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Mfluid element mass repartition :OS-V: 0460 Dynamic Behavior of a Fluid-containing Structure using MFLUID

I have been using the benchmark model appearing in your guide for some simulations.

OS-V: 0460 Dynamic Behavior of a Fluid-containing Structure using MFLUID
However there are some points that I would like to clarify with your support on these models to get a better understanding of the Mfluid element available on your package.

My question is regarding the Mass matrix outpu.Indeed when we simulated we observed that the mass is lower in the Z direction than the 2 other directions, even when you have a 100% fill.
How is this possible? Is there any theoretical explanation for this ?

Thanking you in advance

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OptiStruct

v2020.1

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Xiaolei

Hi Insaf,

Can you let me now how you checked the mass matrix of virtual mass alone? As long as I know OS only supports DMIG for the entire model(structure+MFLUID).

Can you also check partial filled let's say with a height that is smaller than radius of the cylinder?

Thanks.

Xiaolei

Insaf Mohamed Rizan

Hi Insaf,

Can you let me now how you checked the mass matrix of virtual mass alone? As long as I know OS only supports DMIG for the entire model(structure+MFLUID).

Can you also check partial filled let's say with a height that is smaller than radius of the cylinder?

Thanks.

Xiaolei

Hello Xiaolei ,
You can add the following params to get the fluid mass matrix output:

PARAM,CHECKEL,NO
PARAM,EFFMAS,YES
PARAM,GRDPNT,15969
PARAM,VMMASS,YES
PARAM,VMOPT,1

I have tried for different fill levels and you get the result in the output file

Xiaolei

Hello Xiaolei ,
You can add the following params to get the fluid mass matrix output:

PARAM,CHECKEL,NO
PARAM,EFFMAS,YES
PARAM,GRDPNT,15969
PARAM,VMMASS,YES
PARAM,VMOPT,1

I have tried for different fill levels and you get the result in the output file

I tried with a 25% fill level(the one on the right side), then the pass in P1 and P2 is much smaller.

I don't have the formula of this directional mass calculation at hand, but I think this change should make sense.

Community-Pasted-Attachment-1707939860596.png