A 2D cross-section view of the same Lapple cyclone model as the 3D lab: a mixed batch of particles, drawn from a lognormal size spread around your chosen median size, spirals down the outer vortex to be captured or reverses up the inner vortex to escape — driven by the real grade-efficiency curve plotted live beside it.
Lapple's (1951) cut-diameter and grade-efficiency model for a reverse-flow cyclone: how inlet velocity, