The flux flow method is a graphical method based on plotting the solids flux against the solids concentration. Typically, for this analysis the solids flux is calculated by using Kynch analysis on an interface versus time curve from the observation of batch settling of sludge/solids.
The video below provides a general introduction to the flux flow design method.
The graph below shows the batch flux curve (left) and the continuous flux curve (right) with the key operating lines. The key design parameters can be varied to examine the effect on the settler design and area.