VIV simulation using FLUENT

Sopho · February 20, 2018, 15:11

Hello guys,

I am a 4th year engineering student and i'm trying to simulate Vortex Induced Vibration around a cylinder using Fluent, for my diploma thesis. I have read many papers so as to get a good understanding on phenomena and the physics that get involved in, and now i have turned to modelling this phenomenon in Fluent.

Before i begin with the simulations of a moving cylinder, i did some simulations of a stationary cylinder. The domain in these simulations was full of water (only water). The results were good and reasonable according to bibliography.

Now i want to move on to the next step, and my final goal is to simulate viv around cylinder inside a tank with water and air. Thus, i want to perform a simulation using VOF and Open Channel Flow. But i have some questions..

1) Which turbulence model is the best for this phenomenon.
2) How can i model hydrostatic pressure? In the region of air the pressure is atmospheric, since it is an free surface, but as you go deeper in the tank the pressure is increasing and is equal to Patm+ρ*g*h. Maybe i could do this, by using a UDF but i don't know how to write this particular UDF. Is there any other possible way to model hydrostatic pressure. I would appreciate if someone shared a similar udf.

Far · February 21, 2018, 00:40

Yes this can be done on Fluent. And it is pretty common simulation people are doing. You can find the UDF for 6 DOF on net or even in Fluent UDF manual.

Far · February 21, 2018, 00:44

You can also go through many videos on youtube

This was done in fluent

https://www.youtube.com/watch?v=_VLUbhNz6Dk"]https://www.youtube.com/watch?v=_VLUbhNz6Dk"]https://www.youtube.com/watch?v=_VLUbhNz6Dk

Done in CFX:

https://www.youtube.com/watch?v=uZeqHBJuM1o"]https://www.youtube.com/watch?v=uZeqHBJuM1o

And this is done in Fluent using 2 way FSI:

https://www.youtube.com/watch?v=nCmKA0-Tgl8"]https://www.youtube.com/watch?v=nCmKA0-Tgl8

Also consider using the overset mesh...
https://www.youtube.com/watch?v=_Cryhe7L3uw"]https://www.youtube.com/watch?v=_Cryhe7L3uw

Sopho · February 22, 2018, 09:23

Dear Far
Thanks for your response and for the links you provided me. But I still have some questions

1) during a literature survey I did about the turbulence model, I decided to use the kw SST with curvature correction enabled. Could someone tell me if this a good choice?

2) the case I want to model is the following
Moving water at 2 m/s
Stationary air
The cylinder is placed inside the water phase.
In order to simulate this model I have chosen vof with open channel flow. With open channel flow I can use 2 types of boundaries(pressure inlet and mass flow inlet)
When I use mass flow inlet, messages of reversed flow and limited viscosity appear.When I use pressure inlet I can't make the air to be stationary. If someone could enlight me on this problem I would aprecciated it a lot

3) I also want to calculate vortex shedding angular frequency. I think that the right way to do that is from the cl chart. Do you think this is a good approach?

February 20, 2018, 15:11	VIV simulation using FLUENT	#1
Sopho New Member Sophocles Join Date: May 2017 Posts: 2 Rep Power: 0	Hello guys, I am a 4th year engineering student and i'm trying to simulate Vortex Induced Vibration around a cylinder using Fluent, for my diploma thesis. I have read many papers so as to get a good understanding on phenomena and the physics that get involved in, and now i have turned to modelling this phenomenon in Fluent. Before i begin with the simulations of a moving cylinder, i did some simulations of a stationary cylinder. The domain in these simulations was full of water (only water). The results were good and reasonable according to bibliography. Now i want to move on to the next step, and my final goal is to simulate viv around cylinder inside a tank with water and air. Thus, i want to perform a simulation using VOF and Open Channel Flow. But i have some questions.. 1) Which turbulence model is the best for this phenomenon. 2) How can i model hydrostatic pressure? In the region of air the pressure is atmospheric, since it is an free surface, but as you go deeper in the tank the pressure is increasing and is equal to Patm+ρgh. Maybe i could do this, by using a UDF but i don't know how to write this particular UDF. Is there any other possible way to model hydrostatic pressure. I would appreciate if someone shared a similar udf.

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February 21, 2018, 00:40		#2
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Yes this can be done on Fluent. And it is pretty common simulation people are doing. You can find the UDF for 6 DOF on net or even in Fluent UDF manual.

February 21, 2018, 00:44		#3
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	You can also go through many videos on youtube This was done in fluent https://www.youtube.com/watch?v=_VLUbhNz6Dk"]https://www.youtube.com/watch?v=_VLUbhNz6Dk"]https://www.youtube.com/watch?v=_VLUbhNz6Dk Done in CFX: https://www.youtube.com/watch?v=uZeqHBJuM1o"]https://www.youtube.com/watch?v=uZeqHBJuM1o And this is done in Fluent using 2 way FSI: https://www.youtube.com/watch?v=nCmKA0-Tgl8"]https://www.youtube.com/watch?v=nCmKA0-Tgl8 Also consider using the overset mesh... https://www.youtube.com/watch?v=_Cryhe7L3uw"]https://www.youtube.com/watch?v=_Cryhe7L3uw

February 22, 2018, 09:23		#4
Sopho New Member Sophocles Join Date: May 2017 Posts: 2 Rep Power: 0	Dear Far Thanks for your response and for the links you provided me. But I still have some questions 1) during a literature survey I did about the turbulence model, I decided to use the kw SST with curvature correction enabled. Could someone tell me if this a good choice? 2) the case I want to model is the following Moving water at 2 m/s Stationary air The cylinder is placed inside the water phase. In order to simulate this model I have chosen vof with open channel flow. With open channel flow I can use 2 types of boundaries(pressure inlet and mass flow inlet) When I use mass flow inlet, messages of reversed flow and limited viscosity appear.When I use pressure inlet I can't make the air to be stationary. If someone could enlight me on this problem I would aprecciated it a lot 3) I also want to calculate vortex shedding angular frequency. I think that the right way to do that is from the cl chart. Do you think this is a good approach?