From the OPER menu, you can use the "ppax" command to change the Cl, Cd, Cm, and AOA axes. You have the option of changing the min limit, max limit, and the delta between the lines. I don't like how you enter in the new values. When you type in the "ppax" command, it goes one axis at a time and doesn't give you a command prompt to enter in the new values. You have to enter the values on the blank line, following the current value line, and hit enter. Once you have all the axes limits changed you will have to use the "pplo" command on the OPER menu to replot the polar plots. If this is still confusing, I cover it in the polar plot basics video on my channel.
I obtained polars for different values of Ncrit from 4 to 12. I would like to know how I can get all of them in one plot. This way I can see the polars for all values of n one a single plot. Can someone help me? I am using a Mac and pplot doesn't seem to be recognise the polar name even when I use it correctly.
Hey! I´m also working with Xfoil in Mac OS. I have problems while saving and loading files. The executable is on the applications directory, so all the files I´m creating are saved on the users directory and if I want to load a new airfoil a have to save it there. Does anybody knows how to open Xfoil from a specific directory so I can save and load all the files on that directory.
Hey, I've been trying to load an airfoil that is not naca but it tells me it cannot be found. Where am I supposed to put it so it can work? It is right now inside the zip file inside the xfoil folder.
+Adrian Ruiz Create a subfolder in your XFoil folder called aerofoils (or airfoils, it doesn't matter). Assuming you know how to insert the coordinates of an aerofoil into a .txt file, save it as 'filename.dat' (you must have .dat at the end). Run XFoil and type 'Load' then type in the file's name, with .dat at the end. If that doesn't work, type in the file's location - ie, C:\Users\JoeBlogs\DirectoryFolder\XFoil\AerofoilsSubFolder\filename.dat That should work, but sometimes it doesn't, so try restarting XFoil :-)
if I want to make an analysis but the angle does not converge and the analysis stops, What should I do to run the full analysis with the angle range I want?
As Karthikeyan Natarajan previously mentioned, one potential solution is to increase the maximum number of iterations before performing an analysis (from the OPER menu use the "iter" command with something like 200). If you forget to do this beforehand an it stops iterating because it hit the max iteration count you can use the exclamation point command, "!", to tell XFOIL to keep iterating. Another possible solution is to change the airfoil paneling by increasing the number of panels or bunching the panels around where it doesn't want to converge. I created a video all about adjusting the airfoil paneling parameters to show how this is done in XFOIL. A third possible solution is to try an angle just slightly different than the one that doesn't want to converge. For instance, if it doesn't want to converge at an AOA of 15 degrees try 14.99 degree or 15.1 degrees. Sometimes with numerical approximations, certain conditions will cause the analysis to jump back and forth between two numbers without converging (not as common as other issues) and doing a similar number that is slightly different will converge. A final solution is that it might not be a possible solution. If you try and prescribe a coefficient of lift above the max coefficient of lift that would be an invalid condition. So you might want to also ask yourself if it is supposed to converge at that point.
Hello, I installed Xfoil and XQuartz onto my Mac, however, I having an issue in getting it to load a text file. Do I need to have Xfoil/XQuartz and load file in the same folder i.e. applications? Thanks
you type "load (file pathname)" if you're using mac, select the file wherever it may be and hit command+option+C to copy the pathname to get the exact pathname of the airfoil data
When you use the PACC command to toggle on the point accumulation, before using the ASEQ command to generate your polar points, XFOIL will prompt you to enter in the polar save filename (step 7 in my polar plot basics video). If you enter in a filename, like NACA4412_polar.txt , then the software will not only turn on polar point accumulation but it will also save the data from each point of the ASEQ (AOA sequence) into the file automatically. You can then open this file using any .txt program and see the CL, CD, CDp, Cm, Top_Xtr, and Bot_Xtr for each angle of attack you ran the analysis at. If you run into problems, check out the video I did on the polar save/dump files where I cover some of the finer details. Hope this helps!
Made by Mark Drela AND Harold Youngren actually.
I personally prefer DesignFoil for airfoil analysis.
Would you say the money is worth it?
How to get result from Xfoil in Matlab without window of Xfoil being opened ?
hey, did you figure out how to strech out the boundaries for the cl(alfa) plot? you are talking about it in minute 14:00. thanks!
