Hello,
I am new in Ansys and trying to carry out the 2D CFD analysis of duct with circular transverse roughness rib. First, I used uniform mesh (number of nodes was nearly 1,57000 and element size 0.24mm) and I got smooth convergence. But , when I used size function 'Curvature' (element size is same 0.24mm and number of nodes increased to 159000) and then my residual values started to vibrate excessively after 70 iteration.
Can anyone tell me why this is happening and how it could be smoothly converge.
Thanks
This can mainly be attributed to the fact that your mesh is not good. In the first case you had a structured grid and that will solve no matter the element size smoothly.
In the second case you used curvature and hence your mesh would look like a distorted lot. (triangular mesh). (not sure if this happened in your case. But correct me If I'm wrong)
In the unstructured mesh, the mesh skewness needs to be below 0.98 for smooth convergence. Check your mesh skewness and aspect ratio and improve the quality of your mesh, and this would help you in getting a better convergence.
Another factor that might add to the instability might the solver model. Try a different model and check.
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