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how fast will bubbles rise in water?
    #5780757 -

What im wondering if there is a set speed that air will rise in a column of water.

this is for a project for creating an co2 injected algae growing system.

at one point in the system there will be a vertical column where heated (room temp) co2 gas will be injected constantly in small bubbles.

now i want the gas to be in contact with the water for as long as possible. I would like to have a downward flow of water slowing the raise of the bubbles of CO2.

but is this possible and is there an equation for calculating the sppeed of the raise of the bubbles against a set current.


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PEACE

:mushroom2:zippoz:mushroom2:



"in times of widespread chaos and confusion, it has been the duty of more advanced human beings - artists, scientists, clowns, and philosophers - to create order. In such times as ours however, when there is too much order, too much m management, too much programming and control, it becomes the duty of superior men and women and women to fling their favorite monkey wrenches into the machinery. To relieve the repression of the human spirit, they must sow doubt and disruption"

"People do it every day, they talk to themselves ... they see themselves as they'd like to be, they don't have the courage you have, to just run with it."

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Re: how fast will bubbles rise in water? [Re: ZippoZ]
    #5781239 -

You should consult with an engineer.


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ca'rouse (k-rouz)
intr.v.
To engage in boisterous, drunken merrymaking.

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Re: how fast will bubbles rise in water? [Re: ZippoZ]
    #5782641 -

Sounds like that would be a fluid-dynamics question, which means it's also a hard question


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I find your lack of faith disturbing

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Re: how fast will bubbles rise in water? [Re: ZippoZ]
    #5782790 -

Sounds like this:

http://www.iop.org/EJ/article/1742-5468/2006/01/P01009/jstat6_01_p01009.html

and especially this article, would be of interest to you:

http://scitation.aip.org/getabs/servlet/...cvips&gifs=yes.

:grin:

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Re: how fast will bubbles rise in water? [Re: ZippoZ]
    #5788641 -

why does it matter though?

just do the best you can to keep the gas in the water :shrug:
you can install a spirle inside the container for the gas to keep from going straight up and of course inject the gas as finely as you can (making very small bubbles... maybe with very small holes and high pressure or using some sort of osmotic type system would work better?)


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:mushdance::sanpedro::peyote::mushroom2: :heart: Shr:supershroom::supershroom:mery :heart: :mushroom2::peyote::sanpedro::mushdance:
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Re: how fast will bubbles rise in water? [Re: ZippoZ]
    #5788833 -

ok, that is fluid dynamics, it's not a real complicated problem

the rate that a bubble rises depends on VISCOSITY, DENSITY and PARTICLE SIZE, this is all very generalize, the situation is the same if your particle is an air bubble or styrafoam packing peanuts or billiard balls. Adding the flow of water should be additive with whatever pressure driven flow of bubbles (or in your case "subtractive")

Viscosity is the resistance to changing the flow of a fluid. Maple syrup is more viscous than water, bubbles rise slower. For water, temperature and solute concentration doesn't have have much of an effect, unless you're adding something like syrup or glycerine.

Density is the amount of weight for a standardize volume of material. Density matters for both the liquid and the particle. Density controls the influence of gravity on the material, pressure. In a high density fluid, a low density particle will rise. This one is easy and intuitive, known as pressure driven flow or differential flow. Again, changes in temperature and changes in the solution make very little difference in the density of water.

Theoretically, particle size doesn't matter, but in reality it can make a difference, only in extreme cases. For water and air, size isn't an issue. There are some fancy materials with interesting viscosity performance. Water is an ideal fluid, silly-putty is a non-ideal fluid.

So, in conclusion, fluid dynamics can get very complicated, but limiting your system to water and air simplifies the problem a lot. You could calculate the flow rates, but for you, the rate bubbles rise will be nearly constant in water. Get out a ruler and stop watch if you want to test it. You will be able to adjust the rate by adding flow of water in the opposite direction.

edit: I read those papers, decent. I've taken all sorts of engineering courses, mostly soft materials stuff.

edit #2: I also realized that this is also a continuum theory or math theory question. It's a matter of perspective and coordinate system.

If you're inside the bubble or particle or maybe you're the particle, then the flow of yourself through water would appear independent of the water flow.

If you're outside the bubble/particle/water, then the flow of the bubbles would appear to depend on the water flow.

Edited by Nashbar (06/25/06 08:42 AM)

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Re: how fast will bubbles rise in water? [Re: ZippoZ]
    #5788935 -

i would say get a 1.3 meter tube and mark a meter off in the middle skewed towords the top. get a stop watch and time bubbles from mark to mark.

Nashbar, in real life the size of bubbles does change their rate of speed in water because of the weigth and therefore pressure of the water. if you dont believe me, go scuba diving and relase a really large buggle and a tiny bubble.


