# Finding out compressibility of a fluid when bubbles are present?

1. Apr 12, 2013

### bzz77

I want to know approximately how compressible a fluid can become when H2O bubbles are present. Does anyone know how to do this? Thanks.

2. Apr 12, 2013

### Bobbywhy

Will you please explain what are "H2O bubbles"? Thank you.

Bobbywhy

3. Apr 12, 2013

### bzz77

I mean that if we have liquid and know its compressibility (it is approximately incompressible), then we add some gas bubbles to it (of known composition, let's assume H2O), then how can we calculate the mixture compressibility?

Is this a matter of looking up tabulated values for the gas compressibility at the temperature and pressure of interest, then summing the liquid and gas compressibilities, taking their mass fractions into account?

4. Apr 12, 2013

### Bobbywhy

H2O (water) does not form gaseous bubbles unless raised above its boiling point. Are you thinking of some other gas bubbles in water?

Compressibility is the fractional change in volume per unit increase in pressure. It seems reasonable to expect that if gas bubbles are added, then the volume would decrease more under the same pressure because gas is far more compressible.

There are not “look-up tables” for such mixtures. I think your only option would be to perform the experiment and measure the compressibility of the mixture.

Bobbywhy

5. Apr 12, 2013

### bzz77

Thanks, Bobby. I'm thinking of a liquid that is not water, but that is essentially incompressible. it would be at temperatures high enough that water gas would be stable. I want to do some flow calculations and I'd like to get a rough idea of how compressible the liquid plus gas mixture would be compared to liquid only.

I was hoping there might be a rough way to calculate this, but it appears not. Anyway, thanks a lot.

6. Apr 12, 2013

### Bobbywhy

bzz77, There may be work already done in the area you are interested in. See this patent, for instance:

"Method and apparatus for the determination of non-dissolved gas in liquids
ABSTRACT
The method enabling the quick determination of non-dissolved or free gas in a liquid sample. Involves measuring the density of a liquid sample in a closed vessel, subjecting this sample to a reduced pressure and thereby expanding the "free" gas in the liquid sample. After this expansion has taken place, but before allowing dissolved gas to come out of solution, the volume is fixed and a second density measurement is taken."