3.13. Absorption Surface

The Absorption Surface boundary condition enables you to dampen the effect of sound pressure on the impedance boundary as well as to approximate infinity.

Analysis Types

The Absorption Surface loading condition is available for Coupled Field Harmonic, Coupled Field Modal, Coupled Field Transient, Harmonic Acoustics, and Modal Acoustics analyses.

Common Characteristics

This section describes the characteristics of the boundary condition, including the application requirements, support limitations, and loading definitions and values.

Types Supported

  • 3D Simulation: Supported.

  • 2D Simulation: Not Supported.

Geometry Types: Geometry types supported for the Absorption Surface boundary condition include:

  • Solid: Supported.

  • Surface/Shell: Not Supported.

  • Wire Body/Line Body/Beam: Not Supported.

Topology: The following topology selection options are supported for Absorption Surface.

  • Body: Not Supported.

  • Face: Supported.

  • Edge: Not Supported.

  • Vertex: Not Supported.

  • Nodes: Not Supported.

  • Element: Not Supported.

  • Element Face: Not Supported.

Loading Data Definition: Enter loading data using one of the following options.

  • Constant

  • Tabular (Frequency Varying): Supported for Harmonic Acoustics only.

Boundary Condition Application

To apply a Absorption Surface:

  1. On the Environment Context tab: click Acoustic Boundary Conditions>Absorption Surface. Or, right-click the Environment tree object or in the Geometry window and select Insert>Acoustics Absorption Surface.

  2. Define the Scoping Method.

  3. Define an Absorption Coefficient.

Details View Properties

The selections available in the Details view are described below.

CategoryFields/Options/Description
Scope

Scoping Method, options include:

  • Geometry Selection: Default setting, indicating that the boundary condition is applied to a geometry or geometries, which are chosen using a graphical selection tools.

    • Geometry (Face selection only): Visible when the Scoping Method property is set to Geometry Selection. Geometry selections must be made on bodies specified in the acoustic Physics Region.

      Use the Face selection filter to pick your geometry, click in the Geometry field, and then click the Apply button that displays. After you select the geometry, this property displays the geometric entities (1 Face, 3 Faces, etc.).

  • Named Selection: Indicates that the geometry selection is defined by a Named Selection.

    • Named Selection: Visible when the Scoping Method is set to Named Selection. This field provides a drop-down list of available user–defined Named Selections (face-based only).

Definition

Type: Read-only field that describes the object - Absorption Surface.

Absorption Coefficient: Specify an Absorption Coefficient value for the selected boundary. This property can be designated as a parameter.

Suppressed: Include (No - default) or exclude (Yes) the boundary condition.

Mechanical APDL References and Notes

This boundary condition is applied using the SF command. Refer to the Boundary with Absorption Coefficient description in the Mechanical APDL Acoustic Analysis Guide for more information.

API Reference

See the Absorption Surface section of the ACT API Reference Guide for specific scripting information.