From the OPER menu, you can use the "ppax" command to change the Cl, Cd, Cm, and AOA axes. You have the option of changing the min limit, max limit, and the delta between the lines. I don't like how you enter in the new values. When you type in the "ppax" command, it goes one axis at a time and doesn't give you a command prompt to enter in the new values. You have to enter the values on the blank line, following the current value line, and hit enter. Once you have all the axes limits changed you will have to use the "pplo" command on the OPER menu to replot the polar plots. If this is still confusing, I cover it in the polar plot basics video on my channel.
I obtained polars for different values of Ncrit from 4 to 12. I would like to know how I can get all of them in one plot. This way I can see the polars for all values of n one a single plot. Can someone help me? I am using a Mac and pplot doesn't seem to be recognise the polar name even when I use it correctly.
Make a tutorial for MAC xfoil doing an analysis that is NOT naca.
Hey! I´m also working with Xfoil in Mac OS. I have problems while saving and loading files. The executable is on the applications directory, so all the files I´m creating are saved on the users directory and if I want to load a new airfoil a have to save it there. Does anybody knows how to open Xfoil from a specific directory so I can save and load all the files on that directory.
Hey, I've been trying to load an airfoil that is not naca but it tells me it cannot be found. Where am I supposed to put it so it can work? It is right now inside the zip file inside the xfoil folder.
Adrian Ruiz If the file is just in the xfoil directory (the same as xfoil.exe) then it should work
+Adrian Ruiz Create a subfolder in your XFoil folder called aerofoils (or airfoils, it doesn't matter). Assuming you know how to insert the coordinates of an aerofoil into a .txt file, save it as 'filename.dat' (you must have .dat at the end). Run XFoil and type 'Load' then type in the file's name, with .dat at the end. If that doesn't work, type in the file's location - ie, C:\Users\JoeBlogs\DirectoryFolder\XFoil\AerofoilsSubFolder\filename.dat
That should work, but sometimes it doesn't, so try restarting XFoil :-)
well done, very nice tutorial!
if I want to make an analysis but the angle does not converge and the analysis stops, What should I do to run the full analysis with the angle range I want?
kindly increases the number of iterations. that could solve your problem
As Karthikeyan Natarajan previously mentioned, one potential solution is to increase the maximum number of iterations before performing an analysis (from the OPER menu use the "iter" command with something like 200). If you forget to do this beforehand an it stops iterating because it hit the max iteration count you can use the exclamation point command, "!", to tell XFOIL to keep iterating.
Another possible solution is to change the airfoil paneling by increasing the number of panels or bunching the panels around where it doesn't want to converge. I created a video all about adjusting the airfoil paneling parameters to show how this is done in XFOIL.
A third possible solution is to try an angle just slightly different than the one that doesn't want to converge. For instance, if it doesn't want to converge at an AOA of 15 degrees try 14.99 degree or 15.1 degrees. Sometimes with numerical approximations, certain conditions will cause the analysis to jump back and forth between two numbers without converging (not as common as other issues) and doing a similar number that is slightly different will converge.
A final solution is that it might not be a possible solution. If you try and prescribe a coefficient of lift above the max coefficient of lift that would be an invalid condition. So you might want to also ask yourself if it is supposed to converge at that point.
Hello, I installed Xfoil and XQuartz onto my Mac, however, I having an issue in getting it to load a text file. Do I need to have Xfoil/XQuartz and load file in the same folder i.e. applications? Thanks
Having the same problem, anyone got an answer for this?
you type "load (file pathname)" if you're using mac, select the file wherever it may be and hit command+option+C to copy the pathname to get the exact pathname of the airfoil data
thanks!!! I was freaking out with it
thanks i looked everywhere for this
Thankyou!
How can I save all the coefficient values in a text file?
+luiz I've found it. For those with the same doubt, the command is "pacc". You just have to type the filename after that.
Thanks!
When you use the PACC command to toggle on the point accumulation, before using the ASEQ command to generate your polar points, XFOIL will prompt you to enter in the polar save filename (step 7 in my polar plot basics video). If you enter in a filename, like NACA4412_polar.txt , then the software will not only turn on polar point accumulation but it will also save the data from each point of the ASEQ (AOA sequence) into the file automatically. You can then open this file using any .txt program and see the CL, CD, CDp, Cm, Top_Xtr, and Bot_Xtr for each angle of attack you ran the analysis at. If you run into problems, check out the video I did on the polar save/dump files where I cover some of the finer details. Hope this helps!