Vortex-Induced Vibration Simulation

jack.callaghan · February 15, 2016, 09:49

Hi all,

For a project at University I am working on modelling vortex-induced vibrations of a pivoted cylinder in a water flow channel. So far I have determined three possible methods for doing this:

Fluent / Transient Mechanical System Coupling
Fluent Rigid Body Dynamic Mesh
CFX Immersed Solid w/ Rigid Body Dynamics

I am having different problems with all three.
For (1) the solution is very labour intensive, and I do not have access to higher computing power.
For (2) the dynamic mesh often distorts to a degree that the mesh is no longer an accurate representation of the domain.
For (3) the motion of the cylinder often leaves the fluid domain, which in reality is impossible.

I am not looking for a definitive solution to this problem, but ask for advice from those who have tried similar simulations with what I might try to accurately model this system.

Regards,
Jack Callaghan

Reeb · February 16, 2016, 14:19

Hi Jack,

Have you tried doing a FSI simulation using CFX? I did a project for 2,5 years ago and I think that it worked better than FSI with Fluent. If I remember correctly it was not straight forward to get it to work but eventually it worked.

Have you tried any other software that is easier to setup when it comes to FSI simulations? I have used LS-DYNA and when the fluid and structural parts are defined the FSI coupling is activated with one simple command. Their probably exist other similar solvers also but non that I can the name of.

Best regards,
Marcus Timgren

jack.callaghan · February 17, 2016, 07:42

Hi Marcus,

Thanks for the reply.
Correct me if I am wrong but I think method 3 I defined is using FSI in CFX.
Do you know of any tutorial for the method you used so I might compare and see if I am doing anything wrong?

I do not have access to any other CFD software than ANSYS Mechanical, Fluent, and CFX.

Regards,
Jack Callaghan

Reeb · February 18, 2016, 02:46

Hi Jack,

If I have understood you correctly, you do not couple the CFX to ansys mechanical? If I remember correctly I use an approach similar to this https://youtu.be/jNjYuw9mznA.

Also take a look at look at chapter 5 in the following guide, it contains some good advice on how a 2-way FSI simulation is setup. http://148.204.81.206/Ansys/150/ANSY...ce%20Guide.pdf

I hope that this will help you.

Best regards,
Marcus

February 15, 2016, 09:49	Vortex-Induced Vibration Simulation	#1
jack.callaghan New Member Jack Callaghan Join Date: Oct 2015 Posts: 2 Rep Power: 0	Hi all, For a project at University I am working on modelling vortex-induced vibrations of a pivoted cylinder in a water flow channel. So far I have determined three possible methods for doing this: Fluent / Transient Mechanical System Coupling Fluent Rigid Body Dynamic Mesh CFX Immersed Solid w/ Rigid Body Dynamics I am having different problems with all three. For (1) the solution is very labour intensive, and I do not have access to higher computing power. For (2) the dynamic mesh often distorts to a degree that the mesh is no longer an accurate representation of the domain. For (3) the motion of the cylinder often leaves the fluid domain, which in reality is impossible. I am not looking for a definitive solution to this problem, but ask for advice from those who have tried similar simulations with what I might try to accurately model this system. Regards, Jack Callaghan

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February 16, 2016, 14:19		#2
Reeb New Member Marcus Timgren Join Date: Feb 2016 Location: Sweden Posts: 11 Rep Power: 10	Hi Jack, Have you tried doing a FSI simulation using CFX? I did a project for 2,5 years ago and I think that it worked better than FSI with Fluent. If I remember correctly it was not straight forward to get it to work but eventually it worked. Have you tried any other software that is easier to setup when it comes to FSI simulations? I have used LS-DYNA and when the fluid and structural parts are defined the FSI coupling is activated with one simple command. Their probably exist other similar solvers also but non that I can the name of. Best regards, Marcus Timgren

February 17, 2016, 07:42		#3
jack.callaghan New Member Jack Callaghan Join Date: Oct 2015 Posts: 2 Rep Power: 0	Hi Marcus, Thanks for the reply. Correct me if I am wrong but I think method 3 I defined is using FSI in CFX. Do you know of any tutorial for the method you used so I might compare and see if I am doing anything wrong? I do not have access to any other CFD software than ANSYS Mechanical, Fluent, and CFX. Regards, Jack Callaghan

February 18, 2016, 02:46		#4
Reeb New Member Marcus Timgren Join Date: Feb 2016 Location: Sweden Posts: 11 Rep Power: 10	Hi Jack, If I have understood you correctly, you do not couple the CFX to ansys mechanical? If I remember correctly I use an approach similar to this https://youtu.be/jNjYuw9mznA. Also take a look at look at chapter 5 in the following guide, it contains some good advice on how a 2-way FSI simulation is setup. http://148.204.81.206/Ansys/150/ANSY...ce%20Guide.pdf I hope that this will help you. Best regards, Marcus