wen wrote:J-20 get an unique aerodynamic layouts: lifting-body canard blending in Gothic strake/leading edges.
Gothic?!! Nice name
wen wrote:The design has two very significant benefical features:
1, It will make the aircraft become highly-agile, based on Song's wind tunnel tests, when other factors are controlled, in terms of dog-fight performance/agility, lifting-body canard blending with gothic strakes (J-20)>>short-distanced coupling canards (J-10, Raflale, JAS-39, MiG-1.44)>long-distance coupling canards (EuroFighter 2000)>Large gothic leading edges (F/A-18E/F, Chengdu JF-17/FC-1)>conventional layouts(including these with small leading edges, F-22/35, F-15, Su-27, etc).
Please explain the physics behind this. When you consider conventional layouts remember to take into account elevators. What do you mean by canard being inline. Only the join is. The rest of the canard isn't.
wen wrote:2, The other primary benefits is, usually to creat large lifting force, you need large wing-span, however the large wing-span will create higher air-drag during high speed supersonic phase, which means there is some painful trade-off between sub-sonic agility and supersonic performance you have to made.
However, when you creates large part of your lift through the well blended gothic strakes instead of mostly created from the main wings like all the existing canard designs, based on Song's wind tunnel test, there will be a very special aerodynamic charater, that within certain degree, actually it will turn out to be, the LOWER the wing-span, the HIGHER the lifting force can be created.
Thus actually by designing the fighter this way, you can design a low-wingspan high-lifting fighter which is BOTH optimized at dog-fight AND supersonic performance.
Really, is this the reason? Remove the canard and main wing. Replace the main wing with the same wingspan and chord equal to chord of present wing + present canard. You will have more lift than the present configuration with the same wing-span!
And did you know that a lifting canard creates upload which has to be balanced by extra lift of the wing?
Also, for pitch stability, the main wing can never reach its maximum lift capability. Hence, the main wing must then be larger than on the conventional configuration, which increases its weight and profile drag.
Read about aspect ratio,wave drag and vortex shedding of the canard alignments and then analyze you would see the real reason of the canard and its alignment. Let me know when you are ready to discuss. Have you read about other possible configurations and their benefits? If not, I advice you to read. Don't make a fool of yourself till then. I am not going to waste my time on you unless you bring something meaningful to discuss. In hindsight, I think this discussion is a big waste of time for me.
The title of this paper, translated in English, is "A LOW WINGSPAN HIGH LIFTING, HIGH AGILE DESIGN OF THE NEXT GENERATION FIGHTER".
I am surprised why this paper was not submitted to any renowned journal. Oh ya! all these are known concepts and a journal paper is supposed to carry something novel.
For your information, planes with lifting canard in history:
Wright Flyer (the first plane ever)
The lifting canard has many drawbacks. There was a reason why people went away from a lifting canard to elevators. But a lot depends on the configuration. The J-20 has an interesting configuration, but kinematic-ally it won't match the F-22 or the PAKFA. Learn more about aerodynamics and then we can talk.