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When Compressible gas, adiabatic is selected, enter a Reference pressure pref (default 1 atm), the Reference temperature Tref (default 293.15 K), and the Ratio of specific heats γ (default 1.4). The gas temperature is computed and stored in a variable called <item>.T, where <item> is the feature path (for example solid.enc1.fl1).
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When Compressible fluid is selected, enter the Reference pressure pref (default 1 atm) and the Compressibility of fluid χf (default 4e-10 Pa-1). By entering a compressibility which is much smaller than the surrounding solid (for example, 1/(1e3*K)) where K a representative bulk modulus of the solid), the cavity will become nearly incompressible. Extremely low compressibility may lead to numerical problems.
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When User defined is selected, enter an expression a Pressure p. The default is an expression similar to (-2.5E9[Pa])*solid.enc1.DeltaV/solid.enc1.V_ref. The pressure is typically a function of the volume change. To apply a constant pressure load, use the Prescribed Pressure node instead.
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When Automatic is selected, the reference volume is equal to the volume during the initialization of the study step (spatial frame configuration). In particular, this is useful when the cavity is already deformed due to an initial overpressure applied in a previous study step.
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When From undeformed configuration is selected, the reference volume is equal to the volume of the undeformed configuration (material frame configuration).
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When From deformed configuration is selected, the reference volume is equal to the volume during the initialization of the study step (spatial frame configuration). In particular, this is useful when the cavity is already deformed due to an initial overpressure applied in a previous study step.
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When User defined is selected, enter an expression for the reference volume, Vref. The default is an expression similar to withsol('sol1',solid.enc1.V).
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When Automatic is selected, the method to compute the fluid pressure is automatically selected. This setting should be appropriate for most cases.
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When Pressure formulation is selected, the fluid pressure is computed with a global auxiliary DOF, which represents the fluid pressure.
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When Strain formulation is selected, the fluid pressure is computed with a global auxiliary degree of freedom (DOF), which represents the volume change.
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