Breaking the sound barrier...

[beansbaxter]

Check out this video of an F-14 breaking the sound barrier.

Video

After watching it, I dont understand the change in pressure. At sea level, a plane must exceed 741 mph to break the sound barrier. The change in pressure as the plane outruns all of the pressure and sound waves in front of it is heard on the ground as an explosion or sonic boom. The pressure change condenses the water in the air as the jet passes these waves. Why doesnt this happen father up in elevation since there is always water at some point in the air?

 

[Geniere]

Beansbaxtor ? As I understand it, the plane does not outrun the pressure and sound waves in front of it. The air is compressed by the leading edges of the plane. This ?shockwave? propagates outward at the speed of sound. Below mach 1, the pressure wave acts on the air molecules in front of the plane so as move them away from the leading edges and cushions the transition. At and above mach 1, the leading edges impact on the air molecules directly. This causes an immense high-pressure region that is then heard as a sonic boom. The boom does not occur as a single event, it is a continuous phenomenon as long as the plane is supersonic. A ground observer will hear 2 booms, the second from the rear of the plane, as the high-pressure volumes pass by. The visible vortices are actually regions of low air pressure wherein water vapor is condensing. It is not necessary for the plane to exceed the speed of sound to generate vortices; it merely requires the negative pressure to be below the partial pressure of water. The vortices are usually generated from the trailing edges of the plane. Cavitations from a ship?s propeller are due to a similar cause. Visible vortices are not altitude dependent but the negative pressure must be blow the surrounding partial pressure of water to cause them to occur.

 

[kaizersose]

Originally posted by: Geniere
....It is not necessary for the plane to exceed the speed of sound to generate vortices; it merely requires the negative pressure to be below the partial pressure of water vapor in the surrounding air. The vortices are usually generated from the trailing edges of the plane....

there is your answer.

sweet video by the way, where did you get it?

 

[FasterCPU]

Can't stay long. Just dropping in to say that this is a very interesting topic (and personally have zero expertise in this area). Check out the Prandtl-Glauert Singularity condensation cloud photos at http://chamorrobible.org/gpw/gpw-20040817.htm (August 17, 2004) and at http://chamorrobible.org/gpw/gpw-20040818.htm (August 18, 2004) . WARNING: These photos are stunning. Examine at your own risk!

 

[FasterCPU]

Originally posted by: FasterCPU
Can't stay long. Just dropping in to say that this is a very interesting topic (and personally have zero expertise in this area). Check out the Prandtl-Glauert Singularity condensation cloud photos at http://chamorrobible.org/gpw/gpw-20040817.htm (August 17, 2004) and at http://chamorrobible.org/gpw/gpw-20040818.htm (August 18, 2004) . WARNING: These photos are stunning. Examine at your own risk!

The August 17, 2004 link wasn't pointing to the right place, but now is; both in the quote above and the original post. My apologies for not catching the typo earlier. It probably would be helpful to mention that the link for the August 2004 archive can be found at http://chamorrobible.org/gpw/gpw.htm (don't want to take any chances of typing that wrong!); and that the August 17, 2004 and August 18, 2004 photo collections are linked to each other, i.e., click on the "Month Day, Year" subtitle at the top of the page and it will take bring up August 17, 2004 (if you're already on August 18, 2004) or August 18, 2004 (if you're already in August 17, 2004).

That said, the WARNING given above still applies, now doubly so!

 

[Geniere]

Welcome!

Nice pics.

 

[earthling30]

Cool video! I only wish I could find a picture with a jet flying at high speed close to the waters surface and the water is literary picked up and swirled from the turbulance. Does anyone know where I can find this picture. This picture is cool, come to think of it, I believe that one that I'm talking about was a picture of a F-14 Tomcat doing this. I've googled it but know luck.

 

[Geniere]

Firefox - Clint Eastwood????

 

[earthling30]

Originally posted by: Geniere
Firefox - Clint Eastwood????

Well........Sort of like that from what I can remember from the movie (it's been a very long time since I've seen it), but what I've seen had an F-14 Tomcat doing it over water.

 

[FasterCPU]

Originally posted by: earthling30

Originally posted by: Geniere
Firefox - Clint Eastwood????

Well........Sort of like that from what I can remember from the movie (it's been a very long time since I've seen it), but what I've seen had an F-14 Tomcat doing it over water.

In the main caption at http://chamorrobible.org/gpw/gpw-20040818.htm or http://chamorrobible.org/gpw/gpw-20040817.htm , click on the "Prandtl-Glauert Singularity" link. It's worth going through every photo link on that page, specially the pages with the professor's explanations.

Regarding the photo you're looking for, I too recall seeing something like it. Try the following, as given, at http://google.com: "blue angels" site:GalleryOfFluidMechanics.com

And visit http://www.airshowaction.com/picweek.html (found via the important "Prandtl-Glauert Singularity" link mentioned earlier), which are the pictures I recall seeing.

Hope all have seen picture #8 (the latest one) at http://chamorrobible.org/gpw/gpw-20040818.htm . In my opinion all the photos (August 17 and 18, 2004) are worth viewing by young and old, regardless of profession or educational level. They are really spectacular and undoubtedly excite ones curiosity.

 

[FasterCPU]

Originally posted by: earthling30
Cool video! I only wish I could find a picture with a jet flying at high speed close to the waters surface and the water is literary picked up and swirled from the turbulance. Does anyone know where I can find this picture. This picture is cool, come to think of it, I believe that one that I'm talking about was a picture of a F-14 Tomcat doing this. I've googled it but know luck.

One of the two new pictures in the August 17, 2004 photo collection at http://chamorrobible.org/gpw/gpw-20040817.htm (all on the bottom row) is of an F-14 with a condensation cloud that catches your eye in a major way. It's #5 on the bottom row on the left. When I saw it I thought it may be the photo you're looking for. The photo doesn't look real, but the photo credit leaves no doubt that we're looking at a very real and yet another very impressive Prandtl-Glauert singularity condensation cloud.

 

[earthling30]

Originally posted by: FasterCPU

One of the two new pictures in the August 17, 2004 photo collection at http://chamorrobible.org/gpw/gpw-20040817.htm (all on the bottom row) is of an F-14 with a condensation cloud that catches your eye in a major way. It's #5 on the bottom row on the left. When I saw it I thought it may be the photo you're looking for. The photo doesn't look real, but the photo credit leaves no doubt that we're looking at a very real and yet another very impressive Prandtl-Glauert singularity condensation cloud.

Yeah sort of, but the one I'm looking for is flying very close to the waters surface................sigh, it's like trying to find needle in a hay stack.