FLUENT System Coupling Error

Hi everyone,

I created a system coupling between a FLUENT and a steady-state thermal modules. Two of them are 2-way coupled using temperature, film coefficient and reference temperature. Initially, I turned off energy equation in FLUENT and let the system coupling run for 5 coupling iterations, just to see how it behaved. It worked nicely, only the FLUENT model didnt converge but I did not expect it to. Then I turned on the energy equation and repeated the system coupling, when following errors occured:

I suppose that the hihlighter message is the main cause of issue: "A large negative pivot value ( -1.768436371E-03 ) has been encountered in the global assembled matrix at the TEMP degree of freedom of node 5795. This may be caused by a bad temperature-dependent material property used in the model". I am using liquid water from FLUENT's database, which has constant material properties. Would switching these to temperature dependant ones possibly solve the problem?

Anyone has an another idea what could be the issue? I am using ANSYS 17 if it is relevant.

Thanks in advance,



  • RobRob UKForum Coordinator

    Check what Mechanical is seeing re the temperature. It looks more like an issue with the solver than system coupling. How does it look in 2020R2 as R17 is about 4 years old.

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