Gravity on fluid cavity

[TimAero]

Currently I am working on a model for a hydrogen tank in Abaqus (Abaqus/CAE 2020). I would like to use the fluid cavity interaction to model the hydrogen. When I tried to apply gravity to the model, the fluid in the cavity is not taken into account to calculate the gravitational loads. Also I get a warning; 'In this type of analysis one would normally expect that a density for material fluidcavityprop would be defined'. I have however added a density to the FluidCavityProperties, I checked and it is present in the CAE, in the keyword editor and in the input file (Abaqus/CAE 2020). Where did I go wrong? I have attached a very simple shell-box model to show the issue. Please note that I have set the density of the box itself to 0 such that the presence of the weight of the fluid is abundantly clear in the results.
Thank you in advance.

 

[FEA way]

Apparently, fluid cavities are not taken into account for gravity loads. My tests also confirm that.

 

[TimAero]

Do you know an other way to model fluid/gas in a cavity under gravity load? I don't want to go into adaptive meshing with CPE4R elements or CEL techniques. since this is a bit of over kill to the problem at hand.

 

[FEA way]

You can still use the fluid cavity and just add the mass separately, e.g. with a nonstructural mass feature.