bubble ascent rate

[endoman]

I've heard the general guide, don't ascend faster than your bubbles, but at what rate do bubbles ascend?

[nigelH]

Originally Posted by endoman

I've heard the general guide, don't ascend faster than your bubbles, but at what rate do bubbles ascend?

If they are small enough they are virtually stalled so I suppose it depends how good your eyesight is.

Look at the really tiny ones in your beer some day.

[nickb]

Originally Posted by endoman

I've heard the general guide, don't ascend faster than your bubbles, but at what rate do bubbles ascend?

Depends how big they are. I learned 'don't ascend faster than a pea-sized bubble' when I was a BSAC novice back when dive computers cost a fortune and we dived with a watch and an analogue depth gauge which was accurate to about 3 meters.

[Twinsetmad]

Originally Posted by endoman

I've heard the general guide, don't ascend faster than your bubbles, but at what rate do bubbles ascend?

Its don't assend faster than the small bubbles.... bigger bubbles travel faster due to their bigger serface area.... so its a relative question ..? see....

[PW1664]

The relationship between the size of a bubble (air) traveling up in a liquid
(water)and the speed of the bubble is quite complicted.

Here are some of the factors that have to be taken into account [ in no particular order]:

1. The presence of surface active impurities, which accumulate at the
surface of the air/water interface and "lubricate" the rise of the bubble
increasing its speed.
These surface active impurities are not necessarily uniformly distributed at
the interface either. They tend to accumulate at the lower end of the rising
bubble.
2. The size of the bubble.
3. The viscosity of the continuous phase, in this case water.
4. The Reynold's number, Re, of the bubble: Re = (Dv)*(Ut)*(r)/(m), where:
Dv = [(6)*(V)/(pi)]^1/3 where V = volumetric rate of flow, and has
dimensions, m^3/sec. (Ut) = the terminal speed of the bubble, meters/sec.
(r) = density of the continuous phase (water). And (m) = viscosity of the
continuous phase. As the value of Re increases in various ranges, the shape
of the bubble will change from a sphere with no circulation, a sphere with
the air circulating due to drag at the air/water interface, and oblate
spheroid, to an irregular mushroom-shape.

And the equations of motion of the rise are solved numerically.

[gerbil]

er wot?

[frosty the snowman]

Originally Posted by PW1664

The relationship between the size of a bubble (air) traveling up in a liquid
(water)and the speed of the bubble is quite complicted.

Here are some of the factors that have to be taken into account [ in no particular order]:

1. The presence of surface active impurities, which accumulate at the
surface of the air/water interface and "lubricate" the rise of the bubble
increasing its speed.
These surface active impurities are not necessarily uniformly distributed at
the interface either. They tend to accumulate at the lower end of the rising
bubble.
2. The size of the bubble.
3. The viscosity of the continuous phase, in this case water.
4. The Reynold's number, Re, of the bubble: Re = (Dv)*(Ut)*(r)/(m), where:
Dv = [(6)*(V)/(pi)]^1/3 where V = volumetric rate of flow, and has
dimensions, m^3/sec. (Ut) = the terminal speed of the bubble, meters/sec.
(r) = density of the continuous phase (water). And (m) = viscosity of the
continuous phase. As the value of Re increases in various ranges, the shape
of the bubble will change from a sphere with no circulation, a sphere with
the air circulating due to drag at the air/water interface, and oblate
spheroid, to an irregular mushroom-shape.

And the equations of motion of the rise are solved numerically.

Paul, you ARE going to return to animating people farting and having sex soon aren't you?

[endoman]

So no one knows then

[gerbil]

I've just had to explain to my wife why i was staring intently at the bubbles in my beer

[PW1664]

Originally Posted by frosty the snowman

Paul, you ARE going to return to animating people farting and having sex soon aren't you?

Just trying to help