Dear all. To simplify, here is the question raise: I have a volume of water inclosed in a fixed volume of steel. There is only water in this volume. Therefore, how will Starcd take into account the buoyancy of the water? If I put the buoyancy on, then when warmed up, the water will expand, but mathematically speaking, this expansion is not possible as the volume is fixed by the steel-walls. Does StarCd integrate some elasticity for the walls? I am afraid not...so shouldn't the results be wrong? Laure

What is the expansion coefficient of water?

It will not expand, instead you will have a high pressure raise.

Precise your problem.

My expansion coefficient is 0.0003914 (Beta). My problem is that with starCD, I can't model the interface between air and water, so I had to enclose the water in steel to model my problem. However, that leads to the physical probelem I explained earlier. So the pressure of the water will rise like crasy wich would not be the case in real life, as the steel would deform sufficiently to compensate that.(I have a thin steel layer).

You can model interfaces between water and air, with free surfaces (tutorial 15, StarCD 3.24), but only with constant density, and this is not your case. The pressure in your steel box is strongly dependent from the ratio between water and air. Sorry it seems, your current model is far away from the reality. StarCD can not stress analysis.