XFoil airfoil data "Non-Converged"

Wind & Water Airfoils
1

Everyone,

This question is related to Airfoil Cl,Cd generation using Xfoil.

After reading many threads I came to know, airfoil files can be generated using “Xfoil” and “AirfoilPrep_v2.02.01.xls”
(Stall angle could be zero for wind load calculations)

I tried few airfoils with Xfoil for different Reynold’s numbers. All my output are matching with airfoiltools.com results. I am convinced.

But when trying S806A airfoil (Re 2E6), XFoil is not producing good results. (Upto re 1E6 results are available in airfoiltools.com)
Can anyone try this with XFoil and let me know where I am failing?

Here are the steps I tried in Xfoil.
load, pane, oper, visc, 2E6, alfa 0, iter 100, alfa 6

I get “Non - Converged” result.

Thanks
Raj

2

Raj,

I know of no one here at NREL that actively uses Xfoil. Maybe someone from the larger community can help you.

Marshall

3

Marshal,

Thanks for the reply.

What is the method used by NREL community for finding Cl, Cd, Cm of airfoil shapes at -180 to +180 Angle of attack?

What I do is, using Xfoil I generate Cl, Cd, Cm table for -10 to 10 deg angle of attack. Then input those values in “AirfoilPrep_v2.02.01.xls” for generating Airfoil file.

Thanks
Raj

4

Raj,

I usually get the low-alpha portion of the curves from existing data and use AirfoilPrep to fill out the 360 degrees.

This is not something we do often. We don’t often model a turbine from scratch (it’s been many years for me). We usually use one of our existing models or we get models from other people when we are asked to do a loads analysis. Sometimes we have to convert models for other software (like Bladed, HAWC2, and FLEX5) to FAST, but that usually does not require creating airfoil tables.

Marshall

5

Marshall,

thanks for the useful information…

Thanks
Raj

6

Good Day Sir,

Having a similar problem for converging the data, I came across the file “AirfoilPrep_v2.02.02.xls”. I require the data from -180 to +180 so that I can input in HARP_Opt Airfoils. I tried to run the “update” button under the section “TableExtrap” but nothing happens. It just pops up the “picture tools” on the excel ribbon.

Can anyone figure out the problem that I am facing and how should I go about it. I am using Excel 2013.

Thank you,

Pranav

7

Dear Pranav,

Thanks the post. We learned that the macros were broken with the release of AirfoilPrep_v2.02.02.xls. We have now fixed the macros with the release of AirfoilPrep_v2.02.03.xls, which is now available from: nwtc.nrel.gov/AirFoilPrep.

Sorry for the trouble.

Best regards,

8

While doing airfoil analysis on Xfoil, should i consider the Mach values for the Reynolds number range of 30,000 to 100,000. for small wind turbine applications

9

Dear Suni,

Compressibility effects are usually negligible in wind turbine airfoil applications, but check the Mach number if you are concerned about your given application.

Best regards,