18.5 Looping Structure

To allow flexibility in the control of the solution of the hydrodynamics variables a number of levels of extra loops are available. The solver iteration loops are common to all solved variables so will not be discussed here. The loops of concern in this section are the momentum loop and the hydrodynaimcs loops. The logic of the code at this stage is

• Start of hydrodynamics loop.
• Start of momentum loop.
• Solve momentum components.
• Calculate the velocity differentials.
• Calculate face velocities.
• End of momentum loop.
• Solve pressure correction.
• Update the velocities.
• Calculate the pressure gradients.
• End of hydrodynamic loop

The momentum loop will always perform the specified number of momentum sweeps. The hydrodynamics loop will perform another sweep if at the end of the loop the CONVERGE_ON_HYDRO variable is true, the mass residual has not converged and there are more hydrodynamic sweeps to be executed.