You can run Xfoil on your own laptop, or run it on Athena.

Running on your laptop
----------------------
Xfoil for Linux and Windows can be downloaded here:
  http://raphael.mit.edu/xfoil/

The xfoil.exe executable for Windows can be run immediately.
The Linux installation will require Fortran and C compilers.

You can probably also find an Xfoil executable for MacOS on the Web.  
Google "xfoil".


Running Xfoil on an Athena Linux box
------------------------------------

Add code locker to your path:

  % add 16_d0006               

This can be put in your .cshrc.mine file to avoid typing every session.

Start Xfoil:

  % xfoilexec

Or, start Xfoil with optional airfoil filename:

  % xfoilexec airfoil_file



Typical XFOIL session keyboard inputs
-------------------------------------

Notes:
 * Commands are shown in uppercase, but are not case-sensitive
 * Comments are shown in parentheses
 * Blank lines below are only for easier reading -- they are not Enter's!
 * A command with its argument(s) ommitted will result in an input prompt
 * A "?" command will always show the command menu at any Xfoil level


LOAD airfoil_file  (skip this if airfoil_file argument is given to xfoilexec)

NACA 0010          (can create a NACA airfoil if airfoil_file is not used)

OPER               (enter OPER menu)
?                  (show full OPER menu; commands below are from this menu)

A    5             (specify alpha; can also type full command ALFA)
ASEQ 0 8 2         (specify alpha sequence  0 2 4 6 8 )
CPV                (make spiffy Cp vector plot of last point computed, 8 deg)
CPX                (make usual Cp(x) plot again)
HARD               (write current plot to hardcopy PostScript file plot.ps; optional)
CPWR filename      (write Cp(x) distribution to text file; optional)

V   1e5            (turn on viscous toggle, with Reynolds No.; can also type VISC)
A   5              (specify alpha)
CL  0.4            (specify CL ;  corresponding alpha is computed)

P                  (turn on polar 1 accumulation toggle)
<Enter>            (decline writing to polar save file)
<Enter>            (decline writing to polar dump file)
INIT               (initialize boundary layers, since next alpha=0 
                      is very different from last-computed alpha=5 )
ASEQ 0 7 0.2       (specify alpha sequence 0.0 0.2 0.4 ... 7 )
PP                 (plot stored polar 1)
ASEQ 7.2 10 0.2    (specify alpha sequence 7.2 7.4 ... 10 ; this extends polar 1)
PP                 (plot stored polar(s)s again)
HARD               (write current plot to PostScript file plot.ps; optional)
P                  (turn off polar 1 accumulation)

RE  2e5            (set new Reynolds number)
P                  (turn on polar 2 accumulation toggle)
<Enter>            (decline writing to polar save file)
<Enter>            (decline writing to polar dump file)
INIT               (initialize boundary layers, since next alpha=0 
                      is very different from last-computed alpha=14 )
ASEQ 0 10 0.2      (specify alpha sequence 0.0 0.2 0.4 ... 10 )
P                  (turn off polar 2 accumulation)

PSUM               (summary listing of all stored polars)
PP                 (plot all stored polars)

PWRT 1             (write polar 1 to a save file)
 filename_1        (give polar save filename)
PWRT 2             (write polar 2 to a save file)
 filename_2        (give polar save filename)

<Enter>            (go back to main Xfoil menu)
QUIT               (exit program)


Note: If you ^C out of Xfoil rather than use QUIT, the Postscript file 
        may not be terminated properly and may be unprintable.


Back at the Athena prompt:

 % ghostview plot.ps          (preview plot.ps file; optional)
 % lpr -h -Pprinter plot.ps   (print plot.ps file)