Mode Analysis
The Mode Analysis () study and study step are used to compute the propagation constants or wave numbers as well as propagating mode shapes for a given frequency.
For example, in electromagnetics, it is used to compute the propagation constants and mode shapes at ports and waveguide cross sections. In acoustics, it is used to compute the propagation constants and mode shapes at inlets, outlets, and cross sections of guiding structures such as ducts.
When you add a Mode Analysis study, it adds a Mode Analysis study step under the Study node. The Mode Analysis study is available with the Acoustics Module, RF Module, or Wave Optics Module.
Study Settings
Select a method to Transform: Effective mode index or Phase velocity, Out-of-plane wave number, or None. The available transforms and the default transform depend on the physics interfaces in the study.
Enter a value or expression for the Mode analysis frequency. The default frequency depends on the physics interfaces in the study.
From the Mode search method list, select a search method:
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Manual (the default), to specify some search criteria manually. See Manual Mode Search Settings below.
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Region, to define a mode search region in a complex plane. See Mode Search Region Settings below.
Manual Mode Search Settings
Use the Desired number of modes field to specify the number of modes you want the solver to return (default: 6).
In the Search for modes around field, you can specify a value or expression around which the eigenvalue solver should look for solutions to the eigenvalue equation (default: 1).
Use the Mode search method around shift list to control how the eigenvalue solver searches for modes around the specified shift value:
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Select Closest in absolute value (the default value) to search for modes that are closest to the shift value when measuring the distance as an absolute value.
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Select Larger real part to search for modes with a larger real part than the shift value.
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Select Smaller real part to search for modes with a smaller real part than the shift value.
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Select Larger imaginary part to search for modes with a larger imaginary part than the shift value.
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Select Smaller imaginary part to search for modes with a smaller imaginary part than the shift value.
Mode Search Region Settings
Use the Approximate number of modes field to specify the approximate number of modes you want the solver to return (default: 20).
In the Maximum number of modes field, you can specify a maximum number of modes to limit the eigenvalue solver’s search for additional modes (default: 200).
The Perform consistency check check box is selected by default to increase confidence that the solver finds all modes in the search region.
Under Search region, you define the size of the search region for modes as a rectangle in the complex plane by specifying the Smallest real part, Largest real part, Smallest imaginary part, and Largest imaginary part in the respective text fields. The search region also works as an interval method if the Smallest imaginary part and Largest imaginary part are equal; the eigenvalue solver then only considers the real axis and vice versa.
Study Extensions
This section contains some optional extensions of the study, such as auxiliary sweeps (see Common Study Step Settings). Adding an auxiliary parametric sweep adds an Eigenvalue Parametric attribute node to the Eigenvalue Solver.
Distribute Parametric Solver
If you are running an auxiliary sweep and want to distribute it by sending one parameter value to each compute node, select the Distribute parametric solver check box. To enable this option, click the Show More Options button () and select Batch and Cluster in the Show More Options dialog box.
The Physics and Variables Selection, Values of Dependent Variables, Mesh Selection, Adaptation and Error Estimates, and Geometric Entity Selection for Adaptation sections and the Include geometric nonlinearity check box are described in Common Study Step Settings. There is also detailed information in the Physics and Variables Selection and Values of Dependent Variables sections.
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With the Acoustics Module: Eigenmodes in a Muffler, Application Library path Acoustics_Module/Automotive/eigenmodes_in_muffler.
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With the Wave Optics Module: Stress-Optical Effects in a Photonic Waveguide, Application Library path Wave_Optics_Module/Waveguides_and_Couplers/stress_optical.