Wall between porous zones
 

Hi CFD users! I have one problem. I simulate (in Fluent 14.5 version) the flow of water through the row of paralel tubes. Tubes are simulated as porous zones with different power (source terms) and every tube is divided to 4 parts (down to up). I defined walls between tubes - with no heat flux, so the boundary condition is isotermic. Walls are not divided to 4 parts as tubes. My problem is following: there should be isotermic condition along the whole wall and there is the wall, but in temperature or velocity contours, it seems as expansion of flow ("bubble" of different temperature and velocity) but only in small areas in points where two porous parts of tube touch to each other. I dont know, if there is some mistake in setting of porous zone placed next to other porous zone, or if i have to divide the wall to 4 parts in a same case as the tube is divided, or where is the mistake? So do you have some similar experiences in defining walls placed between two (or more) porous zones? I added two pictures of velocity and
temperature in down half of model.

Thanks a lot for your recommendations and advices.

appendix
 

I forgot.... the velocity inlet is the whole bottom of the geometry, the model is 3D and tubes mean square channels.

Thanks a lot.