A dogtooth in aviation is a wing or tailplane design where the leading edge of the airfoil has a noticeable notch or ziz-zaz.
PURPOSE OF DOGTOOTH
1. Many high-performance aircraft use the dogtooth design, which induces a vortex over the wing to control boundary layer spanwise extension, increasing lift and improving resistance to stall. The discontinuity created by the slat end itself sheds a plenty-strong vortex.
2. A dog-tooth postpones the stall on a swept and/or delta wing and reduces the pitch-up tendency.
HOW ITS WORK
On a plain swept wing or delta wing a vortex forms along the leading edge at high angle of attack. This happens because on a swept leading edge the airflow passes over the wing in a different manner then on a straight wing.On a swept wing the boundary layer tends to flow towards the wing tips, creating flow reversal at the tips which increases drag. At higher angle of attack this creates a sudden vortex along the complete leading edge of the wing, the aircraft is pitched up. The sudden vortex formation added so much lift that deltas were known to pitch up during turning or pull up manoeuvres and tended to make the aircraft tighten in a turn without additional control stick movement.
ADVANTAGES OF DOGTOOTH
- Introducing a dog-tooth near mid-span minimizes the pitch-up problem and flow reversal at the tips associated with highly swept wings.
- It produces a small but powerful secondary vortex that travels backward almost parallel to the airflow, forming an aerodynamic fence.
- It prevents flow reversal at the tips and tends to keep drag in check at high angle of attack, while enabling the wing to make lift
- Depending on aircraft design this vortex e.g. fence also crosses flight control surfaces giving improved control surface effectiveness. At high altitudes this feature also reduces trim drag since it makes control surfaces more effective, requiring less deflection.
A dogtooth is a small, sharp zig-zag break in the leading edge of a wing. It is usually used on a swept wing, but also on straight wings , to generate a vortex flow field to prevent separated flow from progressing outboard at high angle of attack.
Some of the best-known uses of the dogtooth are in the stabilizer of the F-15 Eagle and the wings of the F-4 Phantom II, F/A-18 Super Hornet, and CF-105 Arrow,
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