General Mechanical

General Mechanical

Modal Info from Modal and Modal Acoustics

    • Esteban_Guajardo

      Hi @wrbulat , Hi @akhemka

      I saw some of your post... they are really helpful. Thanks for that.

      I have some questions, I hope you can help me:

      • I have been working on some tanks models with the "Modal" module. I have been collecting good results regarding the modes of the convective mass (within the order of 0.1 to 0.3 Hz), but I have not been lucky in terms of the modal information associated with the impulsive mass. The number of modes that I ask the program for is a bit exaggerated (more than 5000 modes and still don't get the impulsive modes), so I would like to know if there is any possibility to limit this number of modes, i.e. that the program only calculates the modes in one direction only, since a cylindrical tank fortunately has symmetry. I know that I get to specify the number of modes, but the problem is that I get the modes (or frequencies) in pairs, and the difference between them are really tiny (up to the fourth decimal). The impulsive mass of tanks normaly (depending on the dimensions of the tank) will be activated at the higher frencuencies, and because of these differences in them, that I've talked you about, the number of modes that I have to ask is really "a bit much" and still can not get the information for the impulsive frecuencies. I dont know if one can manipulate the tolerances of the decimals in order to reach "engineering results"...maybe truncate decimals to second digit, I think is a reasonable way to go. You can see in the image how many 0,75 Hz the program calculates, which is completely useless under my humble point of view.
    • Ashish Khemka
      Ansys Employee

      Please see if the following link helps you:

      Mode Participation Factor and Effective Mass ÔÇö Lesson 4 - ANSYS Innovation Courses

      Regards Ashish Khemka
    • Esteban_Guajardo

      Thanks for your answer.
      Unfortunately, for Modal Acoustics the are just the participation ratio and a ratio shown, which these do not have any relation with the modal masses or any other calculation. The possibility that I'm completely wrong is also there... XD
      Could I send you one of my models so we can talk about it?
      Thanks in advance
    • KrishnenduP

      Hope you are well.
      Have you got a solution to determine the modal mass values for each mode frequency using Modal acoustics simulation? Please let me know. When I study the mode shapes with modal analysis, the output solution file itself gives the corresponding modal mass values for each mode. However, same doesn't happen while using modal acoustics. I tried to use the relation with kinetic energy and modal mass, but the results are not matching. Please help me solve this if you have got a solution to your problem.
      Thank you Best Krishna

    • FRCL
      Hello, I have a question regarding Modal and Modal Acustics, what is the difference between the two studies?
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