Hi friends, I am doing pipe flow simulation (supercritical CO2) in Fluent. I am trying for different heat input. all boundary conditions are same for all cases. three heat input values solution is perfectly converged (before 3000 iteration).But when move to high heat values, residual lines are moving in straight line not converging(even after 12200 iteration) I tried with low relaxation factor (Density value changed to 0.6 from 1) but not worked.
Any solution for this?
When performing simulations in computational fluid dynamics (CFD) software like Fluent, convergence issues can arise due to various reasons, especially when you change the operating conditions, such as the heat input. The fact that your solution is converging for lower heat input values but not for higher heat input values suggests that the problem might be related to the increased complexity or nonlinearity introduced by higher heat inputs. Here are some common reasons why convergence might be difficult to achieve in such cases:
If you have already tried lowering the relaxation factors and it did not help, you can try refining the mesh and reducing the time step as the next steps. Additionally, monitoring the residuals and solution fields can give insights into which parts of the domain are causing difficulties in convergence.
It's also important to note that some simulations, especially those involving complex physical phenomena, may require significantly more iterations to converge fully. If the solution is stable and slowly improving, it might be acceptable to continue the simulation until convergence is achieved.
Kristaq Hazizi
Sir, Your suggestions are very much valuable to me, thanks a lot for replying to me. i will try these tips and hope I ll solve the problem very soon.
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