Submerged jet shearing of visco-plastic sludge

We present a well-resolved numerical analysis of submerged jet mixing (sludge recirculation) of municipal sludge. Using an augmented Lagrangian algorithm, we accurately identify the position of true inactive unmixed regions. The analysis includes inertial and visco-plastic effects in laminar flow regimes. We find that inertial mixing flows are more effective in mobilizing sludge when they mix sludge that has a small yield stress. For sludge with a high yield stress, we offer other means to reduce or even fully eliminate the inactive unmixed regions, which rely on redesigning the shape of digester tank. In addition, we look at the effect of nozzle diameter and position on the efficiency of mixing.