I patched the fluid domain with 1400 gauge pressure and set up the boundary condition at the outlet to be 0 gauge pressure. But I am getting floating point exception. What am i missing?
I think you are missing the fact that the water is incompressible and the continuity must be fulfilled. Starting from a fully filled tank, the water level in the tank will diminish and the tank will be filled by increasing volume of air and diminisching volum of water. Have you modelled both air and liquid phases?
...and it seems, that the hydrostatic pressure in the tank is not taken into account as well. If the tank has no opening at all (besides the outlet, where we do not know from the post, where that outlet is located and how it is constructed), than how the replacing air should enter into the tank? Through which opening? If the CFD model is not providing any means for the replacing air to enter into the tank, than consequently no leakage of water can occur due to continuity.
I may add, that the leakage can be modeled as sort of an open tap with a specified flow rate function. This could depend on pressure, head, opening size, temperature, position. The continuity equation could consider water only as an unsteady incompressible flow.
It is a two-phase flow simulation(water,air). I need to model the sagging of a deformable container which is inside the water initially. I need to transfer the pressure as imported load to the Ansys-Structural from this fluent simulation, when the water drains and air fills up. But when i use 2phase model, i couldn't import pressure load. Is there any alternative way to model this scenario???