Continuity residual remain around 10E-01 in 2D steady Fluent Simulation

[Yingkun Wang]

Hello,

I am running a 2D steady-state internal flow simulation in ANSYS Fluent 2026 R1 for a turbine-blade internal cooling study. The model contains a main air region and four porous regions. I am using the SST k−ω turbulence model with the energy equation enabled.

My main problem is that the continuity residual decreases initially but then remains nearly flat at approximately 10E-01, while the other residuals continue to decrease.

I also monitor pressure during the calculation. The pressure-related monitor continues to increase with iteration instead of reaching a stable plateau, so I do not consider the solution converged yet.

I would like to understand:

1. What are the most likely reasons for the continuity residual remaining around 10E-01 when the velocity, turbulence, and energy residuals have decreased significantly?
2. Is reducing the momentum under-relaxation factor an appropriate approach, or should I focus instead on boundary conditions, mass imbalance, pressure-velocity coupling, or mesh resolution?
3. What additional quantities should I check to determine whether the problem is numerical or whether the flow may be inherently unsteady?

I have attached screenshots of the residual history, mesh, and mesh-quality statistics. I can also provide the boundary-condition and solver-setting screenshots if needed.

Thank you for any suggestions.

[Rob]

We'd need to see what the flow is doing. Stuck residuals can be any of the options you mention, but could also be showing some transients in the solution.