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Subject: Re: [PHYS] MFX fluid-structure interaction issues
Author: Molly Rice
Date: 2008-04-26 16:06:39

Anup,

Thanks for your reply. I understood and have already tried everything you
mentioned, but I think my problem is in the particulars. In the CFX
simulation set up, if I choose the MultiField using Prep7, it asks for an
input file. What exactly should be contained in that .inp file -
displacements of the boundary? time conditions? or just the interface
information? And should the solver time controls (MFTIME/MFRS) be identical
to the load step timing conditions?

I feel like these may be simple questions, and I apologise for that. This
is my first foray into CFX, I am really only familiar with Ansys classic
thermal & structural analysis. I've very rarely used Workbench, so I am
reluctant to try to learn that platform as well.

Again, thank you,
Molly
*

Author: *Anup Paul
*Date: *2008-04-25 17:142008-04-25 16:14 +100UTC
*To: *'ANSYS User Discussion List'
*Subject: *Re: [Xansys] [PHYS] MFX fluid-structure interaction issues
Molly,

- The simulation has to a full transient analysis, i.e. no modal or harmonic

simulations allowed
- the displacement load for a vibrating plate would have to be given as a
transient displacement history in Ansys. If you are using workbench 11.0,
you can define this as an expression or a table. The displacements loads
will be defined in the .dat or .inp file.
- in CFX, the corresponding boundary should be defined as a moving boundary,

with the displacements set to the Multi-field option
- the coupling between the two codes are defined in Ansys (using MF
commands) and in CFX-Pre, where you link the corresponding FSIN's &
interface names.
- the solver controls including time step controls are all set in the Ansys
.dat or .inp file, using MF commands.

In 11.0 you can do all the above in workbench, between the simulation tab &
the adv. Cfd tab. Look at tutorial 21 in the CFX Tutorial manual.

Anup Paul
www.stress.com

This message is not provided as a Stress Engineering employee.




-----Original Message-----
From: xansys-bounces_at_??? [mailto:xansys-bounces_at_???] On Behalf
Of Molly Rice
Sent: Friday, April 25, 2008 11:47 AM
To: xansys_at_???
Subject: [Xansys] [PHYS] MFX fluid-structure interaction issues

Hello all,

I have been desperately attempting to model an "easy" fluid-structure
interaction involving a vibrating plate. Ideally, the motion of the plate
would be derived from a straight-forward modal analysis of the first five
modes.

That said, I've hit a significant stumbling-block: I cannot figure out how
to transfer the displacement loads from the structural to CFX. As it seems
that the modal displacements won't translate directly into CFX, I've instead

modelled the displacement as a set of load steps, which works fine on the
structural side. But how is that translated over to CFX? I have set up the
necessary interface information (FSIN numbers and interface names, etc), but

as it is a transient analysis, the loads cannot be applied all in one go.
I've tried MFRS commands, to stop the analysis and restart under new loading

conditions, but that hasn't seemed to work.

So, I suppose my question is where is the loading information inputted? In
the input file inserted in the CFX simulation information? Or is that
written into the .dat file? I've tried the MFX tutorial, but it's not
terribly informative. Does anyone have access to a tutorial that explains
the entire process through, instead of running batch runs on input files?

General information: I'm running Ansys and CFX 11.0, both with SP1
installed, on a Teaching (university) license. The operating system is
Windows XP x64

I hope that this question is coherent. Thank you for anyone's input and
time, and Happy Friday!

Molly Rice
Graduate Student, MSc ME
University College London
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Posts possibly associated with message #93045AuthorDateScore
93020[PHYS] MFX fluid-structure interaction issuesMolly Rice 2008/04/25 
93021Re: [PHYS] MFX fluid-structure interaction issuesAnup Paul2008/04/25 
93045Re: [PHYS] MFX fluid-structure interaction issuesMolly Rice 2008/04/26 
93074Re: [PHYS] MFX fluid-structure interaction issuesAnup Paul2008/04/28