[Julian121]

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.

[ghorrocks]

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

[Julian121]

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?

[ghorrocks]

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.

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.