Tuesday, April 9, 2024

How to solve below problem in Ansys Fluent Divergence detected in AMG solver: temperature?

 The error message "Divergence detected in AMG solver: temperature" in Ansys Fluent indicates that the solver is having difficulty converging on a solution for the temperature field. Here are some steps you can take to address this issue:


**Understanding the Errors:**

* **Limited Absolute Pressure:**  The message "absolute pressure limited to 5.000000e+10 in 32400 cells on zone 2" suggests that the pressure values in some cells (zone 2) are reaching a very high limit. This could be due to an incorrect pressure boundary condition or a physical inconsistency in your model.

* **Limited Turbulent Viscosity:**  The message "turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 2150 cells" indicates that the turbulent viscosity is being limited in some cells. This could be happening due to very high or low velocity gradients in those cells.


**Troubleshooting Steps:**

1. **Check Boundary Conditions:**  Double-check your pressure boundary conditions for zone 2. Ensure they are set correctly and don't lead to unrealistic pressure values.

2. **Refine Mesh:**  A coarse mesh can sometimes lead to convergence issues. Try refining the mesh, particularly in areas with high pressure gradients or complex geometry.

3. **Relaxation Factors:**  Adjusting relaxation factors for temperature, pressure, and other relevant variables can sometimes help the solver converge. Start with smaller values and gradually increase them.

4. **Under-Relaxation:**  Enable under-relaxation for temperature and pressure. This helps the solver take smaller steps towards the solution during each iteration, potentially avoiding divergence.

5. **Solver Initialization:**  Try initializing the solution from a simpler case or a previous converged solution (if available).

6. **Solver Settings:**  Experiment with different solver settings like convergence criteria and residuals targets.

7. **Model Geometry:**  Review your model geometry for any inconsistencies or sharp corners that might be causing numerical problems.

8. **Material Properties:**  Ensure your material properties for temperature and other relevant fields are entered correctly and within reasonable ranges.


**Additional Tips:**

* Consult the Ansys Fluent documentation for detailed information on convergence issues and troubleshooting tips: [https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/main_pre.htm](https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/main_pre.htm)

* Search online forums and communities for similar problems and solutions related to your specific case. 

* Consider contacting Ansys support for further assistance: [https://www.ansys.com/support](https://www.ansys.com/support) 

By systematically troubleshooting these potential causes and adjusting your model setup, you should be able to resolve the divergence issue and achieve a converged temperature solution in Ansys Fluent.


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