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  • Lesson 17 – Residual doubt

    Posted by MARCO on March 17, 2024 at 11:43 am

    Hi all,

    I have a doubt regarding the lesson 17. In particular it is not so clear to me the difference between the initial residual (for each flow field parameter) and the final Residual. I looked up some online resources finding out that final one should refer to the residual obtained from the iterations corresponding to the linear equations system solver (SOR, Jacobi, Gauss Siedel for instance). However it is not so clear to me the concept of the initial residual, because it is often defined as a residual obtained updating the the A matrix corresponding to the linear system and I’m struggling in understanding how this update is made. I’m so sorry for my ignorance and my english.

    Thanks in advance.

    Kind regards,


    MARCO replied 3 weeks, 1 day ago 1 Member · 1 Reply
  • 1 Reply

    March 29, 2024 at 6:31 am

    Hi, I almost figured out what was the mistake I made. Obviously, for each solver, an algoritm for the calculation of the terms of the equations, and the parameters of the flow field, Is implemented. This means that, After having calculated the final residual for the current time step, the results should be coupled and corrected due for instance to conservative conditions, pressure gradient-velocity relation and so on.

    Eventually, due to the above corrections, the residual will become generally higher than the final one and Will be taken as convergence parameter at the beginning of the next time step.

    I surely made errors in myb explanation. Aplogies for the length.

    Kind regards,


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