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How to create Load recepie in Vibro acoustics analysis

Pioneer
Pioneer

Hi All,

 

I am trying to simulate a vibro acoustics problem in simcenter (attached a snapshot). The problem is as follows:

An audio speaker is placed in a box. The sound waves excite the box and are received finally by a array of microphones that are placed at a distance away from the box.

I am trying to do it in two parts: 1. Two way coupling vibro acoustics simulation of audio speaker and box to get the box displacement values at different forcing frequencies.

2. One way coupling of box and medium outside it upto the microphones array. I plan to use a load recepie having displacement of box at different forcing frequency data as excitation load for the structure in this part.

The thing that I can't figure out is how to create the load recepie to import in this simulation. Can anyone help me with it??

 

Also I would like like to get some feedback on the following:

1. Is it good to simulate audio speaker with a monopole??

2. SInce the fluid domain is too large in part 2, I plan to use AML, is there some rule to find the dimensions of AML to be used

3. Is there a better way to simulate this problem (like maybe doing it in one simulation)

 

Thanks,

Ashwani Thakur.Acoustics simcenter11.jpg

4 REPLIES

Re: How to create Load recepie in Vibro acoustics analysis

Siemens Valued Contributor Siemens Valued Contributor
Siemens Valued Contributor

Ashwani,

 

Your loads (structural displacements) are saved in what file format?  Currently Simcenter can only define load recipe using result file in the fllowing formats:

 

Ideas universal file UNV, Nastran Punch file, OP2 file, or test.lab lms file

 

Here are the steps to define laod recipe:

(a) In the simulation file, go to Properties -> Load Recipe,  import the file

(b) select the option "Automatically populate the mapping table...."  You should see a Load condition defined (in the Load Conditions tab)

 

V1.png

 

(c)  You can use the default "Automatic Entity (AE)" to map the structural displacements to the FEM nodes

 

v2.png

(d) Select the "Run Validate Check" to make sure all dispcements are mapped correctly to the structural FEM mesh

 

V3.png

 

For ypur questions:

(1) yes, you can model the speaker with monopole (Define Power for the Magnitude).  But you will not capture the sound directivity (i.e. the sound radiation pattern) correctly.

(2) the AM mesh must be convex, you just need to create a layer of acoustic solid elements away from the structural mesh.  You can use the meshing tools Convex mesh in simcenter to create this mesh

(3) This is a one way coupling problem (i.e. weak coupling, structural vibration already calculated and defined in Load recipe).  Just define a Vibro-Acoustic SOL 108 Direct Frequency Response for this analysis.

 

 

 

 

Re: How to create Load recepie in Vibro acoustics analysis

Pioneer
Pioneer

Hi,

Thank you so much for the response. It was really helpful.

 

However I am still unable to apply the displacement as an excitation load using load recepie. 

When I run validation check in load recepie, I get error saying "most of the load is missing for the target entity" (attached error 1 snapshot).

Then I though maybe it was due to different node numbering between op2 file and my structural mesh, then I used same mesh and node numbers but still it says 74 % of load is missing target entity (attached snapahot 2). I tried using the append option also, therefore appending the fluid mesh onto structural mesh with same node id's as in my op2 file but also didn't work.

Can you please troubleshoot this problem.

If I run simulation ignoring this message, I get erro message in results as " This frequency response analysis has no excitation specified for it".

 

Thank you,

Ashwani Thakur.

Re: How to create Load recepie in Vibro acoustics analysis

Siemens Valued Contributor Siemens Valued Contributor
Siemens Valued Contributor

Your op2 file and structural mesh should have the same Node ID numbers.  The 74% of load is missing is normal.  You have structural mesh and acoustic mesh, the loads only mapped to the structural mesh and not on the acoustic mesh.

 

For the next error; you can edit the solution, and define frequencies, make sure you "add" frequency to the list.

 

vv1.png

 

vv2.png

Re: How to create Load recepie in Vibro acoustics analysis

Pioneer
Pioneer

Hi, Thanks for the reply.

My node id's in the op2 file is same as that in my structural mesh. Also, I have defined the forcing frequencies. 

Also, I checked the deformation values in op2 file, it is good enough and not nearly zero. 

But still, when I run the solution, I get the error as below"

This frequency response has no excitation specified to it. Applied load and enforced motion are both null"

I have attached the snapshots of the error message, excitation frequencies and load recipe. 

I am unable to crack down what am I doing wrong?

 

Thanks,

Ashwani Thakur.