restrictions for the multiple airfoil table (same length??)

Unfortunately it is not working for me. Can you please help me with this issue.
Best would be an example input document you used for your computations, so I could see where I have to apply the changes.
Or a little description where I have to manipulate the input documents to get it running.

Thank you very much,

Andreas

2

Hi Andreas,

I just started working with FAST myself and not too long ago I was trying to accomplish the same thing that you were. What has worked for me is:

  1. Renum as the last line of the .ipt file
  2. Changing the Airfoil table (see attached example). I have not included all values for brevity.Example_Airfoil_data.txt (2.39 KB)
    You can also refer to the test aerodata files included in the FAST archive - CertTest\AeroData\SWRT
  3. I have had to use same length/AOA values for all Re numbers to get it to work. I am not sure if FAST or rather Aerodyn allows use of multiple length files. Hopefully someone with a little bit more experience can address this issue.

Good Luck.

Regards,

Subin.

3

Hi Subin,

Thanks very much. It works totally different from what I tried to do.
Do you know if it is possible to do the same without cm values, using NO_CM.
Unfortunately the method we use to get our cl and cd values do not yield cm. Otherwise I would add one line with only zeros.

Where did you get your information from how to implement multiple airfoils in FAST. I couldn’t find anything.

Andreas

4

Hi Andreas,

You are welcome. I believe you can exclude the Cm values as long as you are using the No_Cm option. I got the information from the AeroDyn user’s guide, since from what I understood, the airfoil data is actually used by Aerodyn to calculate the aerodynamic loads. Its not a very detailed guide but it gets you started and I also looked at the test cases included included in the FAST archive and played around with the options till FAST was happy. You can also look at the Aerodyn Theory manual if you want to get a better idea of how it works. If you dont mind me asking, how are you obtaining your airfoil data, are you using experimental data or are you calculating it theoretically?

Subin.

5

Hi Subin

no problem. We are using the airfoildata for the NREL 5MW Turbine. You can download them. What we are trying to do is to apply a passive control concept to the NACA 643618 airfoils (flexible trailing edge). For these we are obtaining our airfoildata from theory.

Andreas

6

Dear Andreas and Subin,

Thanks, Subin, for answering Andreas’ question.

The ReNum option is explained on page 13 of the AeroDyn User’s Guide. Also, Section 9 explains how to create airfoil data files with muiltiple airfoil tables.

With regards to the pitching moment coefficient, Subin is correct that the value is not need in the multiple-Reynold’s-number airfoil data file if the NO_CM option in AeroDyn is set. In fact, this is how tests 15-17 in the FAST CertTest are made.

Best regards,

7

Hi Jason,

Andreas had also posed a question about the length of the tables for different Re Numbers. I have run into this issue myself where I had different length airfoil tables and I ended up using AOA values common to all tables to get FAST to work. Can Aerodyn accept multiple length tables like WT-Perf?

Regards,

Subin.

8

Dear Andreas and Subin,

The current version of AeroDyn requires that an airfoil data file with multiple Reynold’s numbers use the same AoA discretization for each value of the Reynold’s number. In WT_Perf, the AoA discretization may be different for different Reynold’s numbers. We are working on a new version of AeroDyn that uses the same airfoil data format as WT_Perf, but this version will not be availabe in the immediate future.

Best regards,