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Diveregence detected in AMG solver: x-momentum

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Old   August 14, 2010, 05:09
Default Diveregence detected in AMG solver: x-momentum
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Arash
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Hello everyone,

I've designed a blade for a turbine and now I'm trying to analyze it in 3D by FLUENT. As the blade is rotating I need to use moving reference frame for the fluid and set the blade as moving wall with the angular speed of 0 rad/s right ? when I try to run the case I get this error: 'Divergence detected in AMG solver: x-momentum' . I've checked my boundary conditions they seem ok and I reduced the relaxation factor for momentum but still I get the same error. could you please help me with and tell me what this error means, I don't know if the problem is because I'm not defining the boundary conditions correctly or there's something wrong with my mesh or for something else.

thank you,
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Old   August 15, 2010, 00:14
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The blade should be set to a rotational speed of zero relative to adjacent cell zone. And it is recommended that you initialize your solution with zero for all components of velocity under relative reference frame.
Other stratigies for the problem are:
use PRESTO!scheme for pressure discretization;
start the solution with a low speed, and then gradually increase the speed.
By the way, do you have a stator in the configuration?
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Old   August 18, 2010, 07:28
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Thank you very much,

I solved my case and now the results seem ok beside the blade torque which is not even close to the one I calculated by hand. no there is no rotor the blade is for a tidal turbine, tidal turbines are very similar to wind turbines.
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Old   August 18, 2010, 07:47
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Numerical simulation is not easy.
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