Linear motion of a solid inside a fluid

MarinaSS88 · November 10, 2014, 11:46

Dear all,

I'm trying to simulate a solid body moving inside a fluid. I have found several tutorials of rotating solids as incompressible/pimpleDyMFoam/propeller.

Nevertheless the case that I want to simulate consist in a traslational solid, I mean, a body that moves linearly at constant high velocity. As the external geometry of the control volume is variable, I need a dynamic mesh (I would like to move the obstacle, changing the mesh topology).

I use OpenFoam 2.3 version.

Does anybody have any idea of how can I simulate this?
Is there any tutorial that solves a problem similar to the one described?

Many thanks in advance!

Marina

jiahui_93 · February 22, 2018, 01:32

Hi, although it is an old post, would you or anyone mind to share some information? I am doing the same thing as you. I referred to the movingCone case.
Since snappy hex mesh seems not very good in meshing geo with sharp edge. I used blockMesh. i had successfully move my mesh using the mesh which the solid (within the meshed domain) contains internal mesh. The simulation result shows something not logic, so i try to delete the internal mesh in the solid, since my aim is to investigate the external flow around the moving solid. But after deleted soild's internal mesh, when the solid is moving up, it left hole there (on solid original location at t=0).

Attached is the picture showing mesh with solid body internal mesh (smooth plane) and mesh without solid body internal mesh (plane with a hole which is solid body)
Picture1.png

Capture.PNG

May i know is it wrong that i delete the mesh inside the solid? (I dont want to investigate the internal flow in solid, i only want to investigate the external flow between the solid external wall and the domain.

Is openfoam confuse on the internal field for soild body and domain, so give a not logic result?

Snappy hexMesh gave me the mesh with only external mesh, which is what i want, but with high non orthogonality and skewness. blockMesh provide good cell but the problems as i mentioned above.
My objective is to simulate the external flow of the moving solid body within the fluid domain. Any suggestion or alternative to do so using blockMesh? in order to get something like this in 3D
simplecar.PNG

I would b very grateful and thanks for any comment and suggestions. Thanks

JiaHui

jiahui_93 · March 1, 2018, 05:26

Code:

But after deleted soild's internal mesh, when the solid is moving up, it left hole there (on solid original location at t=0).

Hi, i found out i had done a silly mistake. It solved. Sorry for inconvenient everyone.

Just to share in case anyone doing the same mistake (although no one may do something funny like me

)

I shouldn't spilt mesh after deleted the carCellZone. I should directly run the pimpleDyMFoam. The car hollow box will move up and mesh will be auto replaced

But still facing the problem with low U and P contour being generated by my moving car. I hope to get some suggestions here. Thanks =)

wouter · March 2, 2018, 18:34

Hello jiahui_93,
Why not leave the car still and the air move around it, like i a windtunnel?
there are tutorials doing this with a motorbike.

hope this helps,
Wouter

wouter · March 2, 2018, 18:35

Hello jiahui_93,
Why not leave the car still and the air move around it, like in a windtunnel?
there are tutorials doing this with a motorbike.

hope this helps,
Wouter

jiahui_93 · March 2, 2018, 20:46

Quote:

Originally Posted by wouter

Hello jiahui_93,
Why not leave the car still and the air move around it, like i a windtunnel?
there are tutorials doing this with a motorbike.

hope this helps,
Wouter

Hi, Thanks for the suggestion. Yes, i have tried that and the result looks logic. I thought i am trying to create something closer to the reality which is solid obstacle moving within a domain instead of assuming by using static obstacle and moving air and domain. I saw the moving cone and water stiring case had successfully done with U,P and turbulent production by the movement of solid obstacle. I hope can achieve the same result.

I even tried fvOptions. But it doesn't help in my case and i am still struggling with some unreal result and errors

Do you have any suggestion on this?

Btw, thanks again for your suggestion

have a nice day

Bodo1993 · May 4, 2021, 17:39

Hi,
I want to do the same concept, move two solid walls from the fluid domain geometry. I do not have a dynamic mesh library in my solver and I would like to try fixing the solid walls and move the fluid. Can anyone provide me with a suggestion on how to start or share a simple toy case?
Thank you in advance.

