The Thermoviscous Acoustic–Thermoelasticity Interaction Multiphysics Interfaces
These two multiphysics interfaces require the MEMS Module license. For theory and physics interface feature descriptions relating to the Thermoelasticity multiphysics interface, see the Structural Mechanics Module User’s Guide.
The Thermoviscous Acoustic–Thermoelasticity Interaction, Frequency Domain () and the Thermoviscous Acoustic–Thermoelasticity Interaction, Transient () multiphysics interfaces, found under the Acoustics>Thermoviscous Acoustics branch () when adding a physics interface, combines the Thermoviscous Acoustics, Frequency Domain or Transient interface with the Thermoelasticity multiphysics interface. The physics interface solves for and has predefined multiphysics couplings between the displacement and temperature field in the solid and the acoustic variations in pressure, velocity, and temperature in the fluid domain.
It can be used, for example, for modeling the vibrating response of MEMS devices including detailed description of the damping. The physics interface is available for 3D, 2D, and 2D axisymmetric geometries.
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In the frequency domain, the physics interface solves the equations using a frequency-domain perturbation approach assuming all fields and sources to be harmonic. The displacement and temperature field in the solid are linearized around a stationary solution. Linear acoustics is assumed.
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In the time domain, the physics interface solves the equations in the time domain by coupling the deviation from reference in the solid to the acoustic fields in the fluid.
Prestressed Micromirror Vibrations: Thermoviscous–Thermoelasticity Coupling. Application Library path Acoustics_Module/Vibrations_and_FSI/micromirror_prestressed_vibration
The multiphysics interface combines The Thermoviscous Acoustics, Frequency Domain Interface or The Thermoviscous Acoustics, Transient Interface with The Thermoelasticity Interface, using the Thermoviscous Acoustic–Thermoelasticity Boundary multiphysics coupling.
Frequency Domain
When solving the multiphysics problem in the frequency domain it is necessary to use a frequency-domain perturbation approach. The reason is that the Heat Transfer in Solids physics (and Solid mechanics) is formulated in total fields, whereas the acoustic physics are formulated in perturbation variables. To solve the model two approaches exist:
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First solve a Stationary study step followed by the Frequency-Domain Perturbation study step. In the stationary step solve for the background temperature field in the solid (and potentially also the displacement). This solution is then taken as the linearization point for the frequency-domain perturbation problem.
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If the background temperature in the solid can be assumed constant, it is possible to only use the Frequency-Domain Perturbation step. In this case change the Value of linearization point to User controlled, the linearization point will be taken from the Initial Values node in the heat transfer physics interface.
Time Domain
In the time domain the situation is a bit different. Since the heat transfer interface solves for the total fields, the perturbation temperature is defined as the difference between the temperature solved for T and the reference temperature ht.Tref. The reference temperature is defined at the physics interface level in the Physical Model section. This value is typically a constant, but the value can be taken from a previously solved stationary problem. In that case, the reference value should also be used as the initial value for the transient simulation.