As discussed on the Network Solution Methodology page, AFT Impulse uses a Newton-Raphson matrix method to obtain a system level mass balance for the steady-state solution. When the Solver is finished, the continuity equation is satisfied at all branching sections. Once solved, it is a simple matter to go back and sum up all mass flows at each branch to verify that these equations are satisfied. In fact, AFT Impulse does just that.

After the Solver converges, AFT Impulse loops over each junction and adds up the inflow and outflow of mass and compares the sum to the solution tolerances. If it appears that any junction is out of tolerance, a warning is given in the output.

In the Solution Balance Summary table AFT Impulse provides additional information on the balance at each junction. This table can be displayed by selecting the option in the Output Control window General tab. Figure 1 shows an example of the Solution Balance Summary table.