The Ukrainian armed forces combined are no match for this Lady:
All males (and probably many females) in the JSDF have already surrendered to her.
Someone suggested that this change could be meant to change the aspect ratio to increase the efficiency of the intake, but I half wonder if the change in the intake geometry has more to do with aerodynamic changes with the introduction of the slope on the top of the intake. I certainly don’t think capture area has changed significantly (but we’d have to get a good measurement of the capture areas of 2001/2 and 2011).
I’m don’t think we could say for that it’s a bleed system. After all if it does seem a bit of an odd place to put one.
Even if it were a bleed system I’m not certain we could conclude that it’s necessarily a step back, but that claim is a bit relative. Are they simply implementing a better system to get more performance out of the inlet at specific flight regimes (maybe push the plane’s supersonic performance?), or are they revising the design to something less efficient but can reach their requirements because the simpler design couldn’t?
Also, plawolf on SDF posted a theory about those vents. Would would be interested to hear your thoughts on it
“A little late to the party, but I think the hexagon meshes on the side of the intakes covers an intake and an exhaust which are used for boundary layer control inside the intake.
There would be sliding doors, which may or may not also be covered by a similar mesh screen, on the inside wall of the intake.
By opening and closing one or both of those doors, partially or fully, the J20’s intake would be able to create pressure fields that push the boundary lay airflow forwards or backwards when it first hit the outside wall of the intake, which would then feed through to affect where and when the shockwaves form inside the intake, which in turn determines at what speed the airflow hits the compressor blades.
Its a pretty ingenious design, which should allow the J20’s fixed DSI to achieve similar supersonic performance as traditional variable geometry intakes while retaining all the RCS advantages of the DSI. Its not a perfect solution, because the movable doors and mechanisms needed for them would surrender much of the weight and maintenance savings a basic first gen DSI would have over a variable geometry intake, but I think the supersonic performance gains are viewed as well worth the cost compared to a basic DSI.”
The first bleed vent (L) serves to strengthen the initial oblique shockwave, the second (R) is to deal with residual boundary layer separation due to the intensity of the initial shock wave (and ingested BL) downstream of the compression bump surface. The problem arises in the supersonic regime when total pressure flow is degraded due to the interaction of the bleed system and shock waves. However, as these two vents increase the bleed flow rate, then the severity of these low pressure gradients is reduced.
The F-35 also suffered from similar problems but LM instigated (at least one) redesign of the duct itself. Even so it is probable that the duct design will still, to some extent, inhibit the F-35’s performance. If Mr. PLAwolf is trying to sell these J-20 duct modifications as some sort of highly evolved hybrid of the DSI, he’s most welcome to- but his assertions would be wrong. After all the whole idea of the DSI is a simple, elegant high pressure shock solution devoid of mechanisms and gizmos.
The passive porous elements (above) employed on the JF-17 are almost certainly due to address the flow separation imparted from the forward fuselage, remember the DSI was retrofitted. One would need very accurate dimensional data on the J-20 before one can confirm the root cause of it’s DSI problems, but I would suggest they are for similar reasons- namely in the absence of a ‘conventional’ splitter plate and BL cavity, the design and dimensions of the fuselage forebody are not conducive to a pressure gradient that efficiently deals with flow separation, not only trans & supersonic, but @ various AoA.
I would say BL bleeding vent. Location is interesting…
Then they must be having problems with the DSI. The F-35 doesn’t have a bleed system, not even a passive bleed system incorporated into the ‘bump’ itself (see porous elements on JF-17 below), this may have limited benefits for the subsonic regime but performance will degrade significantly in the supersonic.
Besides, interaction of a DSI shockwave and bleed system will result in significant flow distortion, particularly in the S-duck.
It has the opposite effect of what conventional splitter-plate diverter type fixed inlets at supersonic speeds, where the passive bleed system on the splitter plate offers significant benefits by stabilising the downstream (after-terminal-shockwave) boundary layer.
Having said that, they may be attempting to increase the bleed mass flow rate to improve the intakes’ characteristics in both sub & supersonic regimes. It certainly appears the intake has undergone a redesign which would imply it was a problem area for increased drag. This is a common problem with DSIs.
Eitherway, it definitely looks like a step backwards.
Few things I found funny in your post though.
a) you were touting an amazing 5m accuracy which was merely the range accuracy that was listed on the sign. Basically simple pulse doppler range detection.
b) the important angular accuracy is 0.5 degrees. IE a target could be as far as 10km left or right of where the radar thinks it is, bit different to 5m right, about 2000 times different in fact.[i] This beamwidth/angular accuracy spec is what I debunked you on in regards to suggesting low band radar is viable on the small aperture of the Mig-31. That and gain which is calculated by G = ρ(4πA/λ2) where p is aperture efficiency, A is area. I’m sure I don’t have to point out the relationship of longer wavelength vs smaller area right?[ii]
[i]. http://army-news.ru/2010/09/raketnyj-kompleks/ (30 угловых минут)
[ii]. http://forum.keypublishing.com/attachment.php?attachmentid=225095&d=1386704433
Amiga, you know full well I mean adverse pressure gradient and in what context, but for want of getting into very heavy fluid mechanics theory here, I’ll leave it there. We can discuss it in PMs if you like.
