Equivalent Air Density Depth (EADD)

edster

An additional question which may be completely irrelevant, or not - but here goes :

Is the viscosity of the gases significant to take into account - and if so, then you might need to consider the temperature of the gas that you use. After all if a 10deg C change makes water half as viscous, then I would assume that it has at least some effect on other fluids. Unfortunately I can't add much more than that, but perhaps someone else can take up the baton?

cheers

Ed

__________________

Tim Cashman

Excellent concept. Heres an additional twist.

Daltons law states that the pressure of a gas mixture is the sum of the partial pressures of the component gases.
Henry's law states that the solubility of a gas is directly proportional to its pressure.

If we use trimix 10/70/20 at 90m the ppO2 = 1bar, ppHe = 7 bar, ppN2 = 2 bar right?

Henrys law states the gas dissolved in the liquid is proportional to these individual pressures, so O2 gets metabolised and isn't a primary concern, He dissolves to the tune of 7 bar x time, N2 dissolves to the tune of 2 bar x time.
If we vary these individual pressures by changing the mix we will vary the "driver" that causes the gas to dissolve?
I generally use nitrogen at max 20% because it is manageable narcotically and from a density WOB point of view on deep dives, plus it means the helium is not so close to saturation as it would be if I used "norcotic trimix", so in principle I am less saturated with He.
Too much N2 means bends, narcs and high WOB.
Too much He means bigger risk of a He bend and the willies.
Adjust the proportions for optimum effect.

With me in principle? here comes the twist.
IF it were possible to use 10 different inert gases! (decamix?) each one at say 10%, none of the individual gases would exceed a pp over 1 bar at 90m and the "driver" which causes them to dissolve, would be substantially reduced, - maybe to a "no stop" saturation level !!!
IF this were possible could decompression be avoided altogether ?!?
Unfortunately there aren't enough inert gases with the appropriate properties for a diluent.
Quadmix maybe??
Gives yer brain a workout doesn't it?
Tim

__________________
Iechyd da

Simon Mitchell

Gidday Tim, long time no hear!!

Sorry to rain on your parade but applying your own excellent explanation of Dalton's law, you will appreciate that at the end of a dive with your ten gases, the total pressure of gas in a tissue will equal the sum of the partial pressures.

For a bubble to grow, the following condition must be satisfied:

Ptiss > Pamb + ((2 x surface tension) / bubble radius)

Where: Ptiss = total gas pressure in the tissue
Pamb = ambient pressure

Since Ptiss includes the sum of partial pressures of all inert gases in the tissue, it doesn't matter if you have created a situation where the partial pressures of the individual gases are low by breathing 10 gases. If you add them together and Ptiss satisfies the above condition then you are no further ahead.

Good to see you around here.

Warm regards,

Simon M

Underwaterbear

Hi Tim,
Interesting theory. You first


I'm, at heart, skeptical about the free lunch this idea suggests might be on offer and I have the feeling that there might be some cummulative effect on vapour pressure in tissues and hence your bubbles will just have 4 different inert gasses instead of the usual two. If this is not right maybe your idea has merit?

Cheers.
AB


Edit: Ahh, there you go...thanks Doc.

Tim Cashman

Hi Simon Howzitgoin?
(Read Keiths book Deep Water Gold? He did a good job of it. Your on pages 182 and 229!)

Re "Multimix"
I'm sure you're right or someone would have used this concept by now.
The concept is purely the physics of gases dissolving in liquids and what drives it.

Henry's Law was the twist.
Each component gas goes in or out of solution in proportion to the pp of itself vs the saturation of itself?
ie it goes in and out of solution independently of its neighbours?

I was theorising if there was an ideal balance of gases what could it be?

I take your point though, that if there is a 10 ata ambient and 10 gases all at pp of 1 bar you still get 10 bar total and what goes in must come out again.
10 bar in = 10 bar out later; irrespective of whether it is a multiple gas mix or a single gas.

Pub!

Tim

__________________
Iechyd da

Simon Mitchell

Mate!

The smartest thing I've read on any forum for ages!

Simon

jonas isaksen

Might be due to ignorance, however the transition from 8.4375Kgs/m3 to 58 meters is something in my theoretical education that has become lost. Is it possible to have the transition explained as well?

bendomatic

(1.429 * 21% * xata) + ( 1.250 * 79% * xata) =8.4375 kgs/m3
-> .3009*x ata + .9875* x ata = 8.4375
-> (.3009+ .9875) * x ata = 8.4375
-> 1.2884 * x ata= 8.4375
-> x ata = 8.4375/1.2884
-> x ata = 6.576
D(m)= (D(ata)*10)-10
-> x (m) = (6.576*10)-10
-> x (m) = ~56

i suspect some rounding errors to account for the difference.

"state of origin" rugby league here tonight so lots of piss being drunk
rachel

GO QUEENSLAND!

.....OR
This would have been easier to type and quicker to work out:
GIVEN (1.429 * 21% * 5ata) + ( 1.250 * 79% * 5ata) =6.438 kgs/m3
AND (1.429 * 21% * xata) + ( 1.250 * 79% * xata) =8.4375 kgs/m3
the equation becomes a ratio.
-> x ata= 8.4375/6.438 * 5 ata
-> x ata = 6.552
-> x m =~56m

__________________
why deal with idiots on the net when you have to spend all day dealing with them at work.