Hello,

Im trying to simulate a compressible gas inside a cube (0,1*0,1*0,1 m³) with a top plate attached to a spring (C=1 N/m) and Im using the following APDL commands:

when i supress the D command and apply a 100 N force to the top plate the displacement is accurate to the stiffness of an air suspension, which is proportional to the reference pressure (500000 Pa):

but when i unsupress the D command and i apply a force of 101 N, the fluid is no longer modelled and my top plate is holded only by the spring:

is it possible to simulate a fluid with a given internal pressure + an external force? or there are some limitations to 242 elements?

how come i can use the D command but not the IC command to initate the internal pressure? (is this the reason why my model doesnt work?)