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 the input file (without node and element numbers for shortness) of 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.
*Heading
** Job name: TestFluidGravity Model name: Model-1
** Generated by: Abaqus/CAE 2020
*Preprint, echo=NO, model=NO, history=NO, contact=NO
**
** PARTS
**
*Part, name=Part-1
*Node
*Element, type=S4R
*Nset, nset=_PickedSet3, internal, generate
1, 602, 1
*Elset, elset=_PickedSet3, internal, generate
1, 600, 1
*Elset, elset=_FluidCavitySurface_SNEG, internal, generate
1, 600, 1
*Surface, type=ELEMENT, name=FluidCavitySurface
_FluidCavitySurface_SNEG, SNEG
** Section: Dummy
*Shell Section, elset=_PickedSet3, material=Dummy
1., 5
*End Part
**
**
** ASSEMBLY
**
*Assembly, name=Assembly
**
*Instance, name=Part-1-1, part=Part-1
*End Instance
**
*Node
1, 0., 0., 10.
*Nset, nset=_PickedSet5, internal
1,
*Nset, nset=_PickedSet6, internal, instance=Part-1-1
6,
*End Assembly
**
** MATERIALS
**
*Material, name=Dummy
*Density
0.,
*Elastic
69000., 0.33
**
** INTERACTION PROPERTIES
**
*Fluid Behavior, name=FluidCavityPriop
*Fluid Density
2.8898459
**
** BOUNDARY CONDITIONS
**
** Name: BC-1 Type: Symmetry/Antisymmetry/Encastre
*Boundary
_PickedSet6, ENCASTRE
**
** INTERACTIONS
**
** Interaction: FluidCavity
*Fluid Cavity, name=FluidCavity, behavior=FluidCavityPriop, refnode=_PickedSet5, surface=Part-1-1.FluidCavitySurface
** ----------------------------------------------------------------
**
** STEP: z-G
**
*Step, name=z-G, nlgeom=YES
*Static
1., 1., 1e-05, 1.
**
** LOADS
**
** Name: G-load Type: Gravity
*Dload
, GRAV, 9806.65, 0., 0., 1.
**
** OUTPUT REQUESTS
**
*Restart, write, frequency=0
**
** FIELD OUTPUT: F-Output-1
**
*Output, field, variable=PRESELECT
**
** HISTORY OUTPUT: H-Output-1
**
*Output, history, variable=PRESELECT
*End Step
** ----------------------------------------------------------------
**
** STEP: x-G
**
*Step, name=x-G, nlgeom=YES
*Static
1., 1., 1e-05, 1.
**
** LOADS
**
** Name: G-load Type: Gravity
*Dload
, GRAV, 9806.65, 1., 0., 0.
**
** OUTPUT REQUESTS
**
*Restart, write, frequency=0
**
** FIELD OUTPUT: F-Output-1
**
*Output, field, variable=PRESELECT
**
** HISTORY OUTPUT: H-Output-1
**
*Output, history, variable=PRESELECT
*End Step
** ----------------------------------------------------------------
**
** STEP: xz-G
**
*Step, name=xz-G, nlgeom=YES
*Static
1., 1., 1e-05, 1.
**
** LOADS
**
** Name: G-load Type: Gravity
*Dload
, GRAV, 13868.7, 0.707107, 0., 0.707107
**
** OUTPUT REQUESTS
**
*Restart, write, frequency=0
**
** FIELD OUTPUT: F-Output-1
**
*Output, field
*Node Output
CF, RF, U
*Element Output, directions=YES
LE, P, PE, PEEQ, PEMAG, S
*Contact Output
CDISP, CSTRESS
**
** HISTORY OUTPUT: H-Output-1
**
*Output, history, variable=PRESELECT
*End Step
I checked inputs and created a simple model to validate gravity on fluid cavity