3.2. Surface Velocity

A Surface Velocity loading condition applies a velocity to a surface on your model.

Analysis Types

The Surface Velocity excitation condition is available for Coupled Field Harmonic and Harmonic Acoustics analyses.

Common Characteristics

This section describes the characteristics of the excitation 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 Surface Velocity 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 Surface Velocity.

Body: Not Supported.
Face: Supported.
Edge: Not Supported.
Vertex: Not Supported.
Nodes: Not Supported.
Element Face: Not Supported.
Element: Not Supported.

Loading Types: The boundary condition’s loading is defined using one of the following options.

Normal To
Components

Loading Data Definition: Enter loading data as:

Constant
Tabular (Frequency Varying)

Boundary Condition Application

To apply a Surface Velocity:

On the Environment Context tab: click Acoustic Excitations>Surface Velocity. Or, right-click the Environment tree object or in the Geometry window and select Insert>Acoustic>Surface Velocity.
Define the Scoping Method. Options include Geometry Selection (default) and Named Selection. For either scoping type, you must use the Body selection filter (on the Graphics Toolbar) for geometry selection or Named Selection definition. Only bodies specified in the acoustics Physics Region(s) can be selected or defined.
Select the method used to define the load: Normal To (default) or Components.
Define the Magnitude.

Note: When you define multiple Surface Velocities there is no cumulative loading effect. Therefore, if you define multiple Surface Velocities on the same face, only the last Surface Velocity, as defined in the input file, is used to calculate results.

Details View Properties

The selections available in the Details view are described below.

Category	Fields/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 (Face only) selections must be made on faces 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 - Surface Velocity. Define By, options include: Normal To: This option requires Magnitude and Phase Angle entries. Components: this option defines the loading type as components in the Global Coordinate System or a user-defined local coordinate system. Requires the specification of at least one of the following inputs: X Component: Defines magnitude in the X direction. Y Component: Defines magnitude in the Y direction. Z Component: Defines magnitude in the Z direction. X Phase Angle Y Phase Angle Z Phase Angle Magnitude Phase Angle: Suppressed: Include (No - default) or exclude (Yes) the boundary condition.

Mechanical APDL References and Notes

Application of Acoustic Surface Velocity is based on how you define it:

If Define By = Normal To, the application uses the SHLD label of SF command. This defines surface normal velocity.
If Define By = Components, the application uses the VELO label of BF command.

For more information, refer to the Outward Normal Velocity and the Arbitrary Velocity sections in the Mechanical APDL Acoustic Analysis Guide.

API Reference

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