Hi,
I am modelling an alkaline water electrolyzer by using multiphase flow and species transport physics.
I am confused between gas and bubbles terms. From multiphase flow I can simulate the gas and liquid phase. While, with species transport I can simulate gas concentration in liquid and bubble nucleation.
Is bubble nucleation indirectly tells about gas region?
In two-phase gas-liquid media, one may define le void fraction (alpha) as the local ratio of the volume of gas (Vg) by the total volume (Vl+Vg) (alpha=Vg/(Vl+Vg)). When it comes to gas-liquid bubbly flows, the volume of the gas per unit of the total volume is thus the volume of all the bubbles within a total given volume. These can be defined locally by tending the total volume to infinitesimal value
The difference is in the morphology of the flow:
bubbly flow - gaseous and liquid phase are NOT mixed on a molecular level, but the gaseous phase forms bubbles as macroscopic inclusions into a continuous liquid phase. E.g. Air bubbles of 2mm size in water.
flow of a mixture - the gaseous and liquid phase are mixed on a molecular level. No macroscopic inclusions of either of the two phases can be observed. E.g. dissolved CO2 in water.
Bubble nucleation - the process of forming first macroscopic bubbles from a continuously dissolved gaseous phase. E.g. you open a pressurized bottle of mineral water with gas. In the first moment, there is only clear water visible. But after some miliseconds first bubbles appear and this process (e.g. if you shake the bottle) can become pretty "violent". This is called nucleation and bubble growth by depressurization. Other mechanisms of nucleation are possible.
Regards,
Dr. Th. Frank.
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