ABAQUS Keywords Reference Manual  

*IMPEDANCE PROPERTY
Define the impedance parameters for an acoustic medium boundary.

This option is used to define the proportionality factors between the pressure and the normal components of surface displacement and velocity in acoustic analysis. The *IMPEDANCE PROPERTY option must be used in conjunction with the *INCIDENT WAVE REFLECTION, *IMPEDANCE, or *SIMPEDANCE option.

Products: ABAQUS/Standard  ABAQUS/Explicit  

Type: Model data

Level: Model  

References:

Required parameter:

NAME

Set this parameter equal to a label that will be used to refer to the impedance property on the *INCIDENT WAVE REFLECTION, *IMPEDANCE, or *SIMPEDANCE option.

Optional parameters:

INPUT

Set this parameter equal to the name of the alternate input file containing the data lines for this option. See “Input syntax rules,” Section 1.2.1 of the ABAQUS Analysis User's Manual, for the syntax of such file names. If this parameter is omitted, it is assumed that the data follow the keyword line.

TYPE

Set TYPE=TABULAR (default) to specify an impedance using a table of admittance values.

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

Set TYPE=SPHERE to specify a radiation condition appropriate for a spherical boundary.

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

Set TYPE=PROLATE SPHEROID to specify a radiation condition appropriate for a prolate spheroidal boundary.

If this parameter is omitted, it is assumed that the data following the keyword line are entries in a table of explicitly stated admittance values.

If the *IMPEDANCE PROPERTY option is used in conjunction with the *INCIDENT WAVE REFLECTION option, the TYPE parameter must be set equal to TABULAR.

Data lines to define an impedance (TYPE=TABULAR): 

First line:

  1. , the proportionality factor between pressure and displacement of the surface in the normal direction. This quantity is the imaginary part of the complex admittance, divided by the angular frequency; see “Acoustic loads,” Section 19.4.5 of the ABAQUS Analysis User's Manual. (Units of F–1L3.)

  2. , the proportionality factor between pressure and velocity of the surface in the normal direction. This quantity is the real part of the complex admittance. (Units of F–1L3T–1.)

  3. Frequency. (Cycles/time.) Frequency dependence is active only during frequency domain analysis in ABAQUS/Standard.

Repeat this data line as often as necessary in ABAQUS/Standard to describe the variation of the coefficients with frequency. Only the first line entered will be used in direct-integration procedures.

Data line to define an absorbing boundary impedance of TYPE=CIRCULAR or TYPE=SPHERE: 

First (and only) line:

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

Data line to define an absorbing boundary impedance of TYPE=ELLIPTICAL or TYPE=PROLATE SPHEROID: 

First (and only) line:

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

  2. 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, , to the major axis, : .

  3. Global -coordinate of the center of the radiating surface.

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

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

  6. -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.

  7. -component of the direction cosine of the major axis of the radiating surface.

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