I am working on a project and just need to understand one concept that I cannot find an answer to anywhere and hoping you could answer for me.

The project I'm working on is with airfoils and the main on NACA 63-021. In short, from what I have read as the foil get taller/thicker it creates more lift and can handle higher angles of attack as well.

My question to you is: if a foil like this which is symmetrical top and bottom foil shape, what direction of lift is increasing as the foil shape gets thicker? is the lift seen as forward motion lift/thurst?

You help on this would be greatly appreciated!

  • $\begingroup$ Try this site. I think some of the side links might get you to lift simulations. airfoiltools.com/airfoil/… $\endgroup$ – CrossRoads May 6 '19 at 23:32
  • $\begingroup$ This site has a tool you use to simulate airflow around airfoils engineersrule.com/tutorial-performing-flow-simulation-aerofoil $\endgroup$ – CrossRoads May 7 '19 at 0:06
  • $\begingroup$ Interesting to note that these thick airfoils seem to require a Reynolds number of at least 200,000 to work, which is leading me to believe the Bernoulli top lift of classic aviation lore (circulation) may have both a low and high Reynolds range. Working on this. But to answer your question, with a symmetrical, you must have an AOA to create lift. With symmetricals, you get equal performance for both negative and positive AOA, making them popular for aeobatic aircraft. However, these forgiving airfoils will create more drag at higher speeds. $\endgroup$ – Robert DiGiovanni Oct 20 '19 at 0:36

Lift is defined as the vector component of the total aerodynamic force perpendicular to the freestream velocity vector. Wikipedia about lift

By definition lift can not contribute to thrust or drag, so the direction is fixed.

The sense of the lift vector is opposite to the flow deflection caused by the angle of attack, so the lift increases in that sense.

For your project you might be interested in looking at the lift/drag profile, rather than just at lift.


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