What is up with the F-35’s wingtip vortices?
I have next to no knowledge in the field of aerodynamics- I stumble to explain the two competing theories of how a wing works, how coupled and uncoupled canard-deltas differ – even the simple equations of Energy Management have me stumped (not even sure this last one solely exists in aerodynamics). So I’m hoping that some bright aerodynamic engineer can help me with this one – ideally using simple language. Why does the F-35 produce such distinctive vortices from the wingtip/flap edge – and are they intentional, and positive in effect? Agile fighters – with strakes or canards – display visible vortices on the inner section of the wing- presumably where it’s wanted. I thought that wingtip vortices caused induced drag and were best avoided? Yet, the F-35 seems to stream them like a ’70s airliner. Educated comments in the reply section are VERY welcome. 
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I have a friend who used to fly for the Marines. I will pass this to him and see what he has to say. He is a smart guy.
Here we have surfaces with above a low pressure and under a high pressure; when these two areas are touching (wingtips) creates a vortex; the vortex is always present; sometimes the vapor trail makes it visible, when conditions allow the formation. In this case wingtip and the edge of the flap work as two separate surfaces generating separate vortices; drag maker, unintended but inevitable.
Designers to exploit aerodynamic purpose the energy of these vortices with strakes and with canard (coupled canard).
Corrado fron Italy, with google translater help 😉
really just the humidity that day
must not be for drag….must disrupt radar signals….uh..uh..for stealth
It looks like there’s one coming off the flap and one off the wing tip.
Yes, the induced drag is unwanted, but the shape needed for a small radar signature was likely given priority over aerodynamic efficiency in the design of the wingtips. We’ve seen that they’ve given stealth a priority over maneuverability in the visual range dogfight tests against the F-16.
A little bit of previous discussion, maybe someone could build on.
http://www.f-16.net/forum/viewtopic.php?f=22&t=15013&start=135
I’m not an aerodynamacist either, just a jack-of-all-trades in the natural sciences. And I’ve never noticed that peculiar effect on the F35 before. I could be wrong about any of these points, but here’s my best guess:
What you’re seeing is 2 separate condensation trails, 1 from the wingtip and 1 from the gap between the flaperon & the wing. The only unusual thing about F35 is that these 2 trails are formed so close together.
The wingtip trail is formed in the low pressure core of the vortex – this will happen on any wingtip with the right combination of AOA, temperature, pressure & humidity. It is more commonly seen on fighter jets because they have high wing loading, low aspect ratio wings and frequently use a greater AOA (so there is more air trying to migrate around the wingtip). As far as I’m aware, F35 has no greater tendency to form this type of vortex than any other modern fighter jet (you can see them forming in that F18 pic too).
The other trail seems to have formed in the gap between the flaperon and the wing. High pressure air under the wing is leaking through the gap into the low pressure air above the flap. As with the wingtip vortex, this results in a rapid pressure drop and condensation/freezing. Again, I don’t think that this effect is unique to F35. It is seen less commonly than wingtip trails because it only happens when the flaps are deployed.
As far as I’m aware, most fighter jets have flaps on the inboard part of the wing and ailerons on the outboard part. Aileron edges rarely produce condensation trails because they are normally centred. So the tip & flap trails will be separated. Because F35 has full width flaperons, the flap & tip trails interfere with each other. The tip vortex goes up & over (as with any other aircraft). The flap/wing gap trail is caught up in the same vortex, following the tip trail in that “double helix” shape.
I doubt that this juxtaposition of flap & tip trails has any significant effect on aerodynamics, especially as it will only happen when the flaps are deployed (or during brief moments of extreme aileron deflection).
There was a discussion here about that very issue with a F16 also giving of its vortices in the same phot with the F35
http://www.f-16.net/forum/viewtopic.php?t=11527
Its actually an optical illusion that these are wing tip vortices. One of them is and the other is a vortices coming off the flaperon. This is because the plane has its gear down meaning it also has trailing edge flaps down creating a 2nd vortices which interacts with the one produced by the wing tip causing them to mix and give a spiralling appearance.
pure wingtip vortices here, plus some faint stuff from the strakes.
https://scontent-ord1-1.xx.fbcdn.net/t31.0-8/13738083_10208986617294532_8847526055102691901_o.jpg
test
Steven is right–also, reducing vortices is desired for efficiency reasons but eliminating them entirely is basically impossible. The geometry requirements of stealth/low-observable probably also mean that using standard methods (winglets, missile rails) to reduce them aren’t feasible.
