Visualizing Acoustic Mode Shapes and Acoustic Frequencies

You create a scalar scene and plots to display acoustic mode shapes and frequencies within the cylindrical burner geometry.

To visualize acoustic mode shapes and acoustic frequencies:
  1. Create a scalar scene and rename it Acoustic Pressure Normalized.
  2. Edit the Scenes > Acoustic Pressure Normalized > Scalar 1 node and set the following properties:
    NodePropertySetting
    Scalar 1RepresentationAcoustic Modes View
    PartsPartsDerived Parts > [midplane]
    Scalar FieldFunctionAcoustic Pressure Normalized
  3. Select the Solution Views > Acoustic Modes View node and edit the value for Acoustic Mode from 1 through 6.
    The image in the Acoustic Pressure Normalized scalar scene displays the normalized acoustic pressure for each of the 6 acoustic modes on the midplane part (the acoustic pressure is scaled from 0–1). The following images show modes 1-6 :
    Mode 1:

    Mode 2:

    Mode 3:

    Mode 4:

    Mode 5:

    Mode 6:

    The results highlight that the mode shapes are longitudinal, that is, the nodes are located axially along the length of the domain.

  4. Create a plot to display the normalized acoustic pressure through the axial centreline of the cylindrical burner.
    1. Right-click the Plots node and select New Plot > XY Plot.
    2. Rename the Plots > XY Plot 1 node to Centreline Mode Shape.
    3. Expand the Centreline Mode Shape node and set the following properties:
      NodePropertySetting
      Centreline Mode ShapeTitleMode Shape
      PartsDerived Parts > [center line]
      RepresentationAcoustic Modes View
      X Type
      Vector QuantityValue[0.0, 0.0, 1.0]
      Y Types
      Y Type 1 > Scalar FunctionField FunctionAcoustic Pressure Normalized
  5. Select the Solution Views > Acoustic Modes View node and edit the value for Acoustic Mode from 1 through 6.
    The Centreline Mode Shape plot updates to display each of the six acoustic mode shapes on the centreline part. The following image shows an example of the centreline mode shape for mode 6, which emphasizes the varying amplitude and frequency for this mode. The growth rate for this mode is positive, as observed from Acoustic Frequency Table results, hence the pressure fluctuations are expected to grow with time—and the mode is unstable.


  6. Save the simulation.