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14.11: Input additional Drag

Beside the airfoil drag and the induced drag there are additional drags. This are the fuselage drag and the interference drag, which arise by influence between fuselage and wings. In the following input fields one can enter these values manually or you can select pre-set values from a table.



In general a bubble will form at the highest position when flowing an airfoil. The length of this bubble depends on the Reynolds number. Behind this bubble the flow turns into a turbulent (swirled) form. In this bubble arises viscous drag.
Click the check-box 'Compute Airfoil with Bubble Drag' to include this drag into the vortex computation.



I many applications the fuselage drag coefficient refers to the fuselage cross-section at the thickest part of the fuselage.
In the following input field you can enter the cross-section surface in meter^2. Near the input field are Up/Down-buttons located. They can be used to change the cross-section surface with mouse clicks. A click on the right mouse button pops up a menu to set the increment between 0.001m and 1m.



The fuselage drag coefficient can be entered into the input field 'Cd_fusl'. Near the input field are Up/Down-buttons located. They can be used to change the fuselage drag coefficient with mouse clicks.
There is a third method to change the value. Move the mouse cursor into the input field and click the right mouse button.
A pull-down menu pops up and offers the pre-set values for different fuselage shapes for quick selection.
The drag coefficient seems do be quit high, but one have to take in consideration that this value is related to the fuselage cross-section, not to the surface of the airplane.



At the transitions from fuselage to wings often arise turbulences (interferences) which produce additional drag. This drag can be entered into the input field 'Interference Drag Cd_int'. Near the input field are Up/Down-buttons located. They can be used to change the interference drag with mouse clicks.
There is a third method to change the value. Move the mouse cursor into the input field and click the right mouse button.
A pull-down menu pops up and offers the pre-set values for different fuselage-wing transitions for quick selection.
The interference drag is related to the total surface of the airplane so that significant smaller values in comparison to the fuselage drag can be selected.



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