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No, no, you're not thinking, you're just being logical. ~ Niels Bohr

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Re: how fast will bubbles rise in water? [Re: automan]
    #5789399 -

actually, I don't think so, particle size in water doesn't matter because it is an ideal fluid (newtonian, linear viscoelasticity), but again this is relative, and nothing is really ideal. When the particle size becomes large enough relativistically, compared to the size of water molecule interactions, then the bubble no longer acts as a purely dispersed phase.

There are a lot of complexity that can be added, I could get into the shear response of fluids, but it's mostly pointless for water. If you're bubbling through antifreeze, it's another story.

One could make an argument that particle size effects INTERNAL pressure due to the radius of curvature of the bubble, but again, this is relativity, and for two ideal fluids in gravity, the capillary force is negligible.

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Re: how fast will bubbles rise in water? [Re: Nashbar]
    #5789411 -

i'm not sure about the theory behind it, but i do have much real world experience. i have been a certified scuba diver for close to 17 years. if you go out into open water and release some air, big and small bubbles will form and start to move towards the surface. big bubbles trvel there faster than small bubbles.


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No, no, you're not thinking, you're just being logical. ~ Niels Bohr

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Re: how fast will bubbles rise in water? [Re: automan]
    #5789428 -

are the big bubbles spherical? or tear-drop or umbrella shaped?

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Re: how fast will bubbles rise in water? [Re: Nashbar]
    #5789441 -

a big bubble starts as round, then opens up to an umbrella as it rises gaining volume do to the decreasing pressure. then it opens up into a ring and breaks up into smaller bubbles that grow with the decrease of pressure and repeats the cycle.


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No, no, you're not thinking, you're just being logical. ~ Niels Bohr

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Re: how fast will bubbles rise in water? [Re: automan]
    #5789792 -

this is totally aside

the point that bubbles are no longer spherical is at the strain rate where water is no longer linearly viscoelastic. At this point, cohesive failure (cavitation) occurs in water, this energy dissipation would then allow bubbles to flow faster.

The scuba diving bubbles are an extreme case, see above. Gas decompressing and increasing in volume adds another bit of complexity.

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Re: how fast will bubbles rise in water? [Re: Nashbar]
    #5790477 -

"Particle" size in water does matter when your "particles" are macroscopic bubbles. For spherical bubbles, there are mainly 2 forces acting---buoyancy and drag. Buoyancy increases with bubble size while drag also increases. Which of these forces is greater (there is no a priori reason to believe they're equal) determines whether smaller or larger bubbles rise faster.

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Re: how fast will bubbles rise in water? [Re: Nashbar]
    #5791586 -

>actually, I don't think so, particle size in water doesn't matter

It matters a lot.

To determine the speed of a particle in fluid, you equal the resistance and the buoyancy forces.

Into the resistance the relative velocity of the particle in fluid goes with ^2
This way, the velocity is a function of the square root of the particle diameter among other things.


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Grow Mushrooms from Spores - PF-Tek for Simple Minds

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Re: how fast will bubbles rise in water? [Re: Anno]
    #5795142 -

well as there will be a variable amount of particles in the water, as im growing them in there, along with the consideration that what i was building needed to be more mobile...

i went on to a new design that does not take into consideration the speed of bubbles rising in a moving column of water. :smile:

although im pretty fascinated with the info in here, and will put it to good use :smile:


--------------------
PEACE

:mushroom2:zippoz:mushroom2:



"in times of widespread chaos and confusion, it has been the duty of more advanced human beings - artists, scientists, clowns, and philosophers - to create order. In such times as ours however, when there is too much order, too much m management, too much programming and control, it becomes the duty of superior men and women and women to fling their favorite monkey wrenches into the machinery. To relieve the repression of the human spirit, they must sow doubt and disruption"

"People do it every day, they talk to themselves ... they see themselves as they'd like to be, they don't have the courage you have, to just run with it."

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Re: how fast will bubbles rise in water? [Re: ZippoZ]
    #5795433 -

zippoz, why dont you call MIT and ask to tour their setup. they started this experiment a few years back.


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No, no, you're not thinking, you're just being logical. ~ Niels Bohr

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Re: how fast will bubbles rise in water? [Re: automan]
    #5796812 -

its all funded by private industry or so i have been told by the guy over at unh funding the mit expierement...


--------------------
PEACE

:mushroom2:zippoz:mushroom2:



"in times of widespread chaos and confusion, it has been the duty of more advanced human beings - artists, scientists, clowns, and philosophers - to create order. In such times as ours however, when there is too much order, too much m management, too much programming and control, it becomes the duty of superior men and women and women to fling their favorite monkey wrenches into the machinery. To relieve the repression of the human spirit, they must sow doubt and disruption"

"People do it every day, they talk to themselves ... they see themselves as they'd like to be, they don't have the courage you have, to just run with it."

Extras: Filter Print Post Top
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