SUBSIM Radio Room Forums - View Single Post - Sonar experts: How much sound crosses a layer?

OKO · 11-26-05, 11:26 PM

I took this screens with a scenario I made 8 month ago
i used twice the same scenario, just changed the speed of the KILO.

Whether you like it or not, I got this result.
Now try something if you don't believe me =>
desinstall DW and reinstall it without patching
then proceed to this very simple verification : put a KILO at 1000 ft and do the test.
I did it with both KILO and 688i and had the same result, but I can't remember the speed at which the 688i started to make big noise, this test was made 8 month ago, BEFORE the sound fix.
Anyway, this is another subject, I don't care about older values, i care about actual ones, which are wrong.

About turbulence, I explain you what I COULD SEE each time i'm sailing, this mean beetween 4 and 6 times a year.
but maybe you have more experience than me on this subject, even if I sail for 35 years on many different ships.
Now, as I see you don't even trust me about my tests (at least you didn't said I lies ...) I don't see any reason to continue this discussion ...

but fact are :

1) ANY NAVAL HULL in the world, made by human (i don't know about ET ones ...) have a critical point at which turbulence start to be created, and this point depends DIRECTLY to the type of hull (the form and the length) and allow most mdern ship to have best performance (ie step forward) in this matter, because more research was made to delay this critical point.

2) at this critical point, the non linear flow not only produce turbulence but start also to reduce the hydrodynamical performance of the ship (mean it need more power than before to increase the speed), if you stll don't believe me, just read some physics basics.

3) when turbulence are created, not only more opposition to advancing is generated, but also NOISE is generated, and MUCH MORE NOISE than before turbulence occurs.
Simple example is the washout on sonar when you reach 14knts with the 688i, when it is 8 knts with the Akula
You didn't ask yourself why there is difference here ? it's mainly due to the hull hydrodynamical performance, not only the sonar sensitivity.

4) NOTHING OF THIS is modelised in actual DW nor LWAMI, and didn't even approach this, all sound profiles are absolutly linear actually, that is not correct and not realistic.

5) I never said original was realistic, but i said It was closer to the real thing than what we have actually, because i could saw a gap I don't see anymore in the actual DW with sound fix

You see, military are actually trying to reproduce the skin of the shark to use it for subs skins, and on competition sailing boats, and you know why ?
guess ...
to delay to the maximum the time the turbulence start to be generated.
because when turbulence start to be generated, this degrade the hydrodynamic performance and cause NOISE.

So actually, our sound profile for subs are not realistic.
whether you like it or not ...

11-26-05, 11:26 PM	#8
OKO Commander Join Date: Jan 2002 Location: Solar system, mainly on earth Posts: 476 Downloads: 62 Uploads: 0	I took this screens with a scenario I made 8 month ago i used twice the same scenario, just changed the speed of the KILO. Whether you like it or not, I got this result. Now try something if you don't believe me => desinstall DW and reinstall it without patching then proceed to this very simple verification : put a KILO at 1000 ft and do the test. I did it with both KILO and 688i and had the same result, but I can't remember the speed at which the 688i started to make big noise, this test was made 8 month ago, BEFORE the sound fix. Anyway, this is another subject, I don't care about older values, i care about actual ones, which are wrong. About turbulence, I explain you what I COULD SEE each time i'm sailing, this mean beetween 4 and 6 times a year. but maybe you have more experience than me on this subject, even if I sail for 35 years on many different ships. Now, as I see you don't even trust me about my tests (at least you didn't said I lies ...) I don't see any reason to continue this discussion ... but fact are : 1) ANY NAVAL HULL in the world, made by human (i don't know about ET ones ...) have a critical point at which turbulence start to be created, and this point depends DIRECTLY to the type of hull (the form and the length) and allow most mdern ship to have best performance (ie step forward) in this matter, because more research was made to delay this critical point. 2) at this critical point, the non linear flow not only produce turbulence but start also to reduce the hydrodynamical performance of the ship (mean it need more power than before to increase the speed), if you stll don't believe me, just read some physics basics. 3) when turbulence are created, not only more opposition to advancing is generated, but also NOISE is generated, and MUCH MORE NOISE than before turbulence occurs. Simple example is the washout on sonar when you reach 14knts with the 688i, when it is 8 knts with the Akula You didn't ask yourself why there is difference here ? it's mainly due to the hull hydrodynamical performance, not only the sonar sensitivity. 4) NOTHING OF THIS is modelised in actual DW nor LWAMI, and didn't even approach this, all sound profiles are absolutly linear actually, that is not correct and not realistic. 5) I never said original was realistic, but i said It was closer to the real thing than what we have actually, because i could saw a gap I don't see anymore in the actual DW with sound fix You see, military are actually trying to reproduce the skin of the shark to use it for subs skins, and on competition sailing boats, and you know why ? guess ... to delay to the maximum the time the turbulence start to be generated. because when turbulence start to be generated, this degrade the hydrodynamic performance and cause NOISE. So actually, our sound profile for subs are not realistic. whether you like it or not ...