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55 votes

How is it possible for supersonic aircraft to push air out of the way?

The idea that force can only be transferred/propagated at the speed of sound is a simplification. It's a very reasonable simplification, which works in a very wide array of cases, but it's a ...
Cort Ammon's user avatar
33 votes

How is it possible for supersonic aircraft to push air out of the way?

It is only the pressure wave that can propagate at the speed of sound. This means that a molecule of "air" that is ahead of a subsonic aircraft can get pushed out of the way without hitting that ...
Pilothead's user avatar
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30 votes
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Why does this shockwave not touch the body that creates it?

After passing through the shock wave, the air still has to evade the body. If the shock-wave touched the body, the air would have to escape through infinitely thin space at infinitely high pressure ...
Jan Hudec's user avatar
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16 votes
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Can supersonic booms intensify as you fly longer?

They don't really pile up like that. The 'pile up' description of how shock waves form is pretty flawed. The shock wave forms at an angle off of the body. Generally speaking, it forms a cone off of ...
Rob McDonald's user avatar
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11 votes
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How does the X-59 achieve low-noise supersonic flight?

As of the date of this answer, the X-59 has not yet flown, but according to the designers... The ground noise is expected to be around 60 dB(A), about 1/1000 as loud as current supersonic aircraft. ...
Juan Jimenez's user avatar
10 votes

Why does this shockwave not touch the body that creates it?

In case of an infinestimally thin body in supersonic flow, the disturbances created propogate as Mach waves. However, as the the thickness of the body increases, the flow has to physically turn away ...
aeroalias's user avatar
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9 votes
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Can a supersonic plane use a subsonic wing if the nosecone shock produces subsonic airflow around the wing?

Normally, the flow speed at the wing is about the same as the speed ahead of the bow shock. Only if the fuselage is still conical and expanding at the wing station would the local flow speed be ...
Peter Kämpf's user avatar
8 votes

How is it possible for supersonic aircraft to push air out of the way?

Supersonic aircraft do not push the air out of the way in front of the aircraft. They only push it sideways out of the way after the aircraft has passed the air (for the air beside the aircraft), or ...
Penguin's user avatar
  • 4,483
8 votes
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How is the camera positioned for these plane-to-plane Schlieren images of shock waves?

Where is the camera relative to these target aircraft, and what's behind them? Straight from NASA themselves: NASA flew a B-200, outfitted with an updated imaging system, at around 30,000 feet ...
Federico's user avatar
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8 votes
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How high could modern transonic commercial transport designers reasonably push L/D ratios?

First of all, I am sceptical regarding your graph. The Fokker F-28 or the Short 360 are way too good while the Boeing 767 looks poorer than what other sources claim. Size alone helps already by making ...
Peter Kämpf's user avatar
8 votes
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Why do expansion fans cause oblique shock waves to curve?

The oblique shock exists to turn the flow. Its angle (and strength) determines the turning angle. Along the body (say a 10 deg diamond airfoil), the boundary condition dictates that the shock must ...
Rob McDonald's user avatar
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7 votes

Why does this shockwave not touch the body that creates it?

Perhaps, at the root of your question, there is a misunderstanding of the nature of a shock wave. A shock wave is a surface, an ensemble of points, where the properties of the gas change ...
MariusMatutiae's user avatar
7 votes
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Why do shockwaves progressively move aft as speed increses?

The answer is deeply rooted in the theory of compressible fluid dynamics, so for a fully satisfactory take on the matter you might want to refer to a textbook on that topic (such as Thompson or ...
cruel_summer's user avatar
6 votes
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"Fundamental of Aerodynamics" 5th editon, example about oblique shock. Is the author's solution wrong?

Continue reading, I have found the answer. Look at problem 9.3, page 663: And here is the author's solution:
Dat's user avatar
  • 990
6 votes

How does the V22 Osprey manage such high rotor speeds without shock waves?

The Osprey's engines drive the rotors at 412 RPM in heli mode or 333 RPM in forward-flight mode, according to this article. With a rotor radius of 5.8m, that puts the tip velocity at 250m/s, or about ...
aerobot's user avatar
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6 votes
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Can a transonic airfoil have two shock waves?

