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residual scaling and convergence

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Old   November 8, 2009, 08:35
Default residual scaling and convergence
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Hi,

I'm simulating axial compressor blade flow.

When I'm doing a single passage (one blade), the residuals go down to 1e-04 to 1e-05 for continuity and the velocities and 1e-07 for nut (spalart allmaras turbulence model).

When I'm doing calculations with e.g. 7 passages, the residuals go just down to 1e-02, although nut converges to 1e-07.

So the passages are all the same and so are the boundary conditions. Actually this calculation should give the same results as the single passage calculation, but the residuals don't look as good as supposed to.

I'm wondering whether this is just because of the scaling of the residuals.

Has anybody made similar experiences or does anybody know about how to judge such residuals?

I'm grateful for all posts.
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