Ansys Fluent: Oscillating Cylinders With Dynamic Mesh

This video shows how to setup a simulation showing the vertical vibration of cylinders due to a laminar flow in their surroundings. This process makes use of the dynamic mesh tool.
#Ansys #AnsysFluent #CFD # AutoDesk Inventor.

[@fluentsetup1232]

Here is the result (I forgot to put it at the end of the video): ruclips.net/video/2A6rjbq1-ag/видео.html

[@nguyenquangduy4883]

Thank you for sharing such an interesting tutorial. May I ask why the spring constant is set to zero? how the cylinders can oscillate without a restoring force?

[@akshaypraveen1261]

I have a couple of doubts why we create a separate boundary in the setup module around the cylinder and then separate it from the inlet ....and i understood that velocity is given as a time decaying function or so is the problem like that ...like u want it to simulate for that particular velocity field as such ...and since material is not assigned water or so the material is air as such by default ryt so this pheneomena is observed for air striking the cylinders ryt

[@mohsenbiabani8612]

Great Video , Thanks... I have a question .... Is it a 1 DOF simulation or 2DOF ?? If it's 1DOF , Could you also make a 2DOF video ?? That would be great .

[@woraphonwannaviroj8751]

Hello,
Your tutorial is very interesting for me
I am finding out the way to achieve flow past an oscillating cylinder with ANSYS Fluent and now I’m struggled
I watched your video and i saw that udf function havent used.
This is the new function for latest version 2021?

[@fluentsetup1232]

It isn't a new function, this project could be done exactly the same on previous versions of Ansys. In this case an UDF is not necessary, (although you could use one if you wanted) cause I'm only defining the mass of the cylinders which can be done with the six DoF option. If I wanted to define the motion of the cylinder then I would need an UDF for sure.

[@woraphonwannaviroj8751]

@@fluentsetup1232 Thanks for your answer
Do you have udf for oscillating cylinder?

[@fluentsetup1232]

@@woraphonwannaviroj8751 Not at the moment; but i can send you a link. My question is if you need an udf to define the motion of the cylinders or an udf to define the mass and inertia moment of the cylinder

[@woraphonwannaviroj8751]

@@fluentsetup1232 I would like to change a stationary of cylinder and group of cylinders (my work has 2parts) to oscillating cylinders with an constant frequency then I’ll define their force coefficient and momentum of flow behind them
I thank you a lot for your help and would you mind if i contact you via e-mail?

[@fluentsetup1232]

@@woraphonwannaviroj8751 Apologies for the late response, I don´t know why Im not getting notifications anymore. But anyways, the closest video i could find for oscillating bodies was this one ruclips.net/video/-DgknC-5U54/видео.html . To get force coefficient is fairly simple, you can define the force being applied on every cylinder and Ansys will shou you those values on the screen and you can also export those values on a .txt file.

[@mahdikh1822]

Thank you for the nice job. Why do you give a finite thickness of 10mm to your domain when you want to simulate a 2D problem?

[@fluentsetup1232]

Can you give me a time stamp? I'm not sure which 10 mm you are refering to.

[@mahdikh1822]

@@fluentsetup1232 Thank you for your reply. I meant the time 1:29 when you extruded the domain in width by an amount of 10mm.

[@fluentsetup1232]

@@mahdikh1822 That amount really doesn't matter. I extrude the sketch by an arbitray length so I can import a 3d body instead of a 2d surface, because Ansys has given me problems in the past when I imported a surface.

[@mahdikh1822]

@@fluentsetup1232 Thank you so much for interesting works and your immediate replies to comments and questions.

[@fluentsetup1232]

@@mahdikh1822 You're welcome, although It usually takes me a lot more to reply.

[@deeper1993]

Excellent video. I have a question. I am simulating a cylinder which is free to move in y direction (transverse to flow). Same as shown in this video but with one cylinder. When I am running the simulation, I keep getting an error "Update-Dynamic-Mesh failed. Negative cell volume detected." and the calculation stops. Any advice on how to tackle this issue?

[@joelreji1075]

Hi
Have you got your problem solved,
Please i also face the same,
Please do share the solution

[@deeper1993]

@@joelreji1075 Try increasing the mesh size and lower the time steps. Negative volume is when the nodes in a grid are getting displaced by large amounts. This might lead to the nodes overlapping each other, like as if the cells have folded with a negative volume.

[@ericantonio5492]

@@deeper1993 I am having the same issues, even lowered to 4000 time steps, with 0.01 precision and increased mesh size...

[@nie3956]

Hi Sir. If I use two cylinders only to make it oscillates at cross flow direction, can I use the same method in this video? I already have the mass of the cylinder..

[@fluentsetup1232]

Of course, it would work just fine. The only change you have to make is, in 11:18, when Six DOF properties are being defined, change the direction from X = 0 and Y = 1 to X = 1 and Y = 0, that would allow the cylinders to oscillate on the horizontal direction

[@AsgharAli-lw7pz]

Your system specifications?

[@nashoghb]

Hola, tienes algún medio de contacto?