Use the Modal Reduction () solver to produce a reduced-order model. The modal reduction solver uses precomputed eigenvalues and eigenvectors. This solver is automatically used when a Model Reduction has its Method set to Modal.

Also see The Modal Solver Algorithm for more information.

Use the Defined by study step list to specify if the settings are synchronized with the corresponding study step, or select User defined to specify all settings locally.

Use the Study type list to select the basic study type. Select:

For a Frequency Domain, Modal study, use the Frequencies field to enter a vector of frequencies that define the frequency-domain simulation. Only the first frequency is used. Click the Range button () to define a range of frequencies using the Range dialog. You can also specify a unit in the Frequency unit list (default: Hz).

Use the Linearity list to specify the type of linear behavior. Select:

For a Time Dependent, Modal study, select a Time unit from the list. Then use the Output times field to enter a vector of times that define the time span for the simulation. Click the Range button () to define time values. For a time-dependent study type, the following additional settings are available:

Use the Relative tolerance field to enter a positive number (default value: 0.01). The relative tolerance is copied to the Reduced-Order Modeling node when a new node is created, where it can be further modified for use in the online phase for a stateless interface. When the interface is stateful this tolerance is not used. The absolute tolerance settings below work in the same way as for the time-dependent solver, but internally the full length absolute tolerance vector is transferred to the modes by the same transformation (projection) as is used to transform the problem to reduced form (the eigenmodes).

From the Extend basis with initial data list choose Automatic, On, or Off. If it is On, it means that initial data will be considered in the base extension. You can use On for rare cases where the automatic method does not add the initial values to the basis but it makes sense to do so. If it is Off, then initial data will no be considered. The default is Automatic, which means that the initial data will be considered in the base extension only if it is large enough to make a difference.

Use the Solution list to specify a solver configuration to be used when constructing the reduced model.

Use the Eigenpairs list to specify which of the eigenpairs present in the solution to include when constructing the reduced model. The default setting is All, and the solver then uses all available eigenpairs. Select Manual to enter a space-separated list of Eigenpair numbers in the field.

Use the Solution list to specify which solution to be used when constructing the reduced model.

Use the Constraint modes list to specify which of the constraint modes present in the solution to include when constructing the reduced model. The default setting is All, and the solver then uses all available constraint modes. Select Manual to enter a space-separated list of constraint modes numbers in the Constraint modes numbers field.

When there is sensitivity solution to be chosen as constraint modes, a Use sensitivity solution checkbox is available. When selected, it means that the constraint modes are from the sensitivity analysis. To get a meaningful sensitivity solution, you need to make sure that the inputs in the Global Reduced-Model Inputs node are used in some boundaries in a Stationary study step. The sensitivity parameter should be set to zero in the Sensitivity node. When cleared, it means that the constraint modes are from an auxiliary sweep. To get meaningful parametric solutions, you need to define some training parameters and apply them at the boundaries of the Stationary study step. In the Auxiliary sweep settings in the Study Extensions section of the Stationary node, set one parameter to be 1 at a time and set all other parameters to be zero.

A frequency-domain problem solved by the Modal Solver is assumed to be a linearization about a solution. You can specify such a solution (a linearization point) with the Prescribed by list. Select:

From the Reduced-order model list, choose New to create a new reduced-order model, or choose any existing reduced-order model.

From the Interface list, if you chose New from the Reduced-order model list, choose Stateless (the default) or Stateful. In the former case, the reduced-order model acts as a black box that uses an internal solver and does not expose its state. In the latter case, the reduced-order model exposes a set of reduced-order equations and state DOFs to the solver used for the calling model, and you can choose whether to solve for the reduced-order model in the same way as for a physics interface.

The Ensure reconstruction capability checkbox is selected by default to enable reconstruction of the unreduced solution vector. Clear it if you need to save memory; for the ROM to be capable of reconstruction, the modal basis must be stored.

Select the Allow complex numbers checkbox to be able to solve problems that are not automatically determined to be complex-valued in a correct way.

In this section you can define constants that can be used as temporary constants in the solver. You can use the constants in the model or to define values for internal solver parameters. These constants overrule any previous definition (for example, from Global Definitions). The constant values are expressions and can, for example, include the range() operator, units, and global expressions. The constant name can be a new or an existing global parameter. The constant is temporary in the sense that it is only defined during the solver run. You cannot override parameters used in the following parts of the model:

Click the Add button () to add a constant and then define its name in the Constant name column and its value (a numerical value or parameter expression) in the Constant value column. By default, any defined parameters are first added as the constant names, but you can change the names to define other constants. Click Delete () to remove the selected constant from the list.

Select the Keep warnings in stored log checkbox if you want the warnings to remain in the log for troubleshooting or other use.