Scott Riemer
Contributor
Does water temp have an effect on bouyancy? If so, how much?
Water temp and Bouyancy
- Thread starter Scott Riemer
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H2Andy
Contributor
good question
(i.e. "i never thougth to ask that before")
(i.e. "i never thougth to ask that before")
startag
Registered
most substances get denser as temperature decreases... but since water forms a lattice structure when it freezes, it actually is less dense(thus it floats in liquid water) but im really not sure how temperature effects water as it cools before it freezes.
Chris Walrod
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startag:
Good question Scott. I do know the surface tension of a liquid generally increases as the temperature decreases..
Not much help, I know..
rcohn
Guest
Here is a calculator for seawater density. http://www.es.flinders.edu.au/~mattom/Utilities/density.html I can't vouch for the accuracy. If you know the weight of yourself and all your gear, you can compute the volume of water you displace if neutrally buoyant. Then you can compute the change with temperature.
Ralph
Ralph
Temperature In Degrees Fahrenheit
Density per ft3 (lbs)
At 32 degrees or freezing point at sea level 62.418
At 39.2 degrees or point of maximum density 62.427
At 62.0 degrees or standard temperature 62.355
At 212 degrees or boiling point at sea level 59.830
Not sure how valid the data is http://energyconcepts.tripod.com/energyconcepts/water.htm but ut is consistant with other sources I found on the Internet.
Now take an example of a 5ft3 person and look at the buoyant fources applied at a few different temperatures (it is the principle that counts).
39.2F---> 62.427lbs/ft3 x 5ft3= 312.14lbs
62.0F---> 62.355lbs/ft3 x 5ft3= 311.78lbs
These results are the buoyant forces applied to an object (diver in this case) that is 5ft3. So the difference going form ~40F water to ~62F water would be about .37lbs.
Given that this would be a rather large diver and that an extreme temperature shift you could say it is relativly insignificant.
Now take this to the next step and apply how this could in any way effect a diver. Given that the 62F water will be at the surface and the 39F water at the bottom and you are probably wearing a thick wet suit (in anticapation of the COLD water). As you go down the wet suit will compress and as a result you will displace a smaller volume of water. The fact that the water will be more dense will actually assist you in this case. Note that the suit compressing will have an overwhelming effect on your buoyancy but the density will play a very small role. Also note that all these calculations are based on fresh water.
As always I reserve the right to be totally out to lunch and if so please let me knw as I am sure you all will
Density per ft3 (lbs)
At 32 degrees or freezing point at sea level 62.418
At 39.2 degrees or point of maximum density 62.427
At 62.0 degrees or standard temperature 62.355
At 212 degrees or boiling point at sea level 59.830
Not sure how valid the data is http://energyconcepts.tripod.com/energyconcepts/water.htm but ut is consistant with other sources I found on the Internet.
Now take an example of a 5ft3 person and look at the buoyant fources applied at a few different temperatures (it is the principle that counts).
39.2F---> 62.427lbs/ft3 x 5ft3= 312.14lbs
62.0F---> 62.355lbs/ft3 x 5ft3= 311.78lbs
These results are the buoyant forces applied to an object (diver in this case) that is 5ft3. So the difference going form ~40F water to ~62F water would be about .37lbs.
Given that this would be a rather large diver and that an extreme temperature shift you could say it is relativly insignificant.
Now take this to the next step and apply how this could in any way effect a diver. Given that the 62F water will be at the surface and the 39F water at the bottom and you are probably wearing a thick wet suit (in anticapation of the COLD water). As you go down the wet suit will compress and as a result you will displace a smaller volume of water. The fact that the water will be more dense will actually assist you in this case. Note that the suit compressing will have an overwhelming effect on your buoyancy but the density will play a very small role. Also note that all these calculations are based on fresh water.
As always I reserve the right to be totally out to lunch and if so please let me knw as I am sure you all will
Don Burke
Contributor
Yes,Scott Riemer:
There is a minor change in the density of water and that change also happens to the water in your body, so that portion is pretty much jump ball.
The big change is in the air in your BC. The idea gas law kicks in there and the bigger the bubble, the more the buoyancy changes.
Add that to the arguments against overweighting.
Yes... water temp changes buoyancy big time in several ways.
First, the colder the water the more exposure protection you need an consequently you are much more buoyant.
Secondly, in colder water you will probably be breathing faster and with greater tidal volume so that will add to your buoyancy as well.
Hope this helps.
BTW... the slight difference in buoyancy due soley to the change in density with different water temperatures is of no consequence.
First, the colder the water the more exposure protection you need an consequently you are much more buoyant.
Secondly, in colder water you will probably be breathing faster and with greater tidal volume so that will add to your buoyancy as well.
Hope this helps.
BTW... the slight difference in buoyancy due soley to the change in density with different water temperatures is of no consequence.
Actually I think the big difference is the warmer water can absorb more salt so the sea water actually is denser due to the salt content in warmer climates.
cheers,
cheers,
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