PMLOPT

PMLOPT, PSYS, Lab, Xminus, Xplus, Yminus, Yplus, Zminus, Zplus, WOptXm, WOptXp, WOptYm, WOptYp, WOptZm, WOptZp
Defines perfectly matched layers (PMLs) or irregular perfectly matched layers (IPML).

PREP7: Artificially Matched Layers

PSYS

PML element coordinate system number. PSYS may be 0 (global Cartesian) or any previously defined local Cartesian coordinate system number (>10). Defaults to 0. (Not used for IPML.)

Lab

Label defining the number of dimensions (not used for IPML):

ONE	—	A one-dimensional PML region.
THREE	—	A three-dimensional PML region (default).

Xminus

For PML, normal reflection coefficient (harmonic analysis) or attenuation factor (static structural analysis) in negative X direction of PSYS. Defaults to 1.E−3 (equivalent to -60 dB) for WOptXm = PROP or HYBR, 30 for WOptXm = EVAN, and 40 for WOptXm = MAXP.

Xplus

Normal reflection coefficient (harmonic analysis) or attenuation factor (static structural analysis) in positive X direction of PSYS. Defaults to 1.E−3 (equivalent to -60 dB) for WOptXp = PROP or HYBR, 30 for WOptXp = EVAN, and 40 for WOptXp = MAXP. (Not used for IPML.)

Yminus

Normal reflection coefficient (harmonic analysis) or attenuation factor (static structural analysis) in negative Y direction of PSYS. Defaults to 1.E−3 (equivalent to -60 dB) for WOptYm = PROP or HYBR, 30 for WOptYm = EVAN, and 40 for WOptYm = MAXP. (Not used for IPML.)

Yplus

Normal reflection coefficient (harmonic analysis) or attenuation factor (static structural analysis) in positive Y direction of PSYS. Defaults to 1.E−3 (equivalent to -60 dB) for WOptYp = PROP or HYBR, 30 for WOptYp = EVAN, and 40 for WOptYp = MAXP. (Not used for IPML.)

Zminus

Normal reflection coefficient (harmonic analysis) or attenuation factor (static structural analysis) in negative Z direction of PSYS. Defaults to 1.E−3 (equivalent to -60 dB) for WOptZm = PROP or HYBR, 30 for WOptZm = EVAN, and 40 for WOptZm = MAXP. (Not used for IPML.)

Zplus

Normal reflection coefficient (harmonic analysis) or attenuation factor (static structural analysis) in positive Z direction of PSYS. Defaults to 1.E−3 (equivalent to -60 dB) for WOptZp = PROP or HYBR, 30 for WOptZp = EVAN, and 40 for WOptZp = MAXP. (Not used for IPML.)

WOptXm, WOptXp, WOptYm, WOptYp, WOptZm, WOptZp

Type of attenuated wave in the PML region in each direction:

PROP	—	Only the propagating wave is attenuated. The PML parameter is set to s = 1–jβ in harmonic analyses and acoustic transient analyses.
EVAN	—	Only the evanescent field is attenuated. The PML parameter is set to s = α (α > 1) in static analyses.
HYBR	—	Both the propagating wave and the evanescent wave are attenuated (default). The PML parameter is set to s = α–jβ (α > 1). The program sets the coefficient α values in terms of the normal reflection coefficients in harmonic analyses.
MAXP	—	The maximum attenuation coefficient for frequency-independent PML parameter in harmonic analyses, acoustic modal analyses, and acoustic transient analyses.

Notes

The PMLOPT command can be used to define perfectly matched layers (PML). The following element types support perfectly matched layers:

Acoustic elements: FLUID30, FLUID220, and FLUID221 (KEYOPT(4) > 0) in a modal, harmonic, or transient acoustic analysis.
Piezoelectric coupled-field elements: PLANE222, PLANE223, SOLID225, SOLID226, and SOLID227 (KEYOPT(15) = 1) in a harmonic piezoelectric analysis. For the lower order elements (PLANE222 and SOLID225), PML is only supported with the B-bar method.
Structural elements: PLANE182, PLANE183, SOLID185, SOLID186, and SOLID187 (KEYOPT(15) = 1) in a linear static or harmonic structural analysis. For the lower order elements (PLANE182 and SOLID185), PML is only supported with the B-bar method.

Each PML region must have a uniquely defined PML element coordinate system (PSYS). Normal reflection coefficient values for a harmonic analysis must be less than 1.

The PMLOPT command can also be used to define irregular perfectly matched layers (IPML) for acoustic analyses. Normal reflection coefficient values for a harmonic analysis must be less than 1.

Issue PMLOPT,STAT to list the current normal reflection coefficient or attenuation factor settings for a PML or IPML region. Issue PMLOPT,CLEAR to clear all normal reflection coefficient settings and restore them to the defaults.

Issue PMLOPT,PSYS,CLEAR to clear all normal reflection coefficient settings for the specified PML element coordinate system and restore them to the defaults.

For modal analysis, use one buffer element between the PML and the resonant structure to avoid the spurious modes. The mode patterns should be evaluated graphically.

See Artificially Matched Layers in the Acoustic Analysis Guide for more information about using perfectly matched layers (PML) and irregular perfectly matched layers (IPML).

Menu Paths

This command cannot be accessed from a menu.