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Subject: Re: Ansys FSI nightmare
Author: Mason Pillow
Date: 2008-04-25 20:50:44>From your description of how you executed the problem it sounds like you did
a single pass from CFD to FE. From your problem statement it looks like a
coupled field analysis is required.
I have one suggestion. You should start with an extremely simple coupled
field problem to get a validated process, then build up in a couple of
stages to your final model.
Regards,
Mason Pillow
Rolls-Royce
Mt. Vernon
-----Original Message-----
From: xansys-bounces_at_xansys.org [mailto:xansys-bounces_at_xansys.org] On Behalf
Of Christopher Astefanous
Sent: Friday, April 25, 2008 4:45 PM
To: ANSYS User Discussion List
Subject: Re: [Xansys] Ansys FSI nightmare
Tan,
I have no answers for you, but I can't help but comment. First off, where is
your dissertation advisor on this? (Is this for PhD or
Masters?)
If you don't get your dissertation in by the deadline, you have next
semester to do it, don't you? Hopefully, that's the case. You can relax,
it'll be a big pain but it won't be the end of life.
Secondly, with 1 week to go you now ask can ANSYS even solve this type of
problem? Have you tried breaking apart the problem iteratively? Like I said
before I have no answers for you as I have not worked with CFD.
Yet, can you manually iterate the coupled problem, i.e., Solve for the
geometry, set your geometry as fixed, solve for the flow field and internal
pressure, apply the pressure, resolve for the geometry. Instead of trying to
have ANSYS solve the coupling on its own. It sounds like the degree of
non-linearity is very difficult to over come since the buckled shape will
continually change as the internal pressure/flow field changes in a flexible
pipe.
Confused,
Christopher Astefanous
Frequency Electronics
-----Original Message-----
From: xansys-bounces_at_xansys.org [mailto:xansys-bounces_at_xansys.org] On Behalf
Of Y Y Tan
Sent: Friday, April 25, 2008 4:30 PM
To: xansys_at_xansys.org
Subject: [Xansys] Ansys FSI nightmare
Hi guys,
Its now 1 week away from my dissertation deadline, I have posted up my
problem several times and people here have helped me clarify alot of things.
Yet, I
still can not get the results that I want, I really feel that my FE skills
are letting me down or maybe its just how i approach things. I have ran my
FE model for almost 300 times now for the past few months and I have really
ran out of ideas what I can do.
Let me just explain my model again, I have a circular pipe, with a steady
state laminar flow through it. The pipe walls are flexible and an external
pressure is applied onto the pipe walls. Because the external pressure is
greater than the internal pressure of the fluid, the pipe will buckle
inwards and because of that, the flow will have to squeeze through the
constriction and the local pressure will drop because of Bernoulli, and as a
result the pipe will further deform. This is a highly non-linear and highly
coupled problem.
My question is, can Ansys actually solve this type of problem? I am
currently using MFX and doing the sequential analysis where I run CFX first
before I run Ansys. Would a simultaneous analysis be a better option?
I'm about to burst out in tears as I write this post, I really really hope
that someone here could understand the situation which I'm going through and
help me go through this modelling problem and consequently help save me from
failing my degree. :(
Regards,
Tan Yi Yong
The University of Sheffield
E: mea05yyt_at_sheffield.ac.uk
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