Simple Fluid Flow Pipe Problem Crahes

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1

Hallo,

I try to solve a rather simple problim auf water flow in a pipe with one inlet and five outlets.

Inlet ist of constant speed tipe.
Outlets of constant pressure.

The walls are no slip.

I want to know the pressure at teh inlet necessary to creat the flow and the volume flow at the outlet.

To get the outlet flow I record the outlet average speet. That times the are of each outlet gives the volume flow.

For some reason I do not understand the simulation crashes.

I would really appreciat it if someone could take a look and tell me what the problem ist.

Die dimension of the inlet is 10mm diamter. The outlets ae 1mm in diamter and the pips have 6mm diameter.

In teh end I whant to incrementally increase the outlets diameters so that the volumeflow in each outlet is the same and that te necessary driving pressure becomes minimal. So I am looking for the biggest outlet diamters which give an “identical” volumeflow at ervery outlet.

Thanks a lot

Agnes.

2

Hi Agnes,

I had a look at your design. I recommend you try to improve the mesh resolution across the outlets and maybe relax it in the bigger diameter pipes. I see you added an inflation layer at the inlet but not on the rest of the walls? Not sure it will do much for you unless you stay uniform. However, I suggest you remove layers for now (go from simple model to complex). Your geometry is complicated so I suggest you also step it down to laminar first. Your boundary conditions seem right but CFD with many outlets and a path like yours is complicated. Mesh is crucial in this scenario and what I see for your outlets will not be enough (perhaps try parametric to have tight resolution at inlets (with region refinements) and more relax in the bigger pipes… Also double check your calculations. Good luck!

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