## General Mechanical

#### Modal Info from Modal and Modal Acoustics

• Esteban_Guajardo
Subscriber

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

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

Regards Ashish Khemka
• Esteban_Guajardo
Subscriber

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?