Skip to content

Sound Barrier

Here we will perform a 2D simulations concerning wave propagation over a sound barrier.

Thereby the wave is excited by a point source on the right side of the barrier in the origin [x,y,z]=(0,0,0) of the domain.

For the analysis type, we chose a harmonic analysis in the frequency range of 34Hz to 680Hz with 10 linearly spaced samples.

Since we cannot create an infinitely large computational domain, we have to impose a model of free-radiation, in this example, we are using the PML (Perfectly Matched Layer) technique, described here.

acoustic


Meshing

As a preprocessor we use the free available software gmsh

The gmsh file is provided here and the mesh can be generated by executing

gmsh geometry.geo -2 -v 0 -format msh2 -o geometry.msh


XML Simulation Setup

The ready-to-use xml file is provided here as well as the material xml file.

Here, we will just discuss the main parts of the XML description file (for a deeper introduction into the different analysis types, we refer to the Cantilever example)

  • Domains with regions

    <domain geometryType="plane">
      <regionList>
        <region material="air" name="prop"/>
        <region material="air" name="plate"/>
        <region material="air" name="pml"/>
      </regionList>
      <nodeList>
        <nodes name="excite">
          <coord x="0.0" y="0.0" z="0.0"/>
        </nodes>
      </nodeList>
    </domain>
    

  • Start the sequence and define analysis

    <sequenceStep>
      <analysis>
        <harmonic>
          <numFreq> 10 </numFreq>
          <startFreq> 34 </startFreq>
          <stopFreq> 680 </stopFreq>
          <sampling>linear</sampling>
        </harmonic>
      </analysis>
    

  • Define PDE for acoustics

      <pdeList>
        <acoustic>
          <regionList>
            <region name="prop"/>
            <region name="pml" dampingId="myPml"/>
          </regionList>
    

  • Define the PML (Perfectly Matched Layer) used for free field radiation

         <dampingList>
          <pml id="myPml">
            <type> inverseDist </type>
            <dampFactor>1.0</dampFactor>
          </pml>
        </dampingList>
    

  • Define excitation and output result

        <bcsAndLoads>
          <pressure value="1" name="excite"/>
        </bcsAndLoads>
       <storeResults>
          <nodeResult type="acouPressure">
            <allRegions/>
          </nodeResult>
        </storeResults>
    

Perform the openCFS simulation by executing

cfs simulation

Result

You can now investigate the results in paraview

result