[Tens]

I used chtMulitRegionSimpleFoam in OpenFOAM-v2112, and found that whether the useImplicit is true or not has a significant impact on the results.
When the useImplicit was false, I got a higher temperature which is close to the result of Fluent.But when the useImplicit was true, I got a lower temperature.
The point is using Implicit spending less time than not using it, usually a dozen times faster.
1.Why does useImplicit have such a big impact on the results?
2.How to get more accurate results in less time?

[zhoulei_3c]

Hello, Do you have solved the problem or find why this happening?

[dasa]

"useImplicit - true" will help the solver to converge the temperature quickly when you have cyclic, cyclicAMI, cyclicACMI, and mapped boundary conditions.

When you set "useImplicit - true" and parallel run, you must have your coupled patches on the same processor.

It will not affect your results, and you should get the same result with "useImplicit - true" & "useImplicit - false."