3.24. Low Reduced Frequency Model

This acoustic model enables you to account for the interaction between an acoustic pressure wave in a viscous fluid and a rigid wall for specific structures according to Low Reduced Frequency (LRF) approximation. For additional information, see the Low Reduced Frequency (LRF) Model topic in the Mechanical APDL Acoustic Analysis Guide.

Guidelines

See Low Reduced Frequency for guidelines in using a Low Reduced Frequency Model in an acoustic simulation.

Analysis Types

Low Reduced Frequency Model is an Acoustics Model that is available for the following analysis types.

Common Characteristics

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

Dimensional Types

  • 3D Simulation: Supported.

  • 2D Simulation: Not Supported.

Scoping: The Low Reduced Frequency Model model is scoped bodies.

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 Low Reduced Frequency:

  1. On the Environment Context tab: select Acoustic Models > Low Reduced Frequency Model. Or, right-click the Environment tree object or click in the Geometry window and select Insert > Acoustics > Low Reduced Frequency Model.

  2. Define body scoping.

Details View Properties

The selections available in the Details view are described below.

CategoryFields/Options/Description
Definition

Type: Read-only field that describes the object - Low Reduced Frequency Model.

Model Type: This property specifies the type of structure to be represented. It provides a drop-down with the options: Thin Layer (default), Rectangular Tube, and Circular Tube. Based on the Model Type property selection, one of the following properties displays:

  • Thickness Of Layer: Enter a thickness value.

  • Width Of Rectangle and Height Of Rectangle: enter width and height values.

  • Radius Of Circle: Enter a radius value.

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

Mechanical APDL References and Notes

The Low Reduced Frequency Model is applied using the command:

TB,AFDM,,,,TBOPT

Where:

  • TBOPT = THIN for Model Type = Thin Layer.

  • TBOPT = RECT for Model Type = Rectangular Tube.

  • TBOPT = CIRC for Model Type = Circular Tube.

API Reference

See the Low Reduced Frequency section of the ACT API Reference Guide for specific scripting information.