Sonic boom in water?
I have been wondering if a displacement hull that moves fast enough
would create a sort of "sonic boom" just as an object moving fast
enough in air does. In air, the shock is created when the aircraft
moves too fast for the air to get out of the way. In water, a
displacement hull attempts to climb its bow wave which effectively
limits its speed. Apparently, this hull speed is not a mathematical
limit but merely a practical limit as sufficient power can move a hull
over hull speed. However the power necessary to produce any further
increase in speed radically increases above hull speed. If you did
manage to produce enough power, could you power through the bow wave
and thus produce a shock wave? |
dbohara
Jan 20
2006
|
| 741 mph in air at normal sea level pressure. In water at the surface, and
for a long ways down, the density does not change much, the speed of sound
would be 3000+ mph. Is why when diving, you can not tell which way a boat
or sound is coming from. Ears, are not built to differentiate the time
difference between the ears at those speeds. Air gets out of the way at
supersonic speed, or the plane could not get through the air above the speed
of sound. Sound is a pressure wave, and at the speed of sound all the
pressure of the sound waves, piles up on the plane. So lots of buffeting
and control surfaces lack response. Above the speed of sound, the
pressure wave falls away from the plane to the rear. Similar to the bow
way, now that I think about it. You have to climb the wave,and after you
start to plane, you have left the bow wave behind. Takes power to overcome
the bow wave pressure, but once on plane, you would require less power to
stay on top. Of course to get on plane, you have to use enough power to
lift the boat vertically some distance. |
Calif
Jan 22
|
| The eventuality of a "sonic boom" underwater may not be that far off. The
Russian supercavitation torpedo, the Shkval, has a speed of 350 km/h, and
was operational in the '70s. The German Barracuda being developed is
expected to reach 800 km/h. Supercavitation may be old technology. With
magnetohydrodynamic torpedoes, speeds of 1700 mph may have already been
reached. http://www.defensetech.org/archives/001688.html http://www.fas.org/man/dod-101/sys/missile/row/shkval.htm http://saifudin.com/2005/09/04/supercavitation-a-phenomenom-god-sent-us-tht-we-hardly-know/ |
thunder
Jan 22
|
| tell the truth thunder - you live in your mothers basement and surf
the web all day right? just joking.... |
Shortwave
Jan 22
|
| Well, I don't live in my Mother's basement, but I do seem to spend more
time on this box than I should. ;-) I'd never thought of a "sonic boom"
underwater, until reading this thread. It did remind me of the Shkval,
and . . . it's truly amazing the technology we use to kill each other. It may be old news to you, but I did come across this in my readings. One
has to wonder. http://www.freerepublic.com/focus/fr/623623/posts |
thunder
Jan 22
|
| Come on, Don. I know you can do better than that! Dan |
Dan
Jan 21
|
| >would create a sort of "sonic boom" just as an object moving fast |
Maynard
Jan 20
|
|
Or a limpet mine. The shock wave is very effective once you get it
going. |
gfretwell
Jan 20
|
| Did I see you on 'Most Haunted' tonight? |
Don
Jan 21
|
| Good point...But does that mean it goes BOOM...boom? lol |
markvictor
Jan 20
|
| Are you sure of this definition? Eisboch |
Eisboch
Jan 20
|
| No |
dbohara
Jan 20
|
| Me either. Eisboch |
Eisboch
Jan 20
|
| "If you did manage to produce enough power, could you power through the
bow wave
and thus produce a shock wave?" If you did, you would be on plane, traveling over the water for the most
part, and leaving any remnant of a bow wave behind the boat. Any relation
of this phenomena to a sonic or acoustical shock wave is only academic,
since the speed of sound in water is about 5 times faster than air, so it
isn't likely that there will ever be a watercraft moving at 3500mph. |
Floyd
Jan 20
|
| I believe Skipper claimed his Bayliner came close to that speed at WOT once
while on the Sea of Cortez trying to outrun a giant Tostito. ;-) |
Jan 20
|
| Alleged Bayliner. |
Harry
Jan 20
|
| tostito as in a giant corn based chip? how is that possible? was it
carrying any added dip or guacamole? |
DownTime
Jan 20
|
| Yes.in 55 gallon drums strapped onto the deck. |
Jan 20
|
| Skipper is the added dip. I dunno about the guac, though. |
Harry
Jan 20
|
| Skipper *is* a giant Tostito! |
Don
Jan 20
|
| My impression is that a planing hull has no relation to hull speed.
Furthermore, we are not talking about the speed of compressional waves
as in sound but the much slower surface waves. |
dbohara
Jan 20
|
| well Skip,
here's a formula to help you figure out how fast you need to
travel...but this would be through water, so you'll need your submarine
for the speed run: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe2.html#c1
Speed of Sound
This link will calculate the speed your surface boat will need to
achieve (simplified)
http://www.grc.nasa.gov/WWW/K-12/airplane/airprop.html
and this link is just some awesome pics and videos of planes breaking
yhe sound barrier:
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/soubar.html#c1 A 750 mph bayliner, that's gotta be some kind of record....
markv |
markvictor
Jan 20
|
| Upon reading this thread, I got this interesting piece: http://www.sky-flash.com/boom.htm |
atl_man2
Jan 20
|
| It was faster than the speed of LIGHT......never seen.... |
atl_man2
Jan 20
|
| 3721 mph, but that would be in a submarine, not on the surface, at sea
level, the nasa standard table puts SOS at sea level in daytime at
761mph...so that is what a surface vessel would have to achieve to
break the sound barrier; even a displacement hull is still floating on
the surface of th water, so it wold be subject to gas physics.A boat on
the surface is exerting a fixed force on the water (in a perfect
world), this force remains more or less constant, varying onle due to
lift and loss of it while moving, this will not generate a fast enough
shock wave through water to cause a "sonic boom" |
markvictor
Jan 20
|
| >would create a sort of "sonic boom" just as an object moving fast |
Shortwave
Jan 20
|
