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eromon84 August 12, 2013 01:14

Errors with nozzle_rotor periodic repeat interface
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Hi there,

I am trying to model an unsymmetrical supersonic nozzle with a Curtis wheel rotor arrangement. Unfortunately the number of nozzles is 20 and the number of rotors are 151, resulting in a 1: 7.55 ratio.

From the description of periodic repeats though it seems I could still manage to model this somehow, so I set up the mesh as seen below. Please ignore the red regions. I do have a reason for these but it would take very very long to explain and they are indeed required for what I am trying to do.

The yellow mesh is my rotor with the left blue mesh being the rectangular nozzle and the right blue mesh being a stationary blade row in the Curtis wheel arrangement.

When I try and run this in fluent I get flow build ups along the interface where the rotor mesh is not there, almost like as if fluent is treating it like a wall. This is meant to be a periodic repeat interface and at these empty areas I thought fluent was meant to assume there was another rotor there?

Can anyone help me understand if this is what is meant to be happening? and if so what exactly am I doing wrong?

Thank you.

duri August 12, 2013 12:03

When the periodicity is not met between rotor and stator, you need to use phase lag boundary condition. Otherwise you can't simulate correct physics. I am not sure whether fluent has that or not. But you can simulate some sector of wheel where periodicity is taken care. For example, if you have 12 rotor and 16 stator blades then simulate quarter wheel (3 rotor and 4 stator).
With mixing plane model another approach you can get some approximate results.

eromon84 August 17, 2013 13:24

Hi Duri,

Aplogies for delayed response and thank you very much for your response. I does seem to work correctly this way now; thanks again.

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