J-20 5th Gen Fighter Thread V

[Blitzo]

*Googles PDS Aperture... comes back empty-handed...
Benn lurking this forum for several years now, still get some unkonw term from time to time :S

PDS: passive detection system

 

[no_name]

That top view of the J-20 makes it look like the vortex is being pulled inward into the body rather than dissipating outward toward the wing?

I think it's just the angle and it runs more or less parallel down the length of the wing. In addition I remember reading the plane designer said that the vortex generated by the LERX is designed to pass outside the v tails otherwise it causes instability issues.

 

[no_name]

View attachment 13643

Would made a great top view pic if someone had snapped a high def closer-up.

 

[latenlazy]

I think it's just the angle and it runs more or less parallel down the length of the wing. In addition I remember reading the plane designer said that the vortex generated by the LERX is designed to pass outside the v tails otherwise it causes instability issues.

This is the image I'm talking about. Doesn't think it's running parallel.

View attachment 13643

 

[no_name]

Are you sure that is a vortex visible or just the wing-fuselage connection.

Here's some photos I've found and they all go outwards away from tail:

Here's one of the F-22:

J-31:

 

[Air Force Brat]

This is the image I'm talking about. Doesn't think it's running parallel.

no name is talking about the first picture with the vortex off the canard, that vortex bisects the leading edge of the main wing at the inboard leading edge of the leading edge "slats/flaps". That is intentional, and it energizes the flow behind the leading edge slat, as well as keeping the airflow "attached" to the upper surface of the wing.
your image shows the vortex off the outboard trailing edge of the main wing, that does NOT contribute to lift as it is unable to affect the airflow in any meaningful way.

no name, that vortex runs parallel to the direction of flight, also note that the canards are not deflected, but that the trailing edge flaperons/elevons are deflected upward, pushing the tail down and the nose up, the aircraft is in an approximately 65 degree bank, the elevon on the lower main wing trailing edge is deflected upward slightly more than the elevon of the top wing to counteract the "overbanking" tendency in very tight turns, were it not deflected upward the aircraft would tend to increase the bank angle?? lots of good information here, but there would be a lot more if we had a little blue smoke showing us the whole airflow around the aircraft, its quite fascinating.

 

[Air Force Brat]

Are you sure that is a vortex visible or just the wing-fuselage connection.

Here's some photos I've found and they all go outwards away from tail:

note that in both of these pictures the canard is angled downward even though it is quite obvious that the airplane is pulling positive gs as it "climbs" into the turn, the vortex we see here is off the trailing edge of the forward lifting body fuselage, the forward fuselage makes very significant lift, that vapour vortex is off the outboard foreward induction inlet??? WOW! these are great pictures and "show" you the lift, as well as the turbulent energized "flow". The elevons/flaperons are deflected upward to hold the airplane into the turn.

 

[no_name]

There is another one here, all these were old 2001-2004 prototypes.

 

[Richard Santos]

This kind of vortex trail forms wherever there is a lifting surface with an edge that is parallel or nearly parallel to the direction of travel. Such an edge on any lifting surface of a aircraft could be there by design to create the vortex, it could also simply be unavoidable due to other design considerations. Basically the pressure difference between upper and lower surfaces of lifting surface allows the air to curl around the edge of lifting surface, the spinning motion of the air as it curls around is what creates the vortex.

 

[latenlazy]

Are you sure that is a vortex visible or just the wing-fuselage connection.

Here's some photos I've found and they all go outwards away from tail:

Here's one of the F-22:

J-31:

Pretty sure that's a vortex trail in the top view picture I quoted. Keep in mind that this is the first set of pictures we've had of the 201X series with vortices, which has different shaped vortex generators from 200X. I brought it up because we haven't seen this before. From the picture I pointed out it seems the vortex starts at the LERXes and rolls inboard along the contours of the engine nacelles.