Mesh primitives for acoustics and vibro-acoustics analysis

You can create a mesh primitive to define the parameters of a targeted shape and have the software generate a mesh that approximates that shape. You can use mesh primitives to quickly generate a mesh in a pre-defined geometric form, such as a box or a cylinder, without first creating any geometry. You create mesh primitives relative to a local coordinate system that you select and with key dimensions that you specify. For example, with a Sphere mesh primitive, you define the center point and radius for the sphere, and the software generates a 2D mesh to represent the sphere's geometry.

You can use mesh primitives to create:

• A structural mesh or a microphone mesh in a Simcenter Nastran FEM or Simcenter 3D Acoustics BEM model. For more information on microphones, see Using microphone mesh to capture analysis results.

• A boundary element mesh in a Simcenter 3D Acoustics BEM model.

Using mesh primitives to model microphones and microphone arrays

In an acoustics or vibro-acoustics analysis, you can use mesh primitives to model microphones and arrays of microphones:

• A microphone represents a location where acoustic power is measured.

• A microphone array defines a connection relation between individual microphones.

When you use the mesh primitive commands to create microphones or microphone arrays, nodes represent microphones, and elements represent the connectivity between the microphones in the array. For example, you can create:

• A Point Set mesh primitive to model individual, isolated microphones that are not connected with 0D elements.

• A Line mesh primitive to model a connected pair of microphones with 1D elements.

• A Cylinder or Box Solid primitive to model microphone arrays with 2D or 3D elements

For descriptions of the different mesh primitive types, see Mesh primitive types for acoustics and vibro-acoustics analysis.

You can use a microphone mesh to compute acoustic power, such as the total acoustic power radiated from your structure. Acoustic power is computed from the net acoustic flux on the microphone mesh using acoustic pressure and particle velocity. For information on requesting acoustic results on the nodes that represent microphones, see Request output on a microphone mesh (FEM acoustics).

Supported element types and physical properties

When you create a mesh primitive to model a microphone or microphone array, the elements you can select depend on your specified solver and the type of primitive. For example, with the Simcenter 3D Acoustics solver, you create a Point Set primitive with POI1 Microphone elements. Similarly, when you create a Plane Mesh primitive with the Simcenter Nastran, solver, you can choose between the CQUAD4 - Microphone or the PLOTEL4 element.

Note:

Mesh primitives comprised of 2D and 3D elements are always modeled with linear elements.

For 1D, 2D, and 3D microphone elements in the Simcenter Nastran, Simcenter 3D Acoustics environments, the software automatically assigns a PMIC physical property table to the elements. The PMIC property table does not have any associated properties, but it indicates that the associated elements function as microphones and are not a structural part of the FE model.

Note:

When you define the size of elements to create in the mesh primitive, you can use the SizeForAcoustics function to specify the element size as a function of frequency, To ensure that large variations of pressure and particle velocity are not ignored in the computation, the elements in the microphone mesh must be small enough to accurately represent the acoustic response. For more information, see Element size for acoustic analysis.

Trimming mesh primitives with cutting planes

For certain types of mesh primitives, you can use cutting planes to trim the mesh primitive to the exact shape that you need for the analysis. For more information, see Trimming mesh primitives with cutting planes.

Previewing mesh primitives

In every mesh primitive dialog box, before you click OK or Apply to create the mesh primitive, you can use the Preview option to have the software preview the appearance of the primitive based on your current options. For performance purposes, the software limits the number of elements that you can dynamically preview. You can use the Maximum Number of Elements for Dynamic Preview customer default to adjust this limit.

Working with mesh primitives

The mesh that you create with the mesh primitives commands is entirely FE-based. You can use manual node and element commands to modify the mesh. For example, you can use Element Delete to remove selected elements from the mesh.

When you create a mesh primitive, the software stores the options and settings you used to create the primitive. If you edit the mesh primitive and change a setting, such as the element type or radius, the software recreates the mesh primitive with the new settings.

The software stores mesh primitives in the appropriate mesh collector node in the Simulation Navigator.

Where do I find it?

Application	Pre/Post
Prerequisites	A FEM file as the work part and displayed partSimcenter Nastran, Simcenter 3D Acoustics BEM, or Simcenter 3D Acoustics Transient BEM as the specified solver
Command Finder	Box Surface Mesh Primitive Box Solid Mesh Primitive Circle Mesh Primitive Cylinder Mesh Primitive Hemisphere Mesh Primitive ISO Power (ISO3744) Mesh Primitive Line Mesh Primitive Plane Mesh Primitive Point Set Mesh Primitive Sphere Mesh Primitive

Maximum Number of Elements for Dynamic Preview default

Menu	File→Utilities→Customer Defaults
Location in dialog box	Simulation→Pre/Post→Meshing→Mesh Primitives tab

Learn more

Mesh primitive types for acoustics and vibro-acoustics analysis

ISO Power (ISO3744) Mesh Primitives

Trimming mesh primitives with cutting planes

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Mesh primitives for acoustics and vibro-acoustics analysis, Simcenter 3D 2021.1 Series

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