Running the Acoustic Modal Analysis

Simcenter STAR-CCM+ Acoustic Modal Analysis solver computes the acoustic frequencies, normalized mode shapes, and linear growth rates for the cylindrical burner. The solver computes the non-reacting acoustic modes first, followed by the reacting modes using the n-tau model.

To run the acoustic modal analysis:

  1. Right-click the Solvers > Acoustic Modal Solver node and select Solve for Acoustic Modes.
    Progress is displayed in the bar above the Properties window.


  2. When the acoustic modal analysis is complete, save the simulation.
In the Output window, you can see the results of the computation.


The first table shows the acoustic modes of the non-reacting computation. This table does not provide any information on the growth rates. The second table shows the results obtained with the N-Tau model to describe the flame transfer function. These results include the stability information for each of the modes based on the growth rate. It is also possible to tabulate the second table by using the Acoustic Frequency Table option.
  1. To view the computed frequencies and growth rates, right-click the Continua > Physics 1 > Models > Acoustic Modal Analysis > Acoustic Frequency Table node and select Tabulate.



    Modes five and six display a positive growth rate which indicates that the pressure waves and heat release waves are in synchronization with each other, which causes instabilities to grow, and therefore these modes are unstable.

  2. Save the simulation.