Simcenter Nastran FEM acoustics

You can use Simcenter Nastran FEM acoustic and vibro-acoustic solutions to perform interior or exterior acoustic analyses. You can model both fluid and structural meshes for a coupled vibro-acoustic analysis, or you can define a fluid-only mesh to perform a pure acoustic analysis. The Simcenter Nastran FEM acoustic formulation is linear, and assumes no flow of the fluid medium.

You model the 3D fluid mesh with CHEXA, CTETRA, CPENTA, or CPYRAM solid elements, which reference a fluid property and material definition. Each fluid node includes a pressure degree-of-freedom. If your model includes both fluid and structure meshes, you can request the software to automatically couple the fluid and structure. You can also define acoustic absorber elements on the structural surfaces to represent a soundproofing material.

To represent a region exterior to the fluid and structure medium, you can use an Automatically Matched Layer (AML) and a microphone mesh. The AML represents the non-reflective acoustic boundary condition at the free fluid boundary.

Defining an acoustic surface impedance or admittance

In an acoustic or vibro-acoustic solution, you can define acoustic surface impedance (or its reciprocal admittance) by creating an Acoustic Absorber. You apply an acoustic absorber on the free faces of fluid elements. The Acoustic Absorber corresponds to the Simcenter Nastran CAABSF and PAABSF bulk entries.

Defining structural panels

To compute contributions of structural panels to acoustic pressure results, you can create a Panel in vibro-acoustic solutions. A panel contains entities of 2D or 3D meshes. It corresponds to the PANEL bulk entry.

You can create panels with the following commands:

• Panel — Lets you manually create structural panels.

• Mapped Panel — Lets you automatically create structural panels from groups of acoustic fluid nodes that are mapped to structural nodes. You can also use this command to export the panels to an external file. You can use the exported file in your own panel contribution analysis application.This command is more efficient than the Panel command when groups of acoustic fluid nodes already exist.

Coupling acoustic and structural elements

In a vibro-acoustic solution, to specify the acoustic and structural elements that need to be coupled, create a Fluid-Structure Interface Modeling Parameters modeling object, which corresponds to the ACMODL bulk data entry. You can define the wetted surface by selecting the acoustic and structural elements to be coupled.

Defining fluid-structure interaction

You can create a Fluid-Structure Interaction Control Parameters modeling object, which corresponds to the FLSTCNT bulk data entry, in both acoustic and vibro-acoustic solutions.

Defining modal damping

In the vibro-acoustic SOL 111 solution, you can define modal damping separately for structural and for acoustic entities. You can define Modal Damping groups on the:

• Case Control tab of the Solution dialog box

• Solution Step dialog box for each subcase

You can define uniform structural damping and uniform fluid damping in the damping parameter groups on the Bulk Data tab of the Solution dialog box. These options correspond to the KDAMP,KDAMPFL and G,GFL parameters.

Defining modal contributions

You can define the modal contribution parameters in acoustic or vibro-acoustic solutions. You can request acceleration, velocity, displacement, or pressure results along with modal contributions in the Acoustic Output Requests or Vibro-Acoustic Output Requests for the solution. The Modal Contribution output request corresponds to the MODCON case control command.

In a vibro-acoustic solution, you can request modal contributions separately for the structural modes and fluid modes.

You can request SORT1 and SORT2 results. However, only SORT2 results are supported for display in Pre/Post. You can view the SORT2 results in the XY Function Navigator. The SORT1 results can be in the form of PRINT and/or PUNCH. Simcenter Nastran then writes the results to the f06 or to the PCH file, respectively.

Defining panel contributions

You can define the panel contribution parameters in a vibro-acoustic solution. You can request acceleration, velocity, displacement, or pressure results along with panel contributions in the Vibro-Acoustic Output Requests for the solution. The Panel Contribution output request corresponds to the PANCON case control command.

• In the Number of Structural Panels to List field, you can define the number of most-contributing panels for which the contributions to the requested responses are computed.

• In the Number of Structural Nodes to List field, you can define the number of most-contributing nodes for which the contributions to the requested responses are computed.

• In the Panels for Contributions option, you can define for which panels the contributions to the requested output are computed. There are two options: ALL panels (as defined in the bulk section) or one panel (to be selected from the list of available panels).

Acoustic and Vibro-Acoustic analysis types

When you create a Simcenter Nastran solution, two analysis types are available:

• Acoustic — Only 3D Acoustic Fluid elements are available in this environment.

• Vibro-Acoustic — Both 3D Acoustic Fluid elements and structural elements are available in this environment.

Limiting output to peak responses

In vibro-acoustic analysis, you can limit the results that are output to those responses that have the highest magnitude.

For more information, see Limiting frequency response output to peak responses.

Supported Simcenter Nastran solutions

The following solution types are supported with both acoustic and vibro-acoustic solutions:

• SOL 103 – Real Eigenvalues

• SOL 107 – Direct Complex Eigenvalues

• SOL 108 – Direct Frequency Response

• SOL 110 – Modal Complex Eigenvalues

• SOL 111 – Modal Frequency Response

Where do I find it?

Application	Pre/Post
Prerequisites	Simcenter Nastran as the specified solver.A Simulation file as the work part and displayed part.
Menu	Insert→Solution
Location in dialog box	Solution dialog box→Analysis Type list→select Acoustic or Vibro-Acoustic

Learn more

FEM acoustics workflow

FEM vibro-acoustic workflow

Checking your FEM acoustics model prior to solving

Electric motor vibro-acoustics analysis workflow

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

Browse Simcenter 3D help by product area

Simcenter Nastran FEM acoustics, Simcenter 3D 2021.1 Series

© 2020 Siemens

window.mainLanguage="en_US"

window.delivId=""

window.projectId=""

MathJax.Hub.Config({ TeX: { extensions: ["autoload-all.js"] }, tex2jax: { displayMath: [ ] }, "SVG": { scale: 125 } });