Background Acoustic Fields
The Background Acoustic Fields makes it possible to define a background field in a domain. This condition can be used to model scattering problems or as an inlet-like condition. In the latter case, when a perfectly matched layer is also present, you can set up a model with an incident field that also lets any reflected waves leave the computational domain. The feature is similar to the Background Pressure Field feature in Pressure Acoustics and the Background Acoustic Fields in Thermoviscous Acoustics.
This condition defines the background fields at the domain level (ρb, ub, pb). The total acoustic field is now the sum of the scattered field (the dependent variables solved for) and the background field, such that
On interior boundaries, continuity in the total field is automatically applied. All boundary conditions are expressed in terms if the total fields.
Background Acoustic Fields
Enter values or expressions for:
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Background acoustic density ρb (SI unit: kg/m3).
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Background acoustic velocity ub (SI unit: m/s).
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Background acoustic pressure pb (SI unit: Pa).
Several predefined variables exist for the total, background, and scattered field: the temperature, the entropy, the intensity, and the sound pressure level. They are located in the plot menu group Background and scattered fields, when postprocessing.