### 15.6.4. Hydro Control

These settings become active from the first iteration through to the specified transition iteration. The default transition iteration is zero; that is, the settings are not used unless you set a transition iteration.

Sum Continuity Coefficients is only applicable to compressible flows. This forces/enhances diagonal dominance in the solution matrices for more robust startup. It has no effect on the steady solution, but should be turned off using the transition iteration after a few iterations as it would begin to retard convergence.

Free Surface Harmonic Averaging has the same effect as the Harmonic Body Force Averaging option (see below), but enables you to use harmonic averaging (more robust) during startup and then revert back to the default body force treatment after the transition iteration is reached.

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