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Problem solving a flow with inlet pressure

Posted 2017年11月22日 GMT-5 09:16 2 Replies

Pascalin Tiam Kapen
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Hi,

I have to model a flow of Helium inside a micronozzle (inlet diameter = 5 mm and outlet diameter = 1mm) and all I am given is the inlet pressure (30 bars), and the pressure at the other side of the micronozzle is ambiant pressure. The tube is 23 mm. The issue I'm facing is that the solver can't find a solution if I just put an inlet and outlet with pressure, no viscous stress as BC. I tryied both laminar and turbulent flow.

I know it has been discussed a few times in the forum but I wasn't able to find a thread resolving my problem. I don't know if I missed something in comsol or simply with the actual phenomena.

If someone knows what I could do step by step, Thanks in advance!

2 Replies Last Post 2017年11月22日 GMT-5 09:59
Vasily Kozhevnikov
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Posted: 7 years ago 2017年11月22日 GMT-5 09:43

Hi,

When you define inlet pressure and outlet pressure you turn to "hindered" convergence. Well-posed CFD problems always combine velocity-pressure conditions, e.g. velocity at inlet and pressure at outlet or vice versa. When you'd like to define pressure at inlet and outlet - you have to seriously refine grid at inlet where the pressure is greater.

Hi, When you define inlet pressure and outlet pressure you turn to "hindered" convergence. Well-posed CFD problems always combine velocity-pressure conditions, e.g. velocity at inlet and pressure at outlet or vice versa. When you'd like to define pressure at inlet and outlet - you have to seriously refine grid at inlet where the pressure is greater.
Pascalin Tiam Kapen
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Posted: 7 years ago 2017年11月22日 GMT-5 09:59

Thanks Vasily, I still have the same problem. I tried to refine the mesh at the inlet of the micronozzle but the same error persists. How should i do step by step?

Thanks Vasily, I still have the same problem. I tried to refine the mesh at the inlet of the micronozzle but the same error persists. How should i do step by step?

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