Thermoviscous Acoustic-Structure Boundary
The Thermoviscous Acoustic-Structure Boundary coupling () is used to couple a Thermoviscous Acoustics interface to any structural component. The feature couples to Solid Mechanics, Shell, Layered Shell, Membrane, and Multibody Dynamics interfaces.
The coupling prescribes continuity in the displacement field
where ut,fluid is the total fluid velocity (including a background component if applicable) and usolid is the solid displacement. The first equation is in the frequency domain and the second in the time domain, respectively. This coupling results in the stress also being continuous across the boundary. The condition for the total temperature Tt can be set to either isothermal or adiabatic. In the case where a shell or membrane is interior to the thermoviscous acoustics domain, a slit is automatically applied to the pressure p and temperature T degrees of freedom (DOFs).
The coupling has a special formulation for eigenfrequency studies, which allows the program to find the eigenvalue for coupled systems.
For an example using this multiphysics coupling see the Vibrating Micromirror with Viscous and Thermal Damping model: Application Library path Acoustics_Module/Vibrations_and_FSI/vibrating_micromirror
Settings
See Settings for further details about Label and Name.
The default Name (for the first multiphysics coupling feature in the model) is tsb1.
Coupled Interfaces
This section defines the physics involved in the multiphysics coupling. The Thermoviscous Acoustics and Structure lists include all applicable physics interfaces. See the Coupled Interfaces in Acoustic-Structure Boundary for details.
Thermal
Select the Thermal condition that applies on the solid surface to be either Isothermal (the default selected) or Adiabatic.
Constraint Settings
These settings are shown when the Advanced Physics Options is selected. It controls how the constraints (continuity in displacement and the thermal condition) are handled. For the Mechanical constraints type, select either Study controlled (the default), Weak constraints, or Pointwise constraints. For the Thermal constraint type, select either Pointwise constraint (the default) or Weak constraints. Finally, select the Constraint method to apply to the pointwise constraints, either Elemental or Nodal (the default).
When the Mechanical constraints type is set to Study controlled, the weak constraints are automatically selected when an eigenfrequency study is performed. This type of coupling is necessary as the eigenvalue (the angular frequency ω) enters the coupling expression. This will create extra variables at the boundary (so-called Lagrange multipliers), ensuring the correct behavior and solution. For a normal frequency domain study, the pointwise constraint is automatically selected. In the time domain there are no options, and the weak formulation is always used.