The decision at stake
The box was about to be assembled with the straight floor of the original design. The question was not whether the equipment worked, but where it would wear first and whether that point could be reached during a shift maintenance window. A liner in the wrong place forces the line to stop for a change.
Geometry and mesh
The box, the inlet launder and the first metre of the receiving conveyor were modelled. The support structure was left out: it does not change the velocity field. Polyhedral mesh with refinement in the impact zone and a resolved boundary layer on the floor. The sensitivity study ran on three levels at refinement ratio r = 2.
Physics and assumptions
Multiphase flow with a free surface; slurry treated as a Newtonian fluid equivalent to the operating concentration. It was stated from the start that the model does not resolve particle segregation: that is what the Particle line is for.
Convergence
Residuals below 1e-4 in continuity and momentum, with the mass balance closed under 0.5 %. The cut-off criterion was declared before running, together with the acceptance criterion against measurement.
Validation
Three control points against site measurement: discharge jet velocity, slurry depth and flow per launder. The largest deviation was 4.5 %, within the ±5 % criterion agreed with the client.
Conclusion and limits
Redesigning the floor moved the impact zone to a face reachable from the maintenance platform. The conclusion holds for the measured flow range; outside it the impact point moves and the model has to be run again.