Acoustic Demonstration.
Actran software is generally known for its ability to simulate acoustic problems. Using FE analysis, Actran can determine the sound radiating from a vibrating object based on the object’s structural analysis.
The acoustic radiation can be calculated within the frequency or time domain using various techniques, including Discontinuous Galerkin Method (DGM), infinite element and Adaptive Perfectly Match Layers (APML).
First, the structural analysis must be performed using Nastran, Adams/Flex or any other FEA analysis software. Actran even has its own structural analysis capabilities, if they will be sufficient for your analysis.
Acoustic infinite elements setup
To produce the acoustic simulation, the mesh must be constructed in three parts. First, the convex exterior mesh layer will contain the whole simulation. Within the exterior surface is the interior surface, a mesh that wraps around the object and serves as a map for these vibrations. Finally, the volume element will be contained between the aforementioned surfaces.
The structural vibration information is then mapped into the interior acoustic mesh. The Integration mapping technique is superior to standard sampling mapping. With integration mapping, your acoustic nodes will be optimized for your structural mesh’s vibration information. However, with standard sampling, information can be lost if there is a limited number of acoustic nodes on the structural mesh.
From here, various techniques can be used to produce the simulation including the infinite elements technique, where infinite elements are an extension of the acoustic finite element. The infinite elements will show up as a footprint on the finite analysis. However, this technique ensures that the waves do not reflect at the finite element/infinite element interface. This will provide accurate solutions and pressure fields past the actual finite element domain.
Acoustic PML setup.
When working with multiple frequencies, or when the PML has two opposing constraints, APML should be used. It is important that the PML layer be at the correct thickness to absorb the acoustic wave. This thickness will be dependant on the wavelength. For APML, the mesh is adapted for these varying frequencies for reducing computations and designing the problem.
The Discontinuous Galerkin Method (DGM) solves the simulation using linearized Euler equations. Therefore, the system is solved within the time domain, though frequency domain results are also produced. The solver is designed to calculate acoustic propagations over non-uniform or rotational flows. This means that larger models are calculable, like an aircraft engine’s turbofan containing 500 m3 of air propagating at 1200Hz. This is because the solver is scalable and thus is able to use hundreds of CPUs with low RAM dependence.
Once calculated, these simulation results can then be post processed into waterfalls, maps, acoustic directivity, animation, element contributions, time domain pressure or frequency response diagrams. Interestingly enough, the simulation can even be recorded into a sound file.
Source and Images courtesy of MSC Webinar: Solving Higher Frequency Acoustic Radiation Problems with Improved Efficiency
Resource: Simulatemore