XFOIL Airfoil Analysis

official page

Interface

  • XFOIL is an interactive program for the design and analysis of subsonic isolated airfoils.
  • Analysis is performed using text user’s interface (keyboard input).
  • ? command – displays list of available commands

xfoil main page

Load airfoil

from text file

LOAD filename.txt – load from text file

airfoil coordinate input file

NACA 4-series airfoil

NACA 0012 – create a 4 digit NACA airfoil

In XFOIL, the X and Y coordinate delimiter is mutiple space symbols, not tabs

Analysis

  • OPER – direct analysis routine

xfoil oper

Set analysis parameters

  • VISC – toggle viscous/inviscid mode. If viscous mode is enabled, enter the Reynolds number
  • Mach – set Mach number to account for compressibility effect.
  • PACC polar.txt – enables accumulation of polar to text file. All analysis runs will be stored to polar.txt textfile

Analysis at a given Angle of Attack

  • ALFA 4 – runs analysis of current airfoil at 4 degrees angle of attack
  • CPWR filename.txt – saves $C_p$ vs. $x/c$ distribution to text file

xfoil

Run analysis for series of angles of attack

runs XFOIL for sequence of angles of attack from 0 to 20 with 0.5-degree increment

ASEQ 0 20 0.5

sequence of angles of attack

Improve convergence

  • ITER – set number of iterations if XFOIL failed to converge

Example of not converged solution at 18 degrees

ALFA 18

alpha 18 not converged

Modify number of iterations. Solution converged.

ITER 50
ALFA 18

alpha 18 converged

Smooth airfoil

PANE – automatically smooth airfoil if number of points is too low. Xfoil automatically computes required number of points and their distribution.

Example of airfoil with poor quality

airfoil with poor distribution

Example of airfoil after processing

airfoil with good quality

Run Sequence

Download and run xfoil.exe

  1. LOAD GA37A315.txt – load airfoil from text file
  2. OPER – enter analysis routine
  3. VISC 3000000 – enable viscous flow analysis and set Reynolds number to 3×10^6
  4. Mach 0.3 – set Mach number to 0.3
  5. PACC output.txt – enable results accumulation to text file
  6. “Enter” – press enter to disable dump file
  7. ASEQ 0 20 0.5 – run analysis at angles of attack from 0 to 20 with 0.5 degree increment
  8. PACC – disable polar accumulation
  9. “Enter” – go to one level up
  10. QUIT – exit the program

Command sequence

LOAD GA37A315.txt
OPER
VISC 3000000
MACH 0.3
PACC output.txt

ASEQ 0 20 0.5
PACC

QUIT