14.1: Angle of Attack
Click the folder button 'Design Computation' and enter the desired angle of
attack into the input field 'Angle of Attack'. The dimensional unit for entered
data is 'degree' [°]. Valid values lie between -90° and +90°.
In practice angles of attack of more than 10° to 20° are not reached. With
these angles, especially with Reynolds numbers smaller then 1.000.000 flow
separation occurs.
Near the input field are Up/Down-buttons located. They can be used to change
the angle of attack with mouse clicks.
A click on the right mouse button pops up a menu to set the increment between 0.00001°
and 1°.
To see the effect of this function, it is useful to select the incident flow
vector button.
The pictures below shows a rectangular wing with 0° angle of attack. The X-axis
of this wing is equal to the angle of attack.
Enter into input field 'Angle of Attack [°]' 10° and confirm with enter. The
wing will now be pitched, X-axis of wing and incident flow vector differ.
If no actual vortex computation is present, the input fields are shaded in red.
After vortex computation the background colour of input fields is white.
Below the input fields the button 'Start Computation' is located. If you click
this button, the Vortex-Lattice computation will start. This computation runs
twice, first with an angle of attack tightly above the selected angle, and
afterwards with the selected angle. These two computations are necessary to get
a stability measure.
A successful vortex computation fills the five design computation fields on the
left side of the 'Design Computation' folder. You find there Design Cl, the
stability measure l_my, centre of gravity (referenced to the airplane's
zero-point) and the airspeed which is necessary to keep the airplane on a
straight and level flight.