Using structural results as input to an Acoustics BEM vibro-acoustic solution

You can apply enforced displacements, velocities, or accelerations from structural analysis results to an Acoustics BEM vibro-acoustic solution by using visualization elements (PLOTELs) and a load recipe. The FEM results could be from a Nastran, ANSYS, Abaqus, or similar type of structural model. You can apply an acoustic load, such as force versus frequency, to the fluid-structure interface for one-way (weak), or two-way (strong) coupling. You can apply an acoustic load to the complete structure, or to a partially loaded structure.

You can use one-way (weak) fluid structure interface in the Acoustics BEM solution. You can apply enforced vibration (displacements, velocities, or accelerations) to the complete structure, or to part of the structure with a Load Recipe.

You can also use a two-way (strong) fluid structure interface when the load is a force and the structure is represented by a Mode Set.

Structural solution

The following workflow assumes a Simcenter Nastran analysis but you can use similar steps for other solvers.

Step	Summary	Detailed help topic
1.	Create PLOTELs on the structure surface.	Use Surface Coat to create 2D PLOTELs on the structure.The PLOTELs cover surfaces which touch the acoustic fluid domain.The software uses the PLOTELs to transfer the desired structural displacements, velocities, or accelerations to an Acoustics BEM analysis.	Visualization elements (PLOTELs) in assembly FEM files
2.	Create a new Simulation file.	Create or open a Simulation file and make it the work part.Set the Solver to Simcenter Nastran and the Analysis Type to Structural.	Create a new Simulation file
3.	Create a new solution.	Create a SOL108 Direct Frequency Response or SOL111 Modal Frequency Response solution.
4.	Create a load set and apply a load to the structure.	Apply a force or pressure to the structure.	Create a load setForce loadAdd a load to a load set
5.	Create a constraint set and define constraints.	Constrain the structure as needed.	Create a constraint setNastran, Simcenter 3D Multiphysics, Abaqus, ANSYS, and LS-DYNA structural constraintsAdd a constraint to a constraint set
6.	Create output requests.	Edit the solution and create output requests to specify the desired displacements, velocities, or accelerations to compute.	Requesting output for Nastran analyses
7.	Create the forcing frequency range.	Create the Forcing Frequencies to define the frequency domain.Note: The Forcing Frequencies should cover the entire frequency range of the structural modes you are interested in.	Specifying forcing frequencies for a frequency response analysis
8.	Solve the solution process.		Solve the model
9.	Post-process the results.	Choose Post-Processing Scenario to confirm a valid solution. Display function plots or contour plots of the results or use the Post Processing Navigator to display the structural deformations.	Scenario-based post-processingDeformed model displays

Acoustics BEM Indirect Vibro-acoustic solution

In this workflow, you will represent the fluid structure interface with 2D PLOTEL elements and the structure with 2D structural elements.

You then apply the structural loading only to the free surface 2D PLOTEL elements instead of the entire 3D mesh. You apply the structural model results as a load recipe, create a solution from the load recipe, add output requests, define the frequency domain, and solve the solution.

Step	Summary	Detailed help topic
Prepare the acoustic model
1.	Copy the FEM file and save it as a new FEM file or import the FEM to an assembly FEM.Open the new FEM or Assembly FEM.		Copying CAE files
2.	Remove the structural mesh from the solver list.	Select the structural mesh and choose Edit Mesh Associated Data. In the Mesh Properties group, clear the Export Mesh to Solver check box.	Mesh Associated Data dialog box
3.	Create a 2D structural mesh on the structure exterior.	Open the Surface Coat dialog box, select the structural mesh, and change the Element Type to TRI3 or QUA4 mesh.Note: This 2D structural mesh does not require any material or thickness assignment. The mesh is the structure surface touching the acoustic fluid.	Surface coat of 2D elements
4.	Modify the PLOTELs to acoustic elements.	Use Element Modify Type to change the PLOTELs to TRI3 Acoustic or QUA4 Acoustic elements.	Modifying the type of elements
5.	Define material for the acoustic elements.	Use Manage Materials to assign acoustic fluid material to the acoustic elements.	Assign a material using a mesh collector
6.	Create a microphone mesh using a mesh primitive or with manual methods.	Define microphone meshes in the model to measure pressure results.Menu, Insert, Mesh Primitives	Using microphone mesh to capture analysis resultsMesh primitives for acoustics and vibro-acoustics analysis
7.	Create a new Simulation file and make it the work part.	Select the FEM file and choose New Simulation.	New dialog box
8.	Create a new solution.	Set the Solver to Simcenter 3D Acoustics BEM, the Analysis Type to Indirect Acoustic, and the Solution Type to Vibro-Acoustic Response.	Solutions and solving
Create load recipe and solution and solve.
1.	Create a load recipe from imported data sources.	On the Home tab, choose the Properties group, Load Recipes.Import the solution results from the SOL108 or SOL111 structural analysis.	Create a load recipe from a data source
2.	Create a solution from the load recipe.	In the Simulation Navigator, Load Recipe Container, right-click the Load Recipe you just created and choose New Solution From Load Recipe.	Create a solution from a load recipe
3.	Edit the solution and define the solution method.	In the Solution dialog box, Indirect Acoustic Model Formulation group, Model Formulation list, set the solution method as: Standard, Fast Multipole, or H-Matrix.	Solution formulation methods for indirect acoustic analysis (Acoustics BEM)Solution dialog box (Acoustics BEM)
4.	Edit the solution parameters.	In the Solution dialog box, create a Forcing Frequencies modeling object, and optionally specify quadrature distance parameters to control the solution.Note: Create a frequency range that is inside the minimum and maximum frequencies of the structural solution. Solving for acoustic frequencies outside the structural solution range will be invalid.	Forcing Frequencies dialog box (Acoustics BEM)
5.	Define output requests.	Request the desired outputs In the Solution dialog box.Acoustical Mesh Results — Pressure, Normal Velocity, Normal Intensity.Microphone Results — Pressure, Velocity, IntensityAcoustic Power — Acoustic Power.Structural Results — Displacement, Velocity Acceleration and its Modal Contributions.	Request output for Direct Acoustic, Indirect Acoustic, and Indirect Vibro-Acoustic analysis types (Acoustics BEM)
6.	(Optional)Create an infinite plane, acoustic absorber, or transfer admittance simulation object.	Add other simulation objects to define the acoustical details of the simulation.	Boundary conditions (Acoustics BEM)
7.	Solve the solution process.		Solve the model
8.	Post-process the results.	Use Post-Processing Scenario to post-process the results by plotting function plots or contour plots of the acoustic results.	Scenario-based post-processing

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Solution formulation methods for indirect acoustic analysis (Acoustics BEM)

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