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Subject: Re: Ansys FSI nightmare
Author: Victor Salit
Date: 2008-04-28 08:04:27Tan,
I'm not an expert on buckling related problems, but I do have a few
comments:
> Anyway to think about it from a wider perspective, my objective of this
> test
> was to check and see if Ansys could model this problem and right now,
What is the title of your work? What you have stated above just can't be an
objective of any serious work. Think about it - if you have any success, you
can conclude that it is possible to do it. If you have no success - you
can't conclude anything about the tool, it most probably your lack of
experience (unless your name is Christopher Wright).
> for this. So it would be very helpful if some of you could help me
> answer a few
> questions:
Be careful - people here will probably help you with physics and Ansys, but
don't expect them to help you with the writing...
> Peter, I have this feeling too that it might be a dynamic problem but
It can be dynamic and/or quasi-static depending on some parameters.
Have you done the literature survey? There are people who have done a lot of
research on buckling (including experimental) of long pipes under external
pressure. Look for papers of Stelios Kyriakides for example (google). There
is a nice summary of the topic in the chapter 18 of the book "Buckling
Experiments"
http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0471974501.html
> of the literiture mention that with those b.c's oscillations would not
> occur.
...
> Christopher, I am testing my results against a published literiture, I
Can you cite this literature?
> 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
...
> Anup, the aim of my exercise is to develop a model for blood flow inside
> a vein and the physics of the vein is exactly similar to flow inside a
flexible tube.
While thin-walled metallic (and made from some other materials) pipes will
buckle under external pressure, pipes made from 'soft' rubber-like materials
will just deform, even if the final shape (sometimes) will be similar.
Buckling is a loss of stability. Can you imagine blood vessels collapsing
due to a local (finger indent), or global (diving) pressure??? Do you really
understand the physics of the vein? And what constitutive law do you use for
vein walls?
Regards and good luck,
Victor Salit
===========================================
Victor Salit, M.Sc.
Division of solid Mechanics
Department of Civil Engineering & Geodesy
Technical University Darmstadt
Hochschulstrasse 1
64289