# Moving Reference Frame interFoam

 Register Blogs Members List Search Today's Posts Mark Forums Read

 November 5, 2016, 18:04 Moving Reference Frame interFoam #1 Member   Arsalan Join Date: Jul 2014 Posts: 74 Rep Power: 12 Dear Foamers, I'm doing some simulations of bubble rising in the quiescent liquid under gravity using interFoam. In order to reducing computational costs, I want to use a moving reference frame that follows the bubble during rising in the liquid in a manner that bubble placed in the middle of geometry. I have no idea about this purpose except Rusche's Phd thesis, but there is nothing about implementation of that! Any help and comment will be appreciated. Regards, Arsalan.

 November 8, 2016, 09:27 #2 Member   Arsalan Join Date: Jul 2014 Posts: 74 Rep Power: 12 Dear Foamers, According to Rusche's phd thesis, I should add the bubble acceleration in each time step to the momentum equation and also set velocity *BC's to the bubble center of mass velocity in a reverse direction. Already I did these, but after 0.0025 s the solvers blows up because a very low time step value. An another option is adding the bubble acceleration to the momentum equation again, and use dynamicMesh option for mesh movement. For this purpose, I modified a solid body motion function ("linearMotion") to a new function called "bubbleMotion" and set the vector displacement to bubble displacement as follows: Code: ``` // Translation of centre of gravity const vector displacement = xF; //xF=bubble displacement vector``` The library and solver successfully compiled in this manner, but bubble displacement vector isn't updated for mesh movement, while xF is calculated and updated for each time step in the solver. How should I tell the function to update xF for each time step? I'm waiting for your comments about either of two methods. Thanks in advance. Regards, Arsalan.

 Tags bubble rising, interfoam, moving mesh, moving reference frame