In my problem i am considering one sump ..i am not incluing full sump..i am considering only some part ...i want to know what boundary conditions we can apply for top surface of the sump..i am considering only some part of sump and assuming that confined by walls..So for sides i am applying as WALLS...i am a bit confused abt top surface of the sump.. If am not specify any thing for that top surface meance ..it will take that surface as wall..so plz...reply me..

wat are u modeling exactly? are u modeling a tank filling problem or just wat do u want to study at ur primary goal? this would give a better idea to suggest a possible solution rather than inviting vague answers.

Regards