Abaqus Keywords Reference Guide  
How to find keyword examples

*SIMPEDANCE
Define impedances of acoustic surfaces.

This option is used to provide surface impedance information or nonreflecting boundaries for acoustic and coupled acoustic-structural analysis.

Products: Abaqus/Standard  Abaqus/Explicit  Abaqus/CAE  

Type: History data

Level: Step

Abaqus/CAE: Interaction module

References:

Required, mutually exclusive parameters: 

PROPERTY

Set this parameter equal to the name of the *IMPEDANCE PROPERTY option defining the table of impedance values to be used.

NONREFLECTING

Set NONREFLECTING=PLANAR (default) to specify the impedance corresponding to that of a normal incidence plane wave.

Set NONREFLECTING=IMPROVED to specify the impedance corresponding to that of a plane wave at an arbitrary angle of incidence. This parameter can be used only for transient dynamics.

Set NONREFLECTING=CIRCULAR to specify a radiation condition appropriate for a circular boundary in two dimensions or a right circular cylinder in three dimensions.

Set NONREFLECTING=SPHERICAL to specify a radiation condition appropriate for a spherical boundary.

Set NONREFLECTING=ELLIPTICAL to specify a radiation condition appropriate for an elliptical boundary in two dimensions or a right elliptical cylinder in three dimensions.

Set NONREFLECTING=PROLATE SPHEROIDAL to specify a radiation condition appropriate for a prolate spheroidal boundary.

Optional parameter:

OP

Set OP=MOD (default) to modify existing impedances or to define additional impedances.

Set OP=NEW if all existing impedances applied to the model should be removed. To remove only selected impedances, use OP=NEW and respecify all impedances that are to be retained.

Data line to define an impedance for PROPERTY, NONREFLECTING=PLANAR, or NONREFLECTING=IMPROVED: 

First (and only) line:

  1. Surface name.

Data line to define an absorbing boundary impedance for NONREFLECTING=CIRCULAR or NONREFLECTING=SPHERICAL: 

First (and only) line:

  1. Surface name.

  2. , the radius of the circle or sphere defining the absorbing boundary surface.

Data line to define an absorbing boundary impedance for NONREFLECTING=ELLIPTICAL or NONREFLECTING=PROLATE SPHEROIDAL: 

First (and only) line:

  1. Surface name.

  2. The semimajor axis, a, of the ellipse or prolate spheroid defining the surface. a is 1/2 of the maximum distance between two points on the ellipse or spheroid, analogous to the radius of a circle or sphere.

  3. The eccentricity, , of the ellipse or prolate spheroid. The eccentricity is the square root of one minus the square of the ratio of the minor axis, b, to the major axis, a: .

  4. Global X-coordinate of the center of the radiating surface.

  5. Global Y-coordinate of the center of the radiating surface.

  6. Global Z-coordinate of the center of the radiating surface.

  7. X-component of the direction cosine of the major axis of the radiating surface. The components of this vector need not be normalized to unit magnitude.

  8. Y-component of the direction cosine of the major axis of the radiating surface.

  9. Z-component of the direction cosine of the major axis of the radiating surface.