Physics-Controlled Mesh for Pressure Acoustics
When modeling acoustic problems using the Pressure Acoustics, Frequency Domain or the Pressure Acoustics, Transient interfaces the computational mesh can be automatically set up using the Physics-controlled mesh functionality. For these two physics, the generated computational mesh will follow best practices. The mesh will automatically resolve the wave, perfectly matched layer (PML) domains will have an appropriate mapped mesh, a boundary layer mesh is added for the exterior field, and periodic boundaries will be set up with copy mesh operations.
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First, select the Sequence Type as Physics-controlled mesh (the default) or User-controlled mesh, see Figure 2-7. When the user-controlled option is selected the mesh sequence nodes, generated by the physics, are shown and can be modified. For a fully user-defined mesh proceed and directly right-click the Mesh node, in the Model Builder tree, and add the first desired mesh element. The physics that contribute to the physics-controlled mesh generation can be selected in the Contributor list.
Figure 2-7: User interface of the Physics-controlled mesh options for Pressure Acoustics as seen on the Mesh node.
Resolving the wave in space (see also Meshing: Resolving the Waves in Space) requires and input of the maximum frequency solved for in the model. The way the frequency is picked up and how many elements are used to resolve the wave, can be controlled in the physics-controlled mesh user interface, see Figure 2-7.
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Select the Maximum mesh element size control parameter as From study (the default) or Frequency. For the default From study option, the maximum frequency will, for frequency domain problems, be picked up from the Frequencies list in the frequency domain study step; while for time domain problems the value is picked up from the Maximum frequency to resolve setting in the Transient Solver and Mesh Settings section. In the frequency domain case enter frequency values in the study step before generating the mesh. Alternatively select the Frequency option and manually enter the Maximum frequency. The manual input can be a good option in models with several studies to ensure that the mesh is the same for all.
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Select the Number of mesh elements per wavelength as Automatic (the default) or User defined. The Automatic option gives 5 elements per wavelength.
The mesh also needs to resolve the geometry details in the model. The overall refinement such as minimum mesh size, maximum element growth rate, curvature factor, and the resolution of narrow region values are controlled by the Element size option. The default is to use the Normal setting.
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Acoustic Scattering off an Ellipsoid. The Application Library path: Acoustics_Module/Tutorials,_Pressure_Acoustics/acoustic_scattering
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Absorptive Muffler. The Application Library path: Acoustics_Module/Automotive/absorptive_muffler
Physics-controlled mesh for the Pressure Acoustics, Frequency Domain and Pressure Acoustics, Transient was added in COMSOL Multiphysics version 6.0. Correct meshing of PMLs is supported for all acoustics physics, when applicable.
Meshing in the COMSOL Multiphysics Reference Manual