Very Interesting results. I must say I have never before seen such a peculiar case. Yes, theoretically it seems possible to have this situation, but it's difficult to say if this is possible in ...
jayS's user avatar
  • 918
6 votes

How are shock waves formed at fighter jet inlets when the shock wave is already formed at the nose cone?

When it is said that "flow is subsonic behind the shockwave", it is only the component of velocity perpendicular to the shockwave which is actually subsonic. Image source In a normal ...
Aditya Sharma's user avatar
5 votes
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Can a flow which is initially supersonic, become subsonic without a shock wave?

Yes, it is possible . The shockless transition from supersonic to subsonic. It has been tested both experimentally and numerical solution. Read this AIAA Paper. But in your case I would suggest you ...
Praveen Rawat's user avatar
5 votes
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What would the density profile of this shock wave look like, roughly?

The shock observed is effectively the same as the one over a wing. Compression waves are normally considered of infinitesimally small thickness, although due to the non-continuous nature of gases made ...
GSammons's user avatar
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5 votes
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Since shock waves have non-negligible viscosity, why do the normal shock relations ignore friction/viscosity?

Neglecting friction does indeed lead to inaccuracies. Those, however, are small for weak shocks, so using the equations for inviscid shocks gives a good approximation. Especially in the times before ...
Peter Kämpf's user avatar
5 votes
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What determines the angle at which a shock will form?

The angle of an oblique shock is determined by the Mach number before the shock and how much the flow turns. Usually, this is illustrated by a ramp. A 10deg ramp means the shock turns 10 degrees. ...
Rob McDonald's user avatar
  • 12.6k
5 votes
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Are control surfaces less effective at supersonic speeds?

Once past supersonic speeds, the larger the speed the larger the divot of air pressure around the plane. There are no divots around the plane. Even at supersonic speeds air keeps on following the ...
sophit's user avatar
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5 votes
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Will air in a shockwave flow outwards?

No. The shock is not high pressure. The shock is a jump in properties. The flow is higher pressure behind the shock than in front. Think of the shock as an artificial boundary where the properties ...
Rob McDonald's user avatar
  • 12.6k
4 votes
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What is the difference between a shock wave and an expansion wave?

An adiabatic expansion lowers temperature, an adiabatic compression raises temperature, analogous to the way a refrigerator and an air conditioner work. Or a bicycle pump, it gets quite hot while you'...
Koyovis's user avatar
  • 61.8k
4 votes

How is the camera positioned for these plane-to-plane Schlieren images of shock waves?

Supplementary answer: As the question mentions this NASA page shows a diagram of traditional Schlieren photography and it's the idea I had in my head. I assumed you'd need a carefully prepared light ...
uhoh's user avatar
  • 5,934
4 votes

How do a narrow airframe and canards keep supersonic shock waves from coalescing?

After a lot of digging around, I found this. ...the main noise-reduction technique is to redesign the aircraft to reshape the acoustic signature. A sonic boom consists of a double bang on the ...
Juan Jimenez's user avatar
4 votes
Accepted

Could ramjets be implemented on sub/super-sonic aircraft wings due to the shockwaves generated by them?

Regardless of the shape of the wing, ramjets only outperform turbojets at supersonic airspeed. Ramjets work because the speed of the incoming airflow is such that there is no rotating compressor/...
Koyovis's user avatar
  • 61.8k
4 votes

How are shock waves formed at fighter jet inlets when the shock wave is already formed at the nose cone?

In the Schlieren photograph you present, you can see that an oblique (slanted) shock is formed wherever there is a change in the cross-section of the aircraft profile, illustrating Aditya Sharma's ...
niels nielsen's user avatar
4 votes

Can supersonic booms intensify as you fly longer?

Even if it doesn't happen, I don't understand how ten seconds of sound waves behind you piling up would be the same shock intensity as ten minutes of supersonic flying. Sound is pressure, and sound ...
hobbs's user avatar
  • 769
4 votes

What is a shockwave, and how does it form?

At subsonic speeds, the air striking for example the nose cone of a plane can communicate the approach of the plane to the air ahead of it with a displacement wave that can move no faster than the ...
niels nielsen's user avatar

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