Use the Thermoviscous Acoustics Model node to define the model inputs (the background equilibrium temperature and pressure) and the material properties of the fluid (equilibrium density, dynamic viscosity, bulk viscosity, thermal conductivity, and heat capacity at constant pressure) necessary to model the transient propagation of acoustic compressible waves in a thermoviscous acoustic context. Extended inputs are available for the coefficient of thermal expansion and the compressibility, which enables modeling of any constitutive relation for the fluid.

the equations are formulated in terms of the total acoustic fields pt, ut, and Tt. If the Background Acoustic Fields feature is added, for modeling scattering problems or as a source, the total fields are the sum of the background acoustic fields and the scattered acoustic fields. The equations can be extended to include nonlinear effects by adding the Nonlinear Thermoviscous Acoustics Contributions.

The Model Inputs, the Thermoviscous Acoustics Model, and the Thermal Expansion and Compressibility sections are the same as for the frequency domain interface. They are described under the Thermoviscous Acoustics Model section in The Thermoviscous Acoustics, Frequency Domain Interface.

Note that for the transient interface, it is equally important as for the frequency domain interface, to set the material parameters correctly. The values of the coefficient of thermal expansion and the isothermal compressibility are prone to errors, so make sure to take a thorough look at the Thermal Expansion and Compressibility section.