If the wing's leading edge has a sufficient swept angle , then it is called a subsonic leading edge. Therefore, if the air speed is supersonic, the air speed on the wing will still be subsonic. According to the mentioned cases, can it be said that normal shock can be produced on wing in supersonic mach number as well? And the second question is, is it possible to break the sound barrier in supersonic Mach due to the fact that the wing's leading edge is subsonic and in higher supersonic much numbers the flow reach mach 1 on the wing surface ?
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$\begingroup$ This seems to confuse terminology with what's actually happening on the wing. From this source (bottom of page 4), "If the wing leading edge is swept inside the Mach cone the component of Ma perpendicular to the leading edge is subsonic; hence, the swept wing is said to have a subsonic leading edge. .... A swept wing with a subsonic leading edge behaves somewhat as a wing at subsonic speeds, although the actual free-stream Mach number is supersonic." $\endgroup$– Ralph J ♦Commented Aug 23 at 6:55
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$\begingroup$ if the airflow over the wing is subsonic, then the aircraft is transonic. $\endgroup$– Michael HallCommented Sep 22 at 14:13
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2 Answers
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Therefore, if the air speed is supersonic, the air speed on the wing will still be subsonic
Not really
Only behind a normal shock wave the flow becomes subsonic. Behind an oblique shock wave the component of speed perpendicular to the wave is subsonic but in total the flow is still supersonic, a bit slower but still supersonic. Slide 7 of this presentation gives a good overview of this:
The blue arrow is the flow before the oblique shock wave while the red arrow is the flow behind it. No matter what, $u_2$ is always subsonic, while $w_2$ always equals $w_1$ and the red arrow is always supersonic.
If we make at supersonic speed the same assumption like at subsonic speed that the lift characteristics of a wing do not depend on what happens along the span of the wing but only perpendicularly to it, then having a sweep angle bigger than the oblique shock wave makes the wing "subsonic". But only in respect to its lift characteristics: the flow on the wing is still supersonic.
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$\begingroup$ But the formation of the shock wave depends on how fast the air hits the wing's leading edge vertically. Even one of the ways to delay and reduce the power of the shock wave is the use of swept back wings. Therefore, the vertical component of Mach number that hitting the wing leading edge is not the only determinant of the amount of lift production. So can it be said that normal shock and as a result breaking the sound barrier can occur at supersonic speed? $\endgroup$– alirezaCommented Aug 23 at 21:21
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A sonic boom occurs whereever plane/object speed exceeds the speed of sound. Since speed of sound unlike light is based on variable criteria (temperature, pressure, density) average is 343 meters per second so any object not Painstakingly aerodynamic will generate some kind of boom
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$\begingroup$ The speed of light is also based on variable criteria. $\endgroup$ Commented Sep 24 at 18:15