Modal analysis -reduced -fluid80

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SUMMARY

The discussion centers on performing modal analysis of a water-filled tank using ANSYS, specifically employing the Fluid80 element for fluid modeling and Shell63 for the tank structure. The users report encountering unexpectedly high mass participation values in each direction, despite consistent unit measurements and correct mass calculations by ANSYS. Suggestions include verifying the acceleration (ACEL) settings and considering the selection of master nodes, which may influence the excited mass results.

PREREQUISITES
  • Understanding of ANSYS software, specifically versions that support Fluid80 and Shell63 elements.
  • Knowledge of modal analysis principles and mass participation factors.
  • Familiarity with fluid-structure interaction concepts in engineering simulations.
  • Experience with setting up and interpreting results from finite element analysis (FEA).
NEXT STEPS
  • Investigate the impact of master node selection on modal analysis results in ANSYS.
  • Learn how to adjust and verify acceleration (ACEL) settings in ANSYS simulations.
  • Explore best practices for modeling fluid-structure interactions in ANSYS.
  • Research case studies on modal analysis of liquid storage tanks to compare methodologies and results.
USEFUL FOR

Engineers and researchers involved in structural analysis, particularly those focusing on fluid-structure interactions and modal analysis using ANSYS software.

rengg
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Hi,
i have been modeling tank filled with water for modal analysis in ansys.
fluid is modeled by fluid80 and tank by shell 63.
i have used reduced method as it is the only acceptable method.
i am getting very high values for mass participating in each direction which is much greater than the total mass.

units are consistent.
the mass calculated by ansys comes out to be correct

please suggest any thing that i may be missing.

regards
ritu
 
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I was going to suggest that you post to XANSYS, but I see that you already have. I would wait for the guys over there to help you out. I could have sworn that I've seen a post about that.

I know that you said your units are consistent, but if I had to stab, the only thing I could think of was checking your ACEL.
 
@rengg
i'm working on the same problem you see, it's my thesis "fluid structure interaction in liquid storage tanks for base excitation using ANSYS"
so far i too got same problem but if we only model fluid alone and give constraints then the excited mass matches to the theoretical one. The mass excited is more has a reason in selecting the master nodes you see, to which even I'm stuck. but in any way if you'd find the solution to it please it's my hmble request that share the information with me too..
Thanks in anticipation,
Sagar.
 

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