Helical pipe flow not converging

MisterTummy · May 8, 2018, 14:00

Hi there,

I have two simulations of a pipe with a junction at an angle. Both the simulations have exactly the same parameters, the only thing that varies is the geometry (one of them has both pipes straight, the other has a pipe with a helical shape). I have solved a steady solution and both converged to a reasonable amount. However, once I run an implicit unsteady solver, only the straight pipe sim converges, the other diverges.

I have no idea why they won't both converge.

Parameters are:

- base size 0.02m
- implicit unsteady timestep: 0.01s
- Re = 800

- Laminar solver
- Segregated flow solver
- Constant density

Inlet is a velocity profile at the left and a negative velocity profile on the right, and a pressure outlet on the top.

Thanks for your help

fluid23 · May 8, 2018, 15:23

Show a plot of your residuals for your diverging transient case.

MisterTummy · May 8, 2018, 16:23

Thanks for offering help though

May 8, 2018, 14:00	Helical pipe flow not converging	#1
MisterTummy New Member anon Join Date: Feb 2018 Posts: 5 Rep Power: 8	Hi there, I have two simulations of a pipe with a junction at an angle. Both the simulations have exactly the same parameters, the only thing that varies is the geometry (one of them has both pipes straight, the other has a pipe with a helical shape). I have solved a steady solution and both converged to a reasonable amount. However, once I run an implicit unsteady solver, only the straight pipe sim converges, the other diverges. I have no idea why they won't both converge. Parameters are: - base size 0.02m - implicit unsteady timestep: 0.01s - Re = 800 - Laminar solver - Segregated flow solver - Constant density Inlet is a velocity profile at the left and a negative velocity profile on the right, and a pressure outlet on the top. Thanks for your help

May 8, 2018, 16:23	I've solved it	#3
MisterTummy New Member anon Join Date: Feb 2018 Posts: 5 Rep Power: 8	Thanks for offering help though

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May 8, 2018, 15:23		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	Show a plot of your residuals for your diverging transient case.