getting confused with FSI subiteration

zhaozhenkai · January 27, 2016, 12:52

Hi guys,

I am trying to do a multi-body case in Openfoam. I have used an external programme to send position data of each body to OpenFoam and send the calculated Fluid forces back to the external programme. However the simulation blows up quickly. I have checked the code many times and finally suspect the problems existed in the coupling part. In order to find fixed point between fluid/solid, I want to do sub-iteration in each time step in the customised motionSolver .

Could you guys give me some suggestions about where to find some examples for that or if possible, giving me several lines of code to help me get through the problem?

looking forward to your reply

ZHENKAI

chriss85 · January 28, 2016, 06:20

In the end the solution will be specific to the program you're using to do the coupling. You will need some information if you are in a new time step or subiteration step to account for it in both programs. Then you should be able to use the same loop in both programs. You might also have to synchronize a convergence criterion between them to be able to stop the loop after convergence. A fixed loop iteration might also work, but it's likely less efficient and/or stable.

January 27, 2016, 12:52	getting confused with FSI subiteration	#1
zhaozhenkai New Member ZHENKAI ZHAO Join Date: Oct 2015 Posts: 14 Rep Power: 11	Hi guys, I am trying to do a multi-body case in Openfoam. I have used an external programme to send position data of each body to OpenFoam and send the calculated Fluid forces back to the external programme. However the simulation blows up quickly. I have checked the code many times and finally suspect the problems existed in the coupling part. In order to find fixed point between fluid/solid, I want to do sub-iteration in each time step in the customised motionSolver . Could you guys give me some suggestions about where to find some examples for that or if possible, giving me several lines of code to help me get through the problem? looking forward to your reply ZHENKAI

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January 28, 2016, 06:20		#2
chriss85 Senior Member Join Date: Oct 2013 Posts: 397 Rep Power: 19	In the end the solution will be specific to the program you're using to do the coupling. You will need some information if you are in a new time step or subiteration step to account for it in both programs. Then you should be able to use the same loop in both programs. You might also have to synchronize a convergence criterion between them to be able to stop the loop after convergence. A fixed loop iteration might also work, but it's likely less efficient and/or stable.