No convergence of simulation
Hello there,
I am having an issue with BaramFlow where none of my simulations are converging. I always get a "Calculation is terminated" pop-up and the residuals have not converged at all. I have attached an example of the residuals while I followed the tutorial for high speed train step-by-step (https://baramcfd.org/en/tutorials-en/tutorial-baramflow-en/tutorial-flow-train-en/). I have tried other tutorials with the same issue occuring in them as well. I have also attached the console logs, should they give any insight.
Any help on this issue will be much appreciated.
Uploaded files:
There seems to have been an issue with the tutorial case.
If you change the turbulent viscosity ratio to 100 in the initial conditions and enable the “Improve Stability” option in the Numerical Schemes, it converges properly.
It appears that the initial value of omega was causing problems with initial stability.
If you download the case by clicking the “Download Simulation” link on the tutorial page and run the solver directly from the terminal without using Baram (using the command `decomposePar' and 'mpirun -np 8 buoyantSimpleNFoam -parallel`), it converges properly. However, if you open this in Baram and run the simulation, it diverges, as you mentioned. This appears to be an issue caused by changes in certain settings following an upgrade to Baram after this tutorial was created.
The high-speed train problem involves a compressible flow at a Mach number of approximately 0.32, and this issue seems to arise within that speed range.
I will investigate further to determine which settings are causing the initial instability.
Thank you for identifying the issue.
We have identified the issue. A bug occurred in v25.1 when determining the initial value for turbulent viscosity. A value smaller than the appropriate one was used, causing issues with initial stability. This issue will be resolved in v26.2, which is scheduled for release in April.