What is the "number of trial modes" in mode simulations?

What is the “number of trial modes” in mode simulations and how it affects the simulation?

“near n” searching option is chosen (default option)

The “number of trial modes” option means the number of modes that is going to be calculated by the solver and shown in the Mode list. The modes are listed in the order of their effective index (neff), i.e., the first mode has the largest neff, which is the fundamental mode. For example, if the “number of trial modes” is set to 20, the solver will try to find the first 20 eigenmodes supported by the structure, based on the parameters it is provided. Note that there could be less than the “number of trial modes” found, based on the settings it has, e.g., boundary conditions, mesh, etc. For more information about the Modal analysis tab, please refer to this link.

This is one of the settings that will allow you to find the mode(s) you want from the Mode list. The default setting is 20. If you don’t see the mode you want in the Mode list, you can choose to increase this value to find the modes again. Note that it is possible that there could be other parameters affecting the modes calculated in the Mode list. If you have trouble finding the mode you want and don’t mind sharing your file here, I am more than happy to take a look at it.

“in range” searching option is chosen

When n1 and n2 are defined, the solver will try to find all the modes within the range (n1, n2). It finds a set of modes near n, then sweeps n from n2 to n1. In each round, the “number of trial modes” define the number of modes that it will try to find near n. It means that a larger value of the “number of trial modes” will allow the solver to return more modes in each update. The solver will stop once all modes in the range of (n1,n2) are found.

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When I set “number of trial modes” to 4, the eigen solver kept finding modes even it had found and displayed more than 4 modes (I stopped it at 9). Is 20 is the minimum value?

The minimum for that value should be 1. If you do so, it should only return the first mode it can find and stop finding. What version of MODE you are using. If you dont mind, please also upload the simulation file here so that I can test it for you.

Dear kchow,
This is my layout file : kx_question.lms (78.3 KB)

I’m using version 7.8.982 on Windows 7 (64bit).

Thanks for following up and attaching the file. I ran the file, and it does return more than the number of trail modes like you said. The reason is that you have chosen the “in range” option, which will find all the modes for you. The “number of trail” mode here is the modes that it will find in each round. But it will still find all the modes for you. I will update my original reply at the top to clarify that.

Dear Kchow,
Thank you for the clear explanation.

Good morning!
It’s me again.
Can we restrict the number of total found modes (not the max number of modes near some n value) using script?
For example, " if-syntax" that stops and quit findmodes command.
I know that default maximum modes is 100, Mode Solutions will quit when it reaches this value, so what is the name of the corresponding variable?
Thank you!

Hello,

I was not sure if I understand the question. The findmodes command will find all the modes based on the parameter given. I am not aware of a way to stop the findmodes process half way. If you can tell me what is the situation here, I am happy to give more comments.

Hi Kchow,
After creating objects on the layout, I want Eigen mode solver to find modes in range say 1.55 to 1.45 (index). I want to it to stop automatically after it find out say 10 modes. Is it possible?
Sorry for the previous bad stated question.

Thanks for the clarification.

The “in range” option will return all the modes that fall within the index range that you specified, so it is not exactly what you are looking for. I guess the other thing you could try is to use “near n” with the “use max index” option unchecked. then put say 1.55 in the “n” field. If the “number of trial modes” is 10, then it will return the first 10 modes calculated started with an neff near 1.55. However, I am not aware of an option to strictly start the neff at 1.55.