aerocoeff

Mapdl.aerocoeff(aeromodetype='', aeromappedfilenames='', aerospecs='', aeroscalar='', nblades='', autofileread='', **kwargs)

Computes the aero-damping and stiffness coefficients and writes them to an APDL array.

APDL Command: AEROCOEFF

Parameters:

aeromodetype

Mode type to be used.

• "blade" : Non-cyclic cantilevered blade mode (default)

aeromappedfiles

Name of string array containing file names of mapped pressures from CFD. The file names should be ordered to correspond to the AeroSpecs array.

aerospecs

Name of numerical array containing data organized to correspond to the AeroMappedFiles array.

aeroscalar

Scaling value(s) to handle any modal scaling difference between structural and CFD modes. The values can be entered as a scalar or 1-dimensional array. (each scaling value defaults to 1)

nblades

Number of blades.

autofileread

Key to automatically read and use values from CFD file header.

• 0 (OFF or NO) : Do not read scaling values or nodal diameter from the CFD file header. (default)

• 1 (ON or YES) : Read scaling values (labeled Mode Multiplier in CFD file) from CFD file header. The scaling values read will be used in calculations and the AeroScalar input will be ignored. The nodal diameter values will be used to cross check the value of i (input through AeroSpecs array).

Notes

The AEROCOEFF command is designed to generate an array of aerodynamic coefficients that can be used in a cyclic mode-superposition harmonic response analysis using the CYCFREQ , AERO command to represent aerodynamic stiffness and damping. These aerodynamic coefficients can also be used in a damped modal analysis phase (CYCFREQ, MODAL) of a cyclic mode-superposition harmonic solve. An APDL array called JobnameAeroArray is generated using the AEROCOEFF command. This array is compatible with the array needed for the CYCFREQ, AERO command. The format of the written array follows that of the CYCFREQ, AERO command. The array is formatted as follows: i, m, n, V_real, V_imag

where i = the i th interblade phase angle (IBPA) m = the m th vibrating blade mode n = the n th blade mode generating the pressure oscillations

Vreal and V_imag = the real and imaginary coefficients.

Prior to issuing the AEROCOEFF command, a non-cyclic cantilevered blade modal analysis must be run, either stress-free or prestressed using linear perturbation. For more information, see Modal Analysis in the Structural Analysis Guide. The file requirements for the AEROCOEFF command are the same as those needed for modal restart as described in Modal Analysis Restart. The AeroSpecs values are specified in a 3×r array *DIM, where r is a positive integer equal to the number of interblade phase angles and the pressure modes solved for in the CFD analysis.

Each row has the structure: i, m, n where i = the i th interblade phase angle (IBPA) m = the m th vibrating blade mode n = the n th blade mode generating the pressure oscillations

At least one aerodynamic damping coefficient must be specified for each IBPA (equal to the number of blades) while keeping and constant. If a value is not specified, the program writes an array value of zero for both and . The values of and are relative to the modes computed in the re- quired modal analysis.

The number of AeroScalar values must be equal to the number of pressure modes ( from Aero- Specs). If the number of AeroScalar values is greater than 1, the values must be entered by defining an array *DIM and entering the array name in the AeroScalar field. For a discussion of how AeroScalar values are computed, see Scaling Aerodynamic Coupling Coefficients.

The value for nBlades should be equal to the number of sectors of the system. If there are multiple blades per cyclic sector, then the combination of blades on the single sector will have an aero coefficient value. In this case, each blade will not have a distinct aero coefficient.