Modal analysis -reduced -fluid80

In summary, the conversation is about modeling a tank filled with water for modal analysis in ANSYS using fluid80 for the fluid and shell 63 for the tank. The reduced method was used due to it being the only acceptable method, but the mass values in each direction are much higher than the total mass. The units are consistent and the mass calculated by ANSYS is correct. The person suggests posting to XANSYS for help and checking ACEL for any issues. Another person working on a similar problem also shares their experience and asks for help in finding a solution.
  • #1
rengg
1
0
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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  • #2
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.
 
  • #3
@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 theoritical 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.
 

1. What is modal analysis?

Modal analysis is a technique used in structural engineering and mechanical engineering to determine the natural frequencies, mode shapes, and damping ratios of a system. It is used to understand the dynamic behavior of a structure or system under different loading conditions.

2. How is modal analysis performed?

Modal analysis is typically performed through experimental testing or numerical simulation. In experimental testing, the structure is excited at different frequencies and the response is measured. In numerical simulation, a mathematical model of the structure is created and analyzed using specialized software.

3. What is reduced modal analysis?

Reduced modal analysis is a technique used to simplify the modal analysis process by reducing the number of modes that need to be considered. This is typically done by removing modes that have a low contribution to the overall response of the system.

4. What is fluid-structure interaction in modal analysis?

Fluid-structure interaction is the term used to describe the interaction between a fluid and a solid structure. In modal analysis, this refers to the dynamic response of a structure due to the interaction with a surrounding fluid, such as air or water.

5. What is the significance of fluid80 in modal analysis?

Fluid80 is a type of fluid element used in numerical simulations for fluid-structure interaction in modal analysis. It is a commonly used element type that is based on the Navier-Stokes equations and can accurately model the behavior of fluids in a system.

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