FSI- Negative Pressure

ashtonJ · December 2, 2014, 01:07

Dear all,
I am doing FSI modelling in an artery. I find the deformation of the artery wall a bit strange and non-physical. The fluid pressure waveform at the inlet of the model is attached here.
The artery wall gets expanded when the fluid pressure is positive and then it gets compressed when the fluid pressure is negative.
I am completely confused why the artery wall gets compressed when the fluid pressure is negative? Is this behavior physical?

Thanks for your help.
AshtonJ

ghorrocks · December 2, 2014, 01:52

This can happen if you have inertial effects, either in the fluid or the vessel wall.

ashtonJ · December 2, 2014, 02:31

Thanks Glenn.
So, if the compression is due to the inertia force, then it should only happen in 2 way FSI, not one way FSI because in one-way FSI, only fluid pressure is transferred to the wall, am I correct?

In addition, based on my results the amount of the vessel compression is approximately same as the amount of the vessel expansion. Should the expansion percentage be greater than the compression percentage?

ghorrocks · December 2, 2014, 18:45

Yes, if the wall has mass/inertia than you need two way FSI to get that to affect the flow.

Also I note your initial post says "I am completely confused why the artery wall gets compressed when the fluid pressure is negative? Is this behavior physical?" - isn't it the expected behaviour that the wall compresses when the fluid pressure is negative?

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December 2, 2014, 01:52		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	This can happen if you have inertial effects, either in the fluid or the vessel wall.

December 2, 2014, 02:31		#3
ashtonJ Senior Member Ashkan Javadzadegan Join Date: Sep 2010 Posts: 255 Rep Power: 17	Thanks Glenn. So, if the compression is due to the inertia force, then it should only happen in 2 way FSI, not one way FSI because in one-way FSI, only fluid pressure is transferred to the wall, am I correct? In addition, based on my results the amount of the vessel compression is approximately same as the amount of the vessel expansion. Should the expansion percentage be greater than the compression percentage?

December 2, 2014, 18:45		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	Yes, if the wall has mass/inertia than you need two way FSI to get that to affect the flow. Also I note your initial post says "I am completely confused why the artery wall gets compressed when the fluid pressure is negative? Is this behavior physical?" - isn't it the expected behaviour that the wall compresses when the fluid pressure is negative?