MiG-29, I get the feeling you’ve totally misunderstood my posts, that may be due to a language barrier. However, that’s not important because you don’t have the faintest idea of what you’re talking about and your comments on this topic are embarrassing to read (no offence but seriously).
Yeah, you’re right TR1:
http://new.militarynews.ru/story.asp?rid=1&nid=331618
However, I think it’s safe to assume that this “fully digital AESA” is definitely a close cousin of the system destined for the S-500- a hidden gem that went largely unnoticed @MAKS2013, as I’ll elaborate.
I don’t have accurate data for Nebo-M but Nebo-SVU* has a Max detection range for a 2.5m^2 target of 360km with an accuracy of 100m. Even if you took the ‘M’ to be a 50% improvement it still falls way short of ‘Demonstrator’.
It significantly outperforms Nebo and the known parameters for the current S-400 systems. I’ve rechecked the translation for the advertising placard and can confirm it states “P-band; detection range Max 1,500km; automatic target tracking/lock on (95% probability for 1m^2 targets) 600km and get this: accuracy of 5m(!!) that’s <1/3 fuselage length of a Rafale; minimum targets tracked 25. It’s target tracking range is twice the detection range of the ‘Gamma-DE (67N6E) for a similar sized target, and ‘Demonstrator’ appears to have a smaller array.
As there’s no way Si-LDMOS or bistatic transistors could deliver that range, and resolution/accuracy for that sized array it can only mean GaN.
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FD, the camo net’s to hide the T/R modules’ and number. I guess yours truly was also right about the significantly different arrangement & dimensions compared to Nebo. I think given the circumstances the reader can forgive my momentary hubris:
And Jo…
I would suggest you go pick up a radar or em theory manual or two before posting again. Can I suggest you seek some education on what happens when you mix small antenna area and width with long wavelength? The power source wasn’t the area where you went full retard on this comment. And don’t just be all sciolistic and just glance over a few buzzwords as you try (unsuccessfully) to do, actually try to grasp the concepts.
‘Who’s laughin’ now, Momma!!?
In the T-50’s intake duct, both the supersonic and subsonic diffusers’ oblique shock waves will be susceptible to [boundary layer] flow separation (including secondary flows) to the normal of the wave. Here one can see the shock wave (in pink) and perpendicular flow separation (in blue & turquoise) for transonic flow in a convergent-divergent duct:
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These turbulent conditions are significantly more pronounced for subsonic flow around an obstruction due to the adverse pressure gradient and will be further compounded in the T-50’s duct because it is short and sloped (label ‘5’ in the patent pic*), but also because of the variation in cross-sectional (highly convergent-divergent) area of the duct- as can be seen in the underside pic.
Hence, the adverse pressure gradient will result in particularly severe flow separation around the curve of the inner bulge where the MLG wheel stows. This inner bulge is an integral part of the subsonic diffuser.
Pic below demonstrates such [subsonic] conditions in a straight duct, the bulge may be steeper, but is certainly shorter compared to the T-50’s ‘wheel bulge’, but the effect will be similar:
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Bear in mind an efficient inlet duct should be able to deliver uniform and high pressure-recovery flow to the engine face, then one can imagine the sum total of super, trans & subsonic shock wave flow separation and their associated pressure fields in the T-50’s duct, will deliver nothing of the sort. This is where Sukhoi and TsAGI designers have done their overtime with ANSYS ‘Fluent’ and supercomputers.
Then I came across a very interesting CFD study which I believe holds the key to what they achieved.** Basically, they designed a downstream ‘outlet guide vane’ structure whose vane geometry “is modified to exactly match the resulting inclined static pressure field” and hence neutralise/mitigate the effects of the turbulent flow across all flight regimes. The net result is to ensure the uniform and high pressure recovery to the compressor face.
In layman’s terms, the following is what the ‘OGV’ achieves (turbulent flow in orange, bend not to be taken literally):
One should note that this ‘OGV’ theory is entirely consistent with the anomalous angle/cant of the 117 compared to that ‘thing’ in the intake, scale and what appear to be secondary vanes. It’s also consistent with the official patent description of [Device 9] being “axially offset” from the engine’s comp.
Evidently ‘D9’ is dual function and becomes a stealth screen when they make it out of CNT modified PMC. It is part of an integrated engine-duct stealth solution. JMTs.
* http://www.findpatent.ru/patent/247/2472956.html
** http://forum.keypublishing.com/showthread.php?126959-The-PAK-FA-News-Pics-amp-Debate-Thread-XXIV&p=2111127#post2111127
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