Defining an Acoustic Medium
The equilibrium equation for small motions of a compressible, inviscid fluid flowing through a resisting matrix material is taken to be
The constitutive behavior of the fluid is assumed to be inviscid and compressible, so that the bulk modulus of an acoustic medium relates the dynamic pressure in the medium to the volumetric strain by
The bulk modulus Kf can be defined as a function of temperature and field variables but does not vary in value during an implicit dynamic analysis using the subspace projection method (Implicit Dynamic Analysis Using Direct Integration) or a direct-solution steady-state dynamic analysis (Direct-Solution Steady-State Dynamic Analysis); for these procedures the value of the bulk modulus at the beginning of the step is used.
Input File Usage
Use both of the following options to define an acoustic medium:
ACOUSTIC MEDIUM, BULK MODULUS DENSITY
Abaqus/CAE Usage
Property module: material editor: Bulk Modulus: