# Boundary conditions for two connected fluid region.

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 October 21, 2010, 16:29 Boundary conditions for two connected fluid region. #1 New Member   Anh Le Join Date: Jul 2010 Posts: 5 Rep Power: 13 Hi, I want to creat two different fluid regions with different meshes. The outlet of region 1 will connect to the inlet of region 2. Assuming the flow goes through the inlet of region 1 to outlet of region 2. Then, the BCs for U and P should be: -Region 1, inlet: U fixed value, P zeroGradient - Region 2, outlet: U zeroGradient, P fixed value (0 - ambient pressure) So, what should BCs for U and P at: Outlet of Region 1 and Inlet of Region 2 (actually, they coincide but in different meshes). The BC patches of Outlet, region 1 and Inlet, region2 should be "regionCouple" ??? Many thanks for helping me out of this.

 December 4, 2012, 06:23 defining internal boundary conditions #2 Member   Jamal Join Date: May 2012 Location: Freiburg Posts: 54 Rep Power: 11 Dear solver:chtMultiRegionFoam version: OF-2.1.0 geometry: containing a number of fluid regions surrounded by solid regions. Its like a 2D rectangle with solid walls having inlet/outlet fluid regions and internal fluid regions. problem: coupling solid/fluid regions in the same way as defined in tutorial but how to couple fluid/fluid regions (right now i am using zeroGradient for U,T, p) and solid/solid regions. And as I use to run the simulation, after some iterations temperature goes to very high values. Thanks Jamal

 December 5, 2012, 00:07 #3 Member   Join Date: Nov 2010 Location: Tokyo / Japan Posts: 40 Rep Power: 13 Hey Jamal and Anh, have a look at http://www.cfd-online.com/Forums/ope...tml#post395838 Linse, ZKW and me are working on the same issue.

 June 20, 2019, 16:45 Two touching fluids for heat transfer in OpenFOAM #4 Member   Join Date: Mar 2019 Posts: 81 Rep Power: 5 Hi there, Sorry for reactivating this dormant thread. I have a very basic question! I know that in many CFD software two fluids should be separated by a solid unless they form a mixture (i.e. VOF). This is not the case in my simulation. I want to simulate heat transfer using chtMultiRegionSimpleFoam between two fluids. The geometry is similar to a double pipe heat exchanger. Since OpenFOAM is inherently different from many other solvers, I was thinking whether it is possible to couple the two fluids directly (without simulating the sandwiched solid between them). If yes, what should be assigned in the shared boundaries? I tried some cases but am getting divergence after few iterations (negative temperature) Thanks a million in advance... kraf likes this.