cycfreq

Mapdl.cycfreq(option='', value1='', value2='', value3='', value4='', value5='', **kwargs)

Specifies solution options for a cyclic symmetry mode-superposition

APDL Command: CYCFREQ harmonic analysis.

Parameters:

option

One of the following options:

AERO

Specify the array containing the aerodynamic damping coefficients.

Value1

The name of the array containing the aerodynamic stiffness damping coefficients.

BLADE

Blade information required for a mistuning analysis.

Value1

The name of the nodal component containing the blade boundary nodes at the blade-to-disk interface. Also include boundary nodes at any shroud interfaces.

Value2

The name of the element component containing the blade elements.

Value3

The number of blade modes to include in the CMS reduction.

Value4

The lower bound of the frequency range of interest. This value is optional.

Value5

The upper bound of the frequency range of interest. This value is optional.

DEFAULT

Set the default cyclic harmonic solution settings.

EO

Excitation engine order.

Value1

The value of the excitation order, which must be an integer. The loadings on the other sectors will be related to the loading on the basic sector based on the engine order phase shift.

Value2

The name of the Mechanical APDL array containing the modal forces corresponding to the modes kept in the mode-superpostion analysis.

MIST

Mistuning parameters.

Value1

The type of mistuning:

K

Stiffness (frequency) mistuning

Value2

The name of the array containing the stiffness mistuning parameters.

MODAL

Specifies if a damped modal analysis should be performed on the reduced system.

Value1

On/Off key.

0 (OFF or NO)

No modal solution. Perform the harmonic solution.

1 (ON or YES)

Perform a damped modal analysis of the reduced system in order to obtain the complex frequencies. The harmonic solution is not performed.

Value2

Number of modes for the damped modal analysis.

Value3

The beginning, or lower end, of the frequency range of interest (in Hz).

Value4

The ending, or upper end, of the frequency range of interest (in Hz).

RESTART

Defines the point at which to restart the harmonic analysis.

Value1

The restart point:

OFF

No restart (default)

SWEEP

Restart for a new frequency sweep range (HARFRQ)

MIST

Restart for new mistuning parameters (new mistuning arrays)

USER

Causes the program to call for a user-defined solution.

Value1-5

Values passed down to the user-defined solution.

STATUS

List the harmonic solution option settings active for the cyclic model.

Notes

The program solves a cyclically symmetric model (set up via the CYCLIC command during preprocessing) at the harmonic indices specified via the CYCOPT command.

The aerodynamic coefficients are specified in a 5x(Nxr) array (*DIM), where N is the number of blades and r can be any positive integer. Each column has the structure:

where:

One aerodynamic damping coefficient must be specified for each IBPA (equal to the number of blades) while keeping m and n constant.

For constant (frequency-independent) mistuning, the stiffness parameters are specified in an Nx1 array (*DIM) where N is the number of blades.

For stiffness mistuning, each row entry represents the deviation of Young’s modulus from nominal, (or equivalently, the ratio of the frequency deviation squared). Each frequency can also be independently mistuned, in which case the array is NxM, where M is the number of blade frequencies (Value3 of CYCFREQ,BLADE). The entries in each row therefore correspond to the ratio of the mistuned frequency to the tuned frequency squared minus one:

The USER option activates the solution macro CYCMSUPUSERSOLVE.MAC. The normal solution is skipped. You may implement your own mistuning solution using APDL and APDL Math operations, or call your own program for the solution.

The CYCFREQ command is valid in the preprocessing and solution stages of an analysis.

The CYCFREQ,MODAL,ON command writes modal frequencies to the output file. No other postprocessing is available for this modal solve.

When using CYCFREQ,RESTART, only mistuning parameters or frequency range may be changed. All other changes in parameters are ignored.

To learn more about analyzing a cyclically symmetric structure, see the Cyclic Symmetry Analysis Guide.