The discussion revolves around the effects of a plane slowing down from hypersonic or supersonic speeds, particularly focusing on the behavior of shockwaves during this transition. Participants explore concepts related to shockwave generation, vehicle stability, and the nature of sound barriers in the context of aerodynamics.
Participants do not reach a consensus on the specifics of shockwave behavior when a plane slows down from supersonic speeds. Multiple competing views and uncertainties remain regarding the nature of shockwaves and the effects of deceleration.
Some statements rely on assumptions about the behavior of shockwaves and the conditions under which they are generated or dissipated. There are also references to external sources that may influence interpretations of the phenomena discussed.
Mustafa Bayram said:slowing down from hypersonic speed
At, or above, the speed of sound, shockwaves radiate energy from the aircraft.Mustafa Bayram said:Is it results in a new shockwave or does the shockwave continuously created by hypersonic flight suddenly disappear?
didn't know that thanks, I mean supersonichutchphd said:"Hypersonic" is usually defined as above Mach 5. "Supersonic" is defined as above Mach 1. Is that what you mean?
one of my students asks if a second shockwave is created when a plane slows down from a supersonic flight. I think this can be a good answer; a continuous shock wave created at equal or above the speed of sound. when it slows down from the speed of sound vibrations downgrade and the shockwave is disappear.boneh3ad said:I don't really understand the question. There will always be a shock of some kind at the leading edge/tip of a vehicle if ##M>1##, and that shock will smoothly change in character as a vehicle accelerates or decelerates through various Mach numbers unless conditions are near the shock detachment point. In that situation you might get abrupt changes between attached oblique shocks and bow shocks.
But that's not what I said. I'm not sure what you mean by "vibrations downgrade." I didn't even mention vibration.Mustafa Bayram said:one of my students asks if a second shockwave is created when a plane slows down from a supersonic flight. I think this can be a good answer; a continuous shock wave created at equal or above the speed of sound. when it slows down from the speed of sound vibrations downgrade and the shockwave is disappear.
Yes, I think there is a common misconception around that the boom you hear is the plane breaking the sound barrier - as if there's no boom for an already supersonic plane. That isn't correct; the boom is just the continuously created shock wave passing you as it sweeps across the ground/sky.Mustafa Bayram said:one of my students asks if a second shockwave is created when a plane slows down from a supersonic flight. I think this can be a good answer; a continuous shock wave created at equal or above the speed of sound.
So, I take that to mean that one observer will hear a bang but the next guy along the road will not but no one will hear the bang 'stopping' lol. Makes sense, though; a set of recordings made along the path of the aircraft will have a range of different bangs - the last ones would be a 'quieter bang' perhaps.Lnewqban said:Copied from
https://www.grc.nasa.gov/www/k-12/airplane/mach.html
"There is no upstream influence in a supersonic flow; disturbances are only transmitted downstream."
There is only one impulse wave travelling over the ground (or perhaps a double). Before it arrives, you don't hear it. When it passes you, you hear it. When it's gone past you no longer hear it cos it's going away from you.DaveC426913 said:I might be easier to visualize what happens (at least for me) if one realizes that the only reason that a plane slows down at all is due to the drag caused by that onrushing air. The engines power down and the force on the leading edges of the craft cause the craft to slow, allowing the shockwave to advance, smoothing out the gradient.