Transient Pressure Acoustics Model
The Transient Pressure Acoustics Model node adds the equations for primarily time-dependent (transient) acoustics modeling. This is the scalar wave equation
where pt is the total acoustic pressure, ρ is the fluid density, c is the speed of sound, qd is the Dipole Domain Source, and Qm is the Monopole Domain Source. In this formulation of the wave equation, the speed of sound and density may in general be space dependent but only slowly varying in time, that is, at a time scale much slower than the variations in the acoustic signal.
In the Settings window, define the properties for the acoustics model and model inputs including temperature.
Transient Pressure Acoustics Model
Select a Fluid model: Linear elastic (the default), Viscous, Thermally conducting, Thermally conducting or viscous, General dissipation, or Ideal Gas. Then see the descriptions for The Pressure Acoustics, Frequency Domain Interface:
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Linear Elastic Fluid Model
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Thermally Conducting and/or Viscous Fluid Model
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Ideal Gas Fluid Model
See Pressure Acoustics (frequency domain) for details of the fluid model equations. Nonlinear effects can be included using the Nonlinear Acoustics (Westervelt) node.
Model Inputs (Ideal Gas Only)
When Ideal gas is selected as the Fluid model, both the Temperature T and Absolute pressure pA fields are always enabled. Select, User defined (the default), Common model input, or an input from another physics interface, if applicable.
In addition, the Temperature T and Absolute pressure pA can be picked up from another physics interface where the fields have been calculated. For example, select a temperature field defined by a Heat Transfer interface or a Nonisothermal Flow interface (if any). Or, if applicable, select a pressure as defined by a Fluid Flow interface present in the model. For example, select Absolute pressure (spf) to use the absolute pressure defined by a Laminar Flow interface spf.
The Nonisothermal Flow interface requires the addition of the Heat Transfer Module or CFD Module.
Details about the Model Input and the Default Model Inputs are found in the Global and Local Definitions chapter of the COMSOL Multiphysics Reference Manual.