I prefer to prepare for the worst case scenario, so that when an incident finally happens, I have a backup plan, and a backup to that. This is really helpfull when things start to fail big time.
Scenario
Night time ice dive, clear silt-free water, wide sea, no reference points, safety line to surface, I'm diving alone as my buddy is at the surface keeping the safety line. My computers fail. The only usable reference is the safety line. It gives me direction but no speed indication, as the rope *floats* as it should.
Question
How do I control my ascent rate?
(yes, with a secondary computer, but let's assume they both failed or got lost)
Some initial thoughts
Air bubbles go up. Stokes formula says that the ascent rate of air bubbles in liquid is relative to the
- density difference between the liquid and air (pretty constant, even with air pressure changing tenfold)
- bubble radius squared
- bubble shape
So bigger bubbles go faster. As bubbles ascend, they also get bigger (due to pressure drop) and accelerate. I suspect that at some point the surface tension is too small and the bubbles break into smaller bubbles. Hence, bubbles should have a maximum speed, and also a minimum speed that depens on the size of the smallest bubbles (once they gain their initial speed).
Now how big are the smallest bubbles, and at what rate do they ascend when they pass my mask? And what is the maximum speed of air ascending freely through water?
Scenario
Night time ice dive, clear silt-free water, wide sea, no reference points, safety line to surface, I'm diving alone as my buddy is at the surface keeping the safety line. My computers fail. The only usable reference is the safety line. It gives me direction but no speed indication, as the rope *floats* as it should.
Question
How do I control my ascent rate?
(yes, with a secondary computer, but let's assume they both failed or got lost)
Some initial thoughts
Air bubbles go up. Stokes formula says that the ascent rate of air bubbles in liquid is relative to the
- density difference between the liquid and air (pretty constant, even with air pressure changing tenfold)
- bubble radius squared
- bubble shape
So bigger bubbles go faster. As bubbles ascend, they also get bigger (due to pressure drop) and accelerate. I suspect that at some point the surface tension is too small and the bubbles break into smaller bubbles. Hence, bubbles should have a maximum speed, and also a minimum speed that depens on the size of the smallest bubbles (once they gain their initial speed).
Now how big are the smallest bubbles, and at what rate do they ascend when they pass my mask? And what is the maximum speed of air ascending freely through water?
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