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Hi,

I have set up a 3D laminar flow problem in a rectangular geometry with an inlet and outlet. The problem presents in reality a fluid exchange problem: a box of dilute chemical solution is connected to a pump, where an inlet introduces solution with a different chemical concentration and temperature while the fluid in the box is expelled through the outlet. The top surface of the box is open to ambient envrionment.

The physics involved are: laminar flow, heat transfer, transport of dilute species, and the couplings between them (nonisothermal flow and flow coupling)

When I simulated laminar flow and heat transfer separately, they converge to resonable solutions. Once I turn on laminar flow and heat transfer together, the simulation diverge with error message "Nonlinear solver did not converge. Maximum number of segregated iterations reached. Time : 1.000210409321674 Last time step is not converged."

I used a segregated solver and the convergence plot shows that laminar flow has a hard time to converge. I checked my boundary and initial conditions but they seem fine.

Can someone suggest any reason that possibly causes the convergence problem, and what would be the solutions?

Thanks. Thanks.