# earthquake spectrum

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 August 4, 2011, 01:16 earthquake spectrum #1 Member   Hamed Join Date: Jun 2010 Posts: 43 Rep Power: 8 Hi all, I want to model a tank sloshing with respect to earthquake acceleration. How should I define the earthquake spectrum for ansys cfx? I'm doing mesh motion. Regards; hamed

 August 4, 2011, 18:40 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,714 Rep Power: 99 CFX cannot model in the frequency domain like modal analysis in FEA. You are going to have to convert it into a displacement versus time and impose that as a mesh motion.

 August 6, 2011, 09:32 #3 Member   Hamed Join Date: Jun 2010 Posts: 43 Rep Power: 8 Thanks for the reply. If I have a graph of displacment vs time, how should input that to cfx as the mesh displacement? best regards;

 August 7, 2011, 08:37 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,714 Rep Power: 99 Have a look at the tutorial examples for how to implement moving mesh.

 August 7, 2011, 09:48 #5 Member   Hamed Join Date: Jun 2010 Posts: 43 Rep Power: 8 Thanks. I know how to do mesh motion with a known equation. But know I have the graph of acceleration vs time. If I manage to integrate it and get the plot of displacement vs time, how can I give this as mesh motion. It is not an equation which I could simply enter for mesh motion displacement. Regards;

 August 7, 2011, 18:53 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,714 Rep Power: 99 If you have the equation of motion then why can't you use it?

 August 7, 2011, 20:11 #7 Member   Hamed Join Date: Jun 2010 Posts: 43 Rep Power: 8 No I don't have the equation. As I said I just have a graph of displacment vs time. I don't know how to implement this graph to mesh motion.

August 8, 2011, 04:24
#8
Member

Ali Torbaty
Join Date: Jul 2009
Location: Sydney, Australia
Posts: 72
Rep Power: 9
Quote:
 Originally Posted by enghamed No I don't have the equation. As I said I just have a graph of displacment vs time. I don't know how to implement this graph to mesh motion.

Create a text file from your data with X Y format, then import it into a CFX function.

 August 8, 2011, 08:08 #9 Member   Hamed Join Date: Jun 2010 Posts: 43 Rep Power: 8 Dear Ali, Can you please be more specific and guide me on this. How should I make the text file and then how can I input it in cfx? Thank you very much.

 August 8, 2011, 18:26 #10 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,714 Rep Power: 99 Use a 1D interpolation function. I set these up by generating the function with some dummy data then editting it in the command editor to include your data points.

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