I'm trying to simulate using Finite Elements (non commercial software) the Tube Bundle benchmark problem: http://cfd.mace.manchester.ac.uk/ercoftac/doku.php?id=cases:case078&s=tube&s=bundle
Many authors (e.g. Benchmark Simulation of Turbulent Flow through a Staggered Tube Bundle to Support CFD as a Reactor Design Tool. Part II: URANS CFD Simulation) have used a single periodic cell (the right picture in Fig. 1) as their computational domain, with periodic boundary conditions. To maintain the flow rate, they impose a constant, prescribed flow rate via pressure gradient/body source term.
Here is where I would appreciate some help. I have a math background, and I was not able to find any literature that explains how exactly this is done. The trial-and-error approach didn't help.