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correction is just a rough approximation to conservation equations.
when you apply the SIMPLE algorithm to solve a problem, under relaxation factor will be used to calculate the velocity and it does not make a sence to be applied again in velocity correction step. for example, consider that you have a very complex geometry and you are obliged to use a very small under relaxation factor, say 0.1,. if you apply this factor to momentum equation it will reduce convergence rate considerably but it has no influence on the converged velocity field. but now imagine that you apply 0.1 in the correction step. what will happen? u' or P' will recieve a huge unrealistic change and it may leads in divergence. |

Thank you for the reply, I'm not sure, however, I understand 100%...
You say that introducing under-relaxation may lead to too high velocity change/correction. As I see it, if I have velocity under-relaxation then should decrease with increasing under-relaxation... And, if I then apply the pressure under relaxation factor I get , which then decreases the velocity correction even further. In the end, of course, it should not matter for a converged solution. However, to get there is the key issue :-) Regards |

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