How to defient the B.C at the Diaphragm
 

Hi, I have a problem with the B.C set up. I have a diaphragm that seperates the high pressure region and low pressure region. After the high pressure reaches some critical value, the diaphragm breaks. How to define the B.C on the diaphragm?

I want to define the diaphragm as wall condition before reaching the critical pressure, and let the wall condition at diaphragm disappear after the diaphragm breaks. How to set up this B.C?

Any help is appreciated.

Bob