Loud BANG, lots of bubbles

[johndiver999]

Drug upward by the rising bubbles. I’ve never heard of that. If there was that much air in the water then the reduced buoyancy would make you sink?, I would guess.

I know from experience that any sort of sudden stress underwater causes me to want to breathe more deeply and also not to exhale quite as much. When stuff happens, I have to remind myself to really exhale and be vigilant against the natural propensity to rise.

Getting stressed by circling sharks on deco, is a perfect example of something that is both distracting and potentially stressful, and I when shallow, even a small movement from neutral can quickly cause a large change in depth. One reason why I prefer to hang in a negative condition from an smb while on a stop.

 

[tursiops]

Drug upward by the rising bubbles. I’ve never heard of that. If there was that much air in the water then the reduced buoyancy would make you sink?, I would guess.

Yeah, you'd think. But the whole buoyancy vs weight thing is a static concept, not dynamic. Imagine pushing something along the bottom by using an air hose....there is a lot of force in the turbulence/entrainment and air pressure...and while rising, the bubbles get bigger and thus go faster, too. Think of it as bubble-induced upwelling...it is the upward current that carries you up more than the loss of buoyancy takes you down.

Liquid Jet Pumped by Rising Gas Bubbles

From observations of a stream of gas bubbles rising through a liquid, a two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. The bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped...

asmedigitalcollection.asme.org

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Calculating the buoyant force of a rising bubble

I am solving the problem: A gas bubble rising from the ocean floor is 1 inch in diameter at a depth of 50 feet. Given that specific gravity of seawater is 1.03, the buoyant force in lbs being ex...

engineering.stackexchange.com

 

[crofrog]

When in the process did you shut down the valve?

 

[stretchthepenn]

Most likely you were going up NOT because of breathing hard but rather because you were dragged along by the rising bubble cloud. Something similar happened to my buddy recently at about 60 ft; he was on a single BM tank; he was venting his BCD as fast as he could when he started going up. I gave him my reg and tried to shut off his gas. Someone else was holding onto my fin. Even so, with me sort of on top of him pushing down, my fin being held, and him venting, we went to the surface in a bit over 20 seconds; my ascent rate on my computer showed 132 ft/min on the last 10s data point. We sucked on O2 at the surface. No ill effects.

Ah... That makes sense. I don't feel quite so bad about losing control of my buoyancy, then.

 

[stretchthepenn]

When in the process did you shut down the valve?

Pretty much last. I swapped regs, grabbed onto the buoy line, went feet-down and vented everything, and then turned off the valve.

Ideally, shutting down the leak would've been priority #1, but (a) the 2nd stage popped off after an exhale, so I had empty-feeling lungs and needed to breathe, and (b) I was rising fast. Had I gone for the valve first, I'd've corked.

 

[johndiver999]

Yeah, you'd think. But the whole buoyancy vs weight thing is a static concept, not dynamic. Imagine pushing something along the bottom by using an air hose....there is a lot of force in the turbulence/entrainment and air pressure...and while rising, the bubbles get bigger and thus go faster, too. Think of it as bubble-induced upwelling...it is the upward current that carries you up more than the loss of buoyancy takes you down.

Liquid Jet Pumped by Rising Gas Bubbles

From observations of a stream of gas bubbles rising through a liquid, a two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. The bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped...

asmedigitalcollection.asme.org

Cookie Absent

Calculating the buoyant force of a rising bubble

I am solving the problem: A gas bubble rising from the ocean floor is 1 inch in diameter at a depth of 50 feet. Given that specific gravity of seawater is 1.03, the buoyant force in lbs being ex...

engineering.stackexchange.com

On further thought... I do recall snorkeling above scuba divers when the water (and air) was uncomfortably warm. The rising bubbles and the entrained water WAS significantly cooler and was refreshing... definitely moving cooler water upward, but I also wonder if the adiabatic cooling of the bubbles cooled the water too?

 

[Jonn]

What a great practice! Not what you were planning but it was a ‘perfect failure’. You could have done better, that will always be true, but having this experience in a relatively safe environment made you a better diver than you were yesterday.

Why were you using such a rich mix though?! Safe enough at your shallow depth but wouldn’t regular air have served? Or was that just what you had in the tank?

 

[stretchthepenn]

What a great practice! Not what you were planning but it was a ‘perfect failure’. You could have done better, that will always be true, but having this experience in a relatively safe environment made you a better diver than you were yesterday.

Why were you using such a rich mix though?! Safe enough at your shallow depth but wouldn’t regular air have served? Or was that just what you had in the tank?

It was mostly a convenience thing. We both have multiple tanks of various nitrox mixes, but all our air tanks need viz inspections before we can get fills. Plus, all our nitrox tanks are already set up, and tearing down/resetting the rigging gets really tedious really fast.

 

[Graeme Fraser]

Yeah, you'd think. But the whole buoyancy vs weight thing is a static concept, not dynamic. Imagine pushing something along the bottom by using an air hose....there is a lot of force in the turbulence/entrainment and air pressure...and while rising, the bubbles get bigger and thus go faster, too. Think of it as bubble-induced upwelling...it is the upward current that carries you up more than the loss of buoyancy takes you down.

Liquid Jet Pumped by Rising Gas Bubbles

From observations of a stream of gas bubbles rising through a liquid, a two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. The bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped...

asmedigitalcollection.asme.org

Cookie Absent

Calculating the buoyant force of a rising bubble

I am solving the problem: A gas bubble rising from the ocean floor is 1 inch in diameter at a depth of 50 feet. Given that specific gravity of seawater is 1.03, the buoyant force in lbs being ex...

engineering.stackexchange.com

This makes sense. Basically the same concept as an air lift used to excavate in commercial diving. A very simple device comprising a large diameter open ended tube with an air inlet part way up. When compressed air is introduced and automatically vents upstream, the resulting draw creates a vacuum downstream. These can be very powerful and will easily lift anything in it's path, including wayward limbs if you're not careful.

Edit. Got my upstream and downstream mixed up.

 

[John C. Ratliff]

The 2nd stage was factory-tightened. I didn't futz with it before the dives. Afterward, I tightened both the new 2nd stages with wrenches and gave 'em a tiny little tug.

That needs to be reported to the factory!

SeaRat