While the CFX-Solver is running, the default setting is to plot the data as a
                function of Accumulated Time Step. However, you may choose to
                view the data as a function of any available variable.
For example, you may choose to plot an important monitored quantity as a function
                of residual level. The existing residual plot provides information on the exact
                convergence level, while this plotting feature gives another way to determine how
                far you need to converge the solution, by combining residual information with
                monitored quantities. For example, if you were to plot Mass Averaged
                    Outlet Total Pressure vs. Mass Residual, you
                would see how quickly this important quantity stabilizes as a function of the
                residual convergence level. You may then set a residual target for future runs that
                causes the CFX-Solver to stop when the established residual levels are sufficient for
                the "important monitored quantity".
You can change the variable that is plotted on the X axis for any specific plot as follows:
Right-click the plot you want to modify (see Convergence History Plots and User Point Plots) and select Monitor Properties from the shortcut menu.
On the Range Settings tab, set Plot Data By to
Specified Variableand select the variable you want to use as the X axis variable.