# Explicit dynamics - water tank sloshing due to earthquake

Member Posts: 14
edited December 2020

figures consist of a rectangular tank consisting of water, and acceleration vs time data

I have earthquake load as acceleration vs time data. I need to give acceleration to the bottom face of the tank only. But It is not possible in explicit dynamics since it can only be given to "All Bodies" as you can see in the figure.

1. Does anybody know how to give acceleration vs time data to the tank base in explicit dynamics? or
2. Since providing displacement to the tank bottom face in explicit dynamics is possible, (for acceleration only "all bodies" is possible) does anyone can convert the acceleration vs time data, to displacement vs time data and send me or/ and if possible include the MATLAB is used send the code too? (excel is not attached as attachments are not possible here)

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## Best Answers

• edited December 2020 Accepted Answer

Attached is a zip file of the NS acceleration data double integrated to displacement in mm.

• Accepted Answer

The displacement at T = 0 must be 0.

• Accepted Answer

Analog signals exhibit offset and drift, which must be corrected in the data.

Offsets are corrected by subtracting the mean from the data.

Drifts are corrected by subtracting the least squares line from the data.

You can do nothing, offset, drift or both before each integration.

There are two integrations, so there are 8 choices, and then you can make four more choices after the second integration.

That is what the vibrationdata GUI makes easy to try out different combinations to get the best result, which is generally that the displacement at the beginning and end of the seismic event is zero.

I did that, but I forgot to type a zero in for the displacement at T=0 in the zip file I gave you. I forgot that Explicit Dynamics chokes on a non-zero value. A different strategy is to use the velocity data as the input to the simulation, because you are allowed to have a nonzero velocity at T=0.

## Answers

• Acceleration can only be applied to All Bodies.

You can apply Displacement or Velocity to the base of the tank.

You can attached a zip file to posts. Put the Excel file inside a zip file.

I can convert your data with matlab, or you can download the free GUI app I use in matlab called vibrationdata.

https://vibrationdata.wordpress.com/

• Hi Peteroznewman,

I am attaching accel vs time data as a zipped file, can you please convert it and send. This is a great help. Thanks in advance.

• Thanks a lot for your reply. It answered my question. Since I am still curious, can you send me the zip file of the matlab code you used to convert accel data to displacement?

• download the free GUI app I use in matlab called vibrationdata.

https://vibrationdata.wordpress.com/

• When I run the model by giving EQ load as displacements, following errors pop ups. Any reason You can mention?

I have used lagrangian for water tank and eulerian for water. I fixxed the bottom face and gave displacements. Errors pops up. Then I removed the fixed bottom face and gave displacements. Same errors pops up. Can you mention how to fix it? Thanks for the help. model attached.

• I used seismosignal software to convert the acceleration data to displacement data as I could not implement matlab code. It gives me different displacement data compared to your displacement data which provided in the previous zipped file. Can you settle this. Please can you tell me how you did the matlab coding and it would be great help if you could send it to me as I need to clarify it. It would be a great help.

As you can see in the figure highest displacement is around 2500mm.

• Thanks a lot for the reply. Can you integrate accel data to velocity data using Matlab code, since now I am trying to compare the velocity results of matlab and seismosignal software. Please can you send me the velocity vs time data.

• How to assign fluid properities mate?

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