Vortex lift in highly swept conventional wings.

[ThePolishAviator]

Hello,

there is a lot of discussion regarding the inherent aerodynamic advantage of delta wing which is vortex lift, yet I have never encountered a discussion about vortex lift in more conventional wings that simply are highly swept (eg. English Electric Lightning). If the leading edges are very similar and the vortex does not travel very far inboard of the wing then in theory both highly swept deltas and conventional wings should enjoy the advantages of vortex lift.

Am I missing something here or is this indeed the case?

 

[FlyGuy369]

Hello,

there is a lot of discussion regarding the inherent aerodynamic advantage of delta wing which is vortex lift, yet I have never encountered a discussion about vortex lift in more conventional wings that simply are highly swept (eg. English Electric Lightning). If the leading edges are very similar and the vortex does not travel very far inboard of the wing then in theory both highly swept deltas and conventional wings should enjoy the advantages of vortex lift.

Am I missing something here or is this indeed the case?

Hey!

I think the easiest put answer here is that aircraft that use high swept wings (including lifting bodies) all benefit from vortex lift. A good example to add is it is often seen implemented in other ways, like an F/A-18's LERX. You may be valid in your assumption, provided that the chord notch inboard doesn't negate the effect.

 

[riggerrob]

Withold Kasper bragged about vortex lift on his gently swept BKB sailplane. He claimed very low rates of descent at steep angles of attack.
There is video on www.youtube.com of an ultralight Kasper Wing demonstrating the phenomenon.

 

[Nicknick]

Does the Kasper Wing have a special profile to achieve vortex lift generation?

I would be a great help for Canard designs if the main wing would become stall proof by Vortex lift generation.

Edit:
I found a very intresting paper about the BKB sailplane:

A new tailless sailplane

unfortunately, there are no wing vortexes mentioned.

 

[RocketJavelin]

https://twitter.com/x/status/1815526669689803046

View: https://x.com/aeropaleo/status/1815526669689803046?s=46

 

[riggerrob]

Does the Kasper Wing have a special profile to achieve vortex lift generation?

I would be a great help for Canard designs if the main wing would become stall proof by Vortex lift generation.

Edit:
I found a very intresting paper about the BKB sailplane:

A new tailless sailplane

unfortunately, there are no wing vortexes mentioned.

Witold Kasper also experimented with additional flaps on the top skin to encourage vortex separation. One spanwise flap was hinged at the leading edge to encourage formation of a lateral vortex immediately behind the leading edge.
The second spanwise flap was hinged about 75 percent MAC similar to where you would expect to find an aileron hinge or flap hinge, but the key difference was that Kasper's second flap hinged upwards to encourage a vortex above the trailing edge.

 

[Nicknick]

Witold Kasper also experimented with additional flaps on the top skin to encourage vortex separation. One spanwise flap was hinged at the leading edge to encourage formation of a lateral vortex immediately behind the leading edge.
The second spanwise flap was hinged about 75 percent MAC similar to where you would expect to find an aileron hinge or flap hinge, but the key difference was that Kasper's second flap hinged upwards to encourage a vortex above the trailing edge.

You mean, like this?

 

[red admiral]

You mean, like this?

The rearwards flap hinges backwards with another vortex behind it but otherwise yes.

I'm unclear how this arrangement was meant to increase lift rather than act as a giant spoiler and reduce lift.

 

[ThePolishAviator]

The rearwards flap hinges backwards with another vortex behind it but otherwise yes.

I'm unclear how this arrangement was meant to increase lift rather than act as a giant spoiler and reduce lift.

The air has momentum, after deploying the special flaps it would continue it's movement for a surprisingly long time. This made it possible for a *glider* to perform a fully controlled *vertical* landing. (The designer claimed a window of 10s after the flaps were engaged before the wing started to stall)

 

[Nicknick]

Im confused...How did that work???

 

[ThePolishAviator]

So when the flaps were opened 2 zones of recirculation would appear. At first they would be powered by the friction with the airstream outside the recirculation zone.

As the glider's airstream started approaching zero, the air in this zone would keep spinning only due to it's momentum, using the laminar airflow outside as a wall to bounce off.

This vortex had pressure low enough to keep the glider in the air for some time.

 

[Nicknick]

OK, at least my drawing was closer than I thought... How could this vortex survive for 10 sec? It doesn't look very for smooth for the air when flowing around. I guess the air for the underside of the wing was keeping the vortex alive. On the rear, we see a channel from the bottom to the top, which surly helped.

 

[ThePolishAviator]

The rear notch would disrupt the vortex during the descent, wouldn't really feed it. The vortex would survive the 10s only due to the inertial momentum of the air inside, it would weaken very quickly with time and at the end would separate violently.

 

[Nicknick]

Even during a vertical descent, the pressure on the underside would be higher than above and the notch could help to keep the swirl alive. Nevertheless, the 10 s limit indeed indicats, that it was more momentum related.

Long time ago (guess my late teen years), I was thinking about a wing or vehicle rear structue to keep the flow attached, today I believe it would cause quite a lot of drag...