Hellow~I have a container with liquid water and solid electrodes in it. The water will be absorbed by electrodes and the H2 is released from electrodes. So the water will be decreased and the H2 will move out off the container. So the waterface ( boundary ) must drop down (Because it need to obey the mass conservation).

Can sombody tell me how to do it ?

Air should occupy the position of water as water level drops down. You need to use VOF model to see changes in water level.

I have two problem.

(1) If I establish the air and water mesh, how can I define the face between air and water.(It should be contained the water temperature convected by air and the generated H2 or O2 can go through this water face to air )

(2) If I open the VOF, how do I define the two gas(H2 andO2) in the water.There are three phaeses.(liquid-water, H2-gas and O2-gas).

This problem bothered me very long time. Thank you.