thermal layer

[rawghi]

Hi to all,
I haven't understood how thermal layer function and ho wto identify them...
in short... what is a thermal layer???!? :damn:

Thank you very much

[FooFighters]

Hi to all,
I haven't understood how thermal layer function and ho wto identify them...
in short... what is a thermal layer???!? :damn:

Thank you very much

I am not 100% sure.. but I thought thermal layer is a layer between the cold and warm water in an ocean. I'ts difficult to detect a sub in this layer because of turbulance. The depth of the layer differs.. so it's hard to tell how deep it is.

Again.. I am not 100% sure, but this is what I think it is.
I'll try to find some info on it.

[TheVillagePeople]

At one point my crew said "Passing thermal layer" like 4 times , I think it was when I was surfacing.

[rawghi]

Thank you both :)

[TDK1044]

Basically, the sunlight entering the ocean is absorbed near the surface. This surface water mixes with the cooler, deep waters as the wind and currents stir the waves. The surface layer therefore has pretty much a uniform temperature.

The temperature of seawater immediately below the top layer changes relative to depth. Each temperature change event is a thermal layer.

[EMAPhil]

http://navsci.berkeley.edu/ns401/NS401%20Fall%2006/Lecture09-Underwater%20Sound%20mjh.ppt
Some very good stuff here. Just Google on: Thermal layer sonar asdic
You will find tons of it.

(ASDIC was the British term used when they invented it at the end of WW1, don't flame me I haven't time to check the dates)

[SteamWake]

The psychic crew member will announce to you when that layer is being passed.

In real life a gizmo was used to measure the water temprature outside the ship. When there was a dramatic shift 10 to 20 degrees it could be assumed that a thermal layer had been passed.

Wether or not these gizmos were available for fleet boats is another topic for discussion.

I personally have no idea.

The layers are modeled in the game to some degree but basically just lowers your sound and sonar return signatures.

[FooFighters]

Basically, the sunlight entering the ocean is absorbed near the surface. This surface water mixes with the cooler, deep waters as the wind and currents stir the waves. The surface layer therefore has pretty much a uniform temperature.

The temperature of seawater immediately below the top layer changes relative to depth. Each temperature change event is a thermal layer.

I was on the right track :rotfl: :rotfl: :rotfl:

[ReallyDedPoet]

This is a mod regarding thermal layers:

http://www.subsim.com/radioroom/showthread.php?t=110559

RDP

[TripleDaddy]

Depending on the quality of the destroyer crews and the destroyer class, running below the thermal layer makes you neigh well invisible.

[TheSatyr]

A device came into usage on Fleet Boats around 1943 (I think) to be able to detect when a sub crossed a thermal layer. So yeah,they were able to detect them. I think it was also used to tell how deep the thermal layer was.

[SteamWake]

Depending on the quality of the destroyer crews and the destroyer class, running below the thermal layer makes you neigh well invisible.

I wouldent count on this absolutly tough.

I have been picked up through a thermal in silent running at 2 knots.

[AVGWarhawk]

As I understand it the water temp in varying degrees creates a layer(density) that vessels sensors have trouble getting through or just bounce back.

In the game, it reduces sensors on the DD looking for you. Not an absolute as I have witnessed. You still can be found.

[vindex]

My understanding is that the temperature of the water affects the way sound travels. So when a sound wave encounters a shift in temperates between layers, the wave is either defracted or dispersed or both. So whether they are pinging you or listening for your engine, the feedback will be distorted, resulting in either no contact or an incorrect position.

Is there anyone who can confirm this?

[Chock]

That's correct Vindex. Basically you can think of it as being similar to the effect of light passing through a prism.

However, it's probably more accurate to say the sound 'can' be distorted, rather than it 'will' be distorted. How much the distortion will be depends on the temperature variance, as well as other factors such as the salinity of the water. In SH4, the effect is perhaps a little too guaranteed, but all the same, it's nice that the effect is now actually in Silent Hunter.

If you want to read up on thermal layers, there's quite a bit about it on the sub Command and Dangerous Waters subsim forums, since thermal layers feature heavily in those two sims.

[TripleDaddy]

Depending on the quality of the destroyer crews and the destroyer class, running below the thermal layer makes you neigh well invisible.

I wouldent count on this absolutly tough.

I have been picked up through a thermal in silent running at 2 knots.

I did qualify it, you know.

[FAdmiral]

SH4 uses the Sim.cfg file to simulate the thermal layer. It reads something
like this (from the file):

[Hydrophone]
Thermal Layer Signal Attenuation=3.0 ;[>0], 1 means no signal reduction, 3 equals signal reduction to 33%

[Sonar]
Thermal Layer Signal Attenuation=5.0 ;[>0], 1 means no signal reduction, 5 equals signal reduction to 20%


JIM