HI all

According to the help files "A fluid cavity structure is typically subjected to an external load , while the fluid inside the structure exerts internal pressure. Both the external load and the internal pressure dictate the structure's response (that is, its deformation), which creates a feedback loop for the external load and internal pressure to deform the structure further. The app provides the analysis coupling required to simulate cases in which you assume the cavity is filled completely by a fluid with uniform properties and state—it calculates the deformation of the structure and the pressure exerted by the fluid on the boundary surface." 

This is my understanding but this does not happen. As the external pressure increase, the cavity volume decreases and the cavity pressure is supposed to increase. This does not happen. Additionally, is gravity required? How is hydrostatic pressure accounted for if not? 

An example of a fluid cavity setup doing what is supposed to would greatly be appreciated. If this is not possible what is an alternative approach? If someone could point me to some documentation that would be helpful as well.

Thanks!