Mesh
Maximum Frequency
The maximum frequency depends on the time step size 
. The maximal frequency 
is computed with 
, the Nyquist criterion.
. The maximal frequency is computed with , the Nyquist criterion. Mesh Criterion for an Acoustic Analysis
The mesh criterion is 5 (4-6) quadratic elements per wavelength. The wavelength is computed with 
, with c the speed of sound and 
the maximal frequency.
, with c the speed of sound and the maximal frequency. Shrinkwrap Mesh
The shrinkwrap mesh is the mesh surrounding the structure without sharing the nodes with the structural mesh. The shrinkwrap of the tuning fork (from the Getting Started Using Adams Acoustics tutorial) surrounds the fork entirely (grey surface), as shown:
Full Acoustic Mesh
A full acoustic mesh consists of:
1. Shrinkwrap (blue surface)
2. Finite acoustic mesh (brown 3D volume)
3. Infinite elements' 2D surface (pink surface) for far field radiation and the non-reflecting boundary condition.
Generating an Acoustic Mesh Manually
The primary Actran interface product, Actran VI, offers easy to use tools to create the shrinkwrap, the acoustic mesh and the infinite element surface. This includes the functions for filling holes, the exterior shrinkwrap, and ellipsoid and volume meshing. Please ask the Actran support, support@fft.be for further details.
Distance from Structure
The distance is not mandatory, if no distance is given, then the default value is used. Note that the typical distance values are 1-10 mm depending on the size of the acoustic mesh.
Fill Holes
In cases where the surface of the flexible body is not entirely closed, the shrinkwrap will not create a surface around the structure but will enter inside the opening. If the shrinkwrap enters in the structure, the result of the acoustic radiation will be wrong. Thus, this must be avoided. Therefore, the fill holes feature is automatically executed prior to the automatic meshing. The button "Edit" in the mesh tab opens Actran VI and loads the Shrinkwrap surface. This allows users to check whether the shrinkwrap enters in the flexible body. Please note that for the "Edit" button to work an Actran VI license is needed, an "Adams Entry License for Actran" is not sufficient.