hi folks do anyone of you know how i need to set the boundarycondition on a face that so it function as a valve (only inlet, no outlet). it must fullfill a tank with air, if the presure in the tank is less than the atmospheric presure. thanks christian

after each time step, you can check using a UDF if the pressure in the tank is less than atm. pressure. If yes, then you can impose some velocity. Thus model the bc as vel. inlet. use define profile to set vel profile. depending on pressure values, the velocity is either zero (valve shut) or some positive value which will be decided from your valve characteristics.