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2021 International Year of Caves and Karst: BCRA online seminars

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JoshW:

--- Quote from: mikem on March 11, 2021, 03:28:33 pm ---You would only want a constant buoyancy in a vadose system, for phreatic you would want it to be stay in the flow rather than rise to the roof.


--- End quote ---

by constant buoyancy I mean constant neutral buoyancy i.e. neither positively or negatively buoyant, but just hovers in place in still water, but follows the flows/currents

ChrisJC:

--- Quote from: JoshW on March 11, 2021, 03:32:51 pm ---
by constant buoyancy I mean constant neutral buoyancy i.e. neither positively or negatively buoyant, but just hovers in place in still water, but follows the flows/currents

--- End quote ---

Agreed. A smidge of positive buoyancy would be required I think to prevent it getting stuck at the bottom.

I think that because water is not compressible, then the density of water must be constant irrespective of depth, therefore a rigid object would have constant buoyancy regardless of depth. This means we could determine the buoyancy in a bucket of water and be confident that it would remain like that throughout the system.

Chris.

mikem:
You have approx 1 atmosphere more in pressure for every 10m deeper you go, so there is a slight increase, plus any flow creates turbulence, which will be particularly effective if it's dragging air down from the surface (that will reduce buoyancy). However, temperature has a much greater effect on the density than pressure.

JoW:
An interesting thread of conversation! For those that missed John's talk there will be another showing of it at some future date, but this hasn't been scheduled yet - watch this space along with our Facebook page and website for more details.

And a reminder that our next talk in the series is on Monday (12th April) at 7pm. This time we will be hearing Andy Farrant talk about chalk caves :)

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