# Convergence Criteria for Two Fluid Flow Solver

Which one of the following is suitable for judging convergence in Two-Fluid Flow Solver?

1) Absolute Residual (L^2-Norm).

2) Relative Residual.

3) Fraction Change in Velocity, Pressure and Volume Fraction.

I am asking this question because due to large value of momentum exchange coefficients one can get very high value of absolute residual even when solutions are close to actual value.

Is there any other criterion used?

• It seems there may be two parts to your question: 1) whether the numerical convergence of an iterative method has reached an acceptable accuracy, or 2) whether the fluid flow has reached a steady state (as your part 3 suggests). The third answer by @NamRakes addresses your last part, and the other two answers seem to be options for your first two parts. – Charles Apr 25 '16 at 7:02

3. Verify that $\Delta$Energy due to "incremental DOF times residual" is small compared to, say, the energy input to the system.