I agree with you totally, however the Su-35 and Su-57 are based upon speed and manoeuvrability.
the DSI intake is for lower speeds, speeds of Mach 1.7 while the Russian patent claims Su-57 has an intake for speeds up to Mach 3.
The six generation fighters are ought to have less aerodynamic controls, BVR missiles do not have a kill rate of 100% specially if the aircraft firing them can not recognize if the target is an authentic friend or foe.
What i mean is Su-57 is designed to supercruise very likely at high speeds up to Mach 1.8 and it has very likely top speeds of Mach 2.4, if materials allow it.
What are the chances F-22 will surprise a Su-57? in my opinion BVR missiles are limited in number on 5th generation aircraft, I think 6 BVR AAM will not hit 100% of the time and these aircraft will carry 2 short range AAM, in my opinion these aircraft either use speed and go back after firing their BVR missiles and go home just keeping the 2 short range in the case they need them.
So then is why the caret intake of Su-57 will allow better acceleration and faster speeds than using DSI
I agree with Ronny that at lower speeds the DSI has more practicality, simplicity, so for a lower speed aircraft like F-35 remain unseen will be more important than for Su-35 or Su-57, Stealth needs always speed, because the stealth aircraft needs to enter and exit the area where it can be detected quickly to minimize loses.
J-20 also must fly at around Mach 1.6, and the porous intake holes located in the intake cowl very likely are ways to bleed boundary layer and very likely increase pressure recovery and allow it higher speeds of Mach 1.8 or mach 2, but i do not think it will be as efficient as PAKFA aka Su-57, thus i think DSI suffer limitations in speed that force F-35 or J-20 to remain unseen longer than fighters like Su-57
The diverterless supersonic inlet (DSI) of the Lockheed Martin joint strike fighter (JSF), which operates mostly at transonic speeds, has been designed taking whatever is mentioned above into enough account. Fundamental researches on this inlet configuration have been continued since the mid-1990s.
The inlet cowl lips are so designed as to allow most of boundary layer flow to spill out of the aft notch. The DSI structure complexity has been greatly reduced by the removal of moving parts, a boundary layer diverter and a bleed or bypass system thus decreasing the aircraft’s empty weight, production cost, and requirements of maintenance-supporting equipment[1-2].
the effects of the free stream Mach number on the mass flow coefficient and total pressure recovery when D = 0º and E = 0º. As the free stream Mach number increases, the mass flow coefficient decreases, and, after reaching the minimum at Mach number 1.000, it increases. Fig.7 also shows that the total pressure rises and remains constant when the free stream Mach number is up from 0.600 to 1.000, and, afterwards, drops sharply while the free stream Mach number approaches the supersonic.
4 Conclusions A wind-tunnel test of a ventral diverterless high offset S-shaped inlet has been carried out to investigate the aerodynamic characteristics at transonic speeds. Some conclusions can be drawn as follows: (1) There is a large region of low total pressure at the lower part of the inlet exit caused by the counter-rotating vortices formed at the second turn of the S-shaped duct. (2) The performances of the inlet reach almost the highest at Mach number 1.000. This renders the propulsion system able to work with high efficiency in terms of aerodynamics. (3) As the mass flow coefficient increases, the total pressure recovery decreases; the distortion increases at Ma0 = 0.850, but fluctuates at Ma0 = 1.000 and 1.534. (4) The total pressure recovery increases slowly first, and then remains unchanged as the Mach number rises from 0.600 to 1.000. (5) The performances of the inlet are generally insensitive to angles of attack from –4º to 9.4º and yaw angles from 0º to 8º at Mach number 0.850, and angles of attack from –2º to 6º and yaw angles from 0º to 5º at Mach number 1.534.
A Ventral Diverterless High Offset S-shaped Inlet at Transonic Speeds Xie Wenzhong*, Guo Rongwei College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China Received 13 September 2007; accepted 18 December 2007
Boundary-layer bleed in supersonic inlets is typically used to avoid boundary layer flow separation f_m adverse shock-wave/boundary-layer interactions and subsequent total pressure loss in the subsonic diffuser and to stabilize the normal shock
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950013353.pdf
