Exterior Field Calculation (for Transient Models)
The Exterior Field Calculation feature adds the equations necessary to postprocess the exterior field to the computational domain for open problems. The feature is the same as the Exterior Field Calculation in The Pressure Acoustics, Frequency Domain Interface. This feature will only generate variables and results that can be used in postprocessing when the results of a time-dependent simulation have been transformed to the frequency domain using a Time to Frequency FFT study.
For more detailed information about the FFT study see the Time to Frequency FFT section in the COMSOL Multiphysics Reference Guide.
The feature only operates on the scattered field variables and is thus especially well suited for analyzing the results of a scattering problem. Such a model can be set up by using the Background Pressure Field (for Transient Models) feature combined with a radiation condition or PMLs. In this way radiation pattern of, for example, a loudspeaker modeled in the time can still be analyzed when an FFT of the time domain solution is performed.