Solution was probably just deal with a little aerodynamic inefficiency and put a bigger engine on it.
It is the smoke from all the burning R&D money, nothing to do with aerodynamics
I can’t tell you why the contrails look like that, but what I can say is, look at the F-35 in that photo.
Than landing gear is down, the horizontal stabs are in idle position, the lift fan is open, the swivel doors for the engine nozzle is open.
this F-35B is not trying to maneuver at all.
Recent airshow appearances of the F-35 specially those made by the Royal Norwegian air force have shown that the F-35 is very capable in the turn and burn department, despite what the critics have to say
Wingtip vortices are unavoidable. They arise whenever a lifting surface is placed into a stream of air at an angle. This produces higher pressure at the bottom and lower pressure at the top. At the wing tips this results in spillover of air upwards. The magnitude of drag that it’s responsible for depends mainly on aspect ratio of the wing, i.e. chord/span ratio. As such, something like a 70s airliner would probably produce less induced drag than any figher out there because of higher aspect ratio. In the picture of F-35 you see both the vortices originating from the wingtips and from the edge of the aileron, which in itself acts as a small wing. In F/A-18 the leading edge extensions produce massive vortices, because they act as tiny wings with tiny aspect ratio. Overal there is no *right* amount of induced drag to have. It’s a trade-off between aerodynamics and structural integrity of the wing.
Ptitz, unfortunately you are wrong. The vortices aren’t both originating from the wingtips. Only one of them is. The other is coming from the flaperon. They are swirling together because of the pressure difference causing the spiral of the two separate vortices.
I have raised the same issue on the net since the F35 appeared in the UK this summer. The point is, the vortices are very visible whilst the aircraft manoeuvres as well as when it is flying slow and straight in photo ops. It is not simply a feature of flying slow and dirty with flaps deployed and undercarriage down and they hang around too!
I’m not knocking the aircraft, but that can’t have been intentional.
the cancelled the F 23 for stupid contrails like this
Vorticity generation is necessary for lift. At the wingtips, the vortices merge, and the pressure at the centre of the vortex is sufficiently low for moisture condensation to take place. That is why it is possible to visualise them with the naked eye. They are then convected downstream by the inviscid flow around the frame. This happens in all airfoils, but it is only visible in certain situations (see pressure issues above).
What is the copyright on the figure, please?
I have the same question, not about flap vortices, but looks like the last generation stealth aircraft is most of the time generating visible wing tip vortices or “contrails”. I have the knowledge that in most normal aircraft the incidence of the wing changes across its lenght, at the wing tip pointing down (lower incidence). This is clearly visible on the F-16 or F-18 wingtip, and generally is intended to make the tip the last part of the wing to stall to give roll control and to reduce drag at cruise speed. Even the wing of the Spitfire was design like this. With this, looks like that the F-35 wing tip is most of the time at an high AOA, the likely reason being optimized for high speed, when AOA gets very low.
Wingtip vortices actually indicate the difference in local lift production between two sections of air; in the case of the JSF, the lift produced by short stubby wings, and the free stream air (no lift). Shows that the wing is having to generate relatively large amounts of lift (Cl) to maintain level flight at slower airspeeds. Indicates a heavy bird, strapped w/ small, inefficient wings, i.e., not a dogfighter.
There are thrusters in the wingtips. From the Rolls Royce PDF about the F-35 engine system: “Aircraft roll control is achieved using the Roll Posts mounted in the wings of the aircraft, which provide a further. 1,950 lbf of thrust each”. These thrusters use the bypass air to generate thrust which is likely why the wings are so short, the thrusters provide for more stability and maneuverability with shorter wings.
When you watch videos you can see activate during maneuvers.