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.

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 5×(N×r) 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 N×1 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 N×M, 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.