# Homework Help: Supersonic flight

1. Nov 21, 2004

### ponjavic

Could someone try to explain to me the reason for the sonic boom that occurs during sonic flight and also the condensed water(?) coner(?) that appears behind the plane.
I've tried looking it up but I couldn't find any good explanations...

2. Nov 21, 2004

### Clausius2

What do you know about Gas Dynamics? Have you ever heard about a Shock Wave, or do you know what's the Mach Number?

I'm only trying to get information to not saying things that seem strange or unknown to you.

Go here and tell me what do you think: https://www.physicsforums.com/showthread.php?t=45265

Last edited: Nov 21, 2004
3. Nov 21, 2004

### Physik

When an aircraft flies through the sky, sound waves bouce off of the plane. When the plane flies faster than the waves, the plane makes a sonic boom sound as it flies through the sound waves. The water thats condensed on the plane then comes off at the moment of the sonic boom.

4. Nov 21, 2004

### ponjavic

Ok but this is no physical (not the word i'm looking for) explanation it's just an order of events.

5. Nov 21, 2004

### ponjavic

I know the gas law, I have taken a peek at bernoulli's equation, I have understood that when flying faster than the speed of sound the density of air is allowed to be changed (is this important).
I know what a shockwave is and 1 mach is speed of sound while 5 mach is 5*speed of sound

The other forum thread you posted unfortunately did not help me. It spoke of some singularity which I couldn't see.
I wonder if the condensation continues to follow the plane or is it just as it breaks the barrier? Because the sonic boom continues after the plane has broken the barrier....

6. Nov 21, 2004

### Clausius2

Nevermind, Ponjavic. The sonic boom is the consequence of a shock wave. Once the aircraft has reached the sound speed, the particles of air upstream the nose don't feel the presence of the aircraft structure. Thus all of them collide violently with the aircraft surface. It results on a strong increasing of pressure and temperature in the nearbies of the aircraft nose wall. The main property of such a shock wave is that suddenly increasing. In fact it is a discontinuity inside the flow field. That discontinuity is propagated across the flow field and the shock is convected along in an arrow shaped form just in front of the nose (have you ever seen that shape?). When you're on the street and hear the sonic boom, your ears are felling that jump of pressure produced by the shock extremes.

As the condensed water is concerned, I'm trying to clear it up to myself. But it is not an easy problem, because of that singularity you mentioned. I haven't understood that so far. The singularity of Prandtl-Gaulert is a singular effect of such flows into air. In fact, the condensation remains always if the pressure is small enough to condensate the vapor. The problem is behind the shock the pressure is increased, so that it would be hoped not to have any condensed vapor behind the shock.

7. Nov 21, 2004

### ponjavic

Ok that gave me a little more insight, thank you =)

8. Feb 2, 2012