November 10, 2014, 11:46	Linear motion of a solid inside a fluid	#1
MarinaSS88 New Member Marina Sierra-Sesumaga Join Date: Nov 2014 Posts: 2 Rep Power: 0	Dear all, I'm trying to simulate a solid body moving inside a fluid. I have found several tutorials of rotating solids as incompressible/pimpleDyMFoam/propeller. Nevertheless the case that I want to simulate consist in a traslational solid, I mean, a body that moves linearly at constant high velocity. As the external geometry of the control volume is variable, I need a dynamic mesh (I would like to move the obstacle, changing the mesh topology). I use OpenFoam 2.3 version. Does anybody have any idea of how can I simulate this? Is there any tutorial that solves a problem similar to the one described? Many thanks in advance! Marina

February 22, 2018, 01:32		#2
jiahui_93 Member Join Date: Jan 2018 Location: Malaysia Posts: 58 Rep Power: 8	Hi, although it is an old post, would you or anyone mind to share some information? I am doing the same thing as you. I referred to the movingCone case. Since snappy hex mesh seems not very good in meshing geo with sharp edge. I used blockMesh. i had successfully move my mesh using the mesh which the solid (within the meshed domain) contains internal mesh. The simulation result shows something not logic, so i try to delete the internal mesh in the solid, since my aim is to investigate the external flow around the moving solid. But after deleted soild's internal mesh, when the solid is moving up, it left hole there (on solid original location at t=0). Attached is the picture showing mesh with solid body internal mesh (smooth plane) and mesh without solid body internal mesh (plane with a hole which is solid body) Picture1.png Capture.PNG May i know is it wrong that i delete the mesh inside the solid? (I dont want to investigate the internal flow in solid, i only want to investigate the external flow between the solid external wall and the domain. Is openfoam confuse on the internal field for soild body and domain, so give a not logic result? Snappy hexMesh gave me the mesh with only external mesh, which is what i want, but with high non orthogonality and skewness. blockMesh provide good cell but the problems as i mentioned above. My objective is to simulate the external flow of the moving solid body within the fluid domain. Any suggestion or alternative to do so using blockMesh? in order to get something like this in 3D simplecar.PNG I would b very grateful and thanks for any comment and suggestions. Thanks JiaHui Last edited by jiahui_93; February 23, 2018 at 12:27.

March 1, 2018, 05:26		#3
jiahui_93 Member Join Date: Jan 2018 Location: Malaysia Posts: 58 Rep Power: 8	Code: But after deleted soild's internal mesh, when the solid is moving up, it left hole there (on solid original location at t=0). Hi, i found out i had done a silly mistake. It solved. Sorry for inconvenient everyone. Just to share in case anyone doing the same mistake (although no one may do something funny like me ) I shouldn't spilt mesh after deleted the carCellZone. I should directly run the pimpleDyMFoam. The car hollow box will move up and mesh will be auto replaced But still facing the problem with low U and P contour being generated by my moving car. I hope to get some suggestions here. Thanks =)

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March 2, 2018, 18:34		#4
wouter Senior Member Wouter van der Meer Join Date: May 2009 Location: Elahuizen, Netherlands Posts: 203 Rep Power: 18	Hello jiahui_93, Why not leave the car still and the air move around it, like i a windtunnel? there are tutorials doing this with a motorbike. hope this helps, Wouter

March 2, 2018, 18:35		#5
wouter Senior Member Wouter van der Meer Join Date: May 2009 Location: Elahuizen, Netherlands Posts: 203 Rep Power: 18	Hello jiahui_93, Why not leave the car still and the air move around it, like in a windtunnel? there are tutorials doing this with a motorbike. hope this helps, Wouter

May 4, 2021, 17:39		#7
Bodo1993 Senior Member Join Date: Jul 2019 Posts: 148 Rep Power: 7	Hi, I want to do the same concept, move two solid walls from the fluid domain geometry. I do not have a dynamic mesh library in my solver and I would like to try fixing the solid walls and move the fluid. Can anyone provide me with a suggestion on how to start or share a simple toy case? Thank you in advance.