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Old   April 19, 2018, 13:56
Talking Convergence
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I am simulating flow in an axial flow compressor near choking point.
There is a bellmouth at the inlet of compressor as shown.
I have two questions:
1. Can the bellmouth be added to the rotor domain in the bladegen? I saw it in a tutorial (axial fan) that the intake was included in the domain of rotor. I am using solidwork to draw a section of intake and then use a general interface to connect the bellmouth and the rotor.
2. When I simulate near the choking point, the residual history shows that the momentum components go up and down and the solution never converges. Does this occur because of wrong BC? I am using static pressure bc at the outlet.
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Old   April 19, 2018, 19:03
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1. Yes, it can rotate. Make the walls counter rotating if they are stationary.
2. FAQ: https://www.cfd-online.com/Wiki/Ansy...gence_criteria
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Old   April 20, 2018, 16:04
Post Intake effects
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Does a big axial gap between the bellmouth and the first blade row which might happen in a static test rig justify ignoring its influence on downstream components? Besides performance map, what can be used to measure its influence and justify ignoring its effects?
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Old   April 22, 2018, 08:32
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Quote:
Does a big axial gap between the bellmouth and the first blade row which might happen in a static test rig justify ignoring its influence on downstream components?
I have no idea. That depends on many, many factors.

Quote:
what can be used to measure its influence
Good question! I would recommend simply doing a simulation with the bell mouth included and one with it removed an compare the simulation results for parameters of importance to you. This is called a sensitivity study and you should always check things you are not sure of, so I am glad you asked this question.
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