I'm working on inviscid analysis flow in XFOIL. The trailing edge of my airfoil is too sharp, therefore leading to non-convergence of the analysis. Modifying the trailing edge thickness may do the trick. How to adjust the trailing edge thickness in XFOIL? I read online that you have to use the command GDES > TGAP. However, I couldn't find anything regarding of what to input the command. The documentation was not helpful either. I would like to change the thickness to 20% of the chord length.
$\begingroup$ Where do those 20% come from? Is that a typo, or is it a root airfoil for a wind turbine? The latter can be truncated for transport reasons. $\endgroup$– RaketenolliFeb 12 at 3:28
XFOIL is happy with a sharp trailing edge and will tolerate a gap of a few percent. However, 20% is way beyond of what it is meant to receive as input, so I would not trust the result.
How to adjust the trailing edge thickness in XFOIL?
From the starting point you should first load an airfoil (for my example I used the command
NACA 2412 to get a simple NACA four-digit airfoil).
Then I changed into the geometry design subset with
gdes and continued like this:
.GDES c> tgap Current gap = 0.00252 Enter new gap r> 0.02 Enter blending distance/c (0..1) r> 0.1 Max thickness = 0.120041 at x = 0.297 Max camber = 0.019999 at x = 0.403 .GDES c>
The result is an overlaid plot of the old and the new geometry, like this:
To set a sharp trailing edge, set
tgap to zero. For this example, I continued into the operating subset and calculated the inviscid flow at an AoA of 4°:
.GDES c> tgap Current gap = 0.02000 Enter new gap r> 0.0 Enter blending distance/c (0..1) r> 0.1 Max thickness = 0.120031 at x = 0.297 Max camber = 0.019999 at x = 0.403 .GDES c> Buffer airfoil is not identical to current airfoil XFOIL c> pane Sharp trailing edge Paneling parameters used... Number of panel nodes 160 Panel bunching parameter 1.000 TE/LE panel density ratio 0.150 Refined-area/LE panel density ratio 0.200 Top side refined area x/c limits 1.000 1.000 Bottom side refined area x/c limits 1.000 1.000 XFOIL c> oper .OPERi c> alfa 4.0 Calculating unit vorticity distributions ... .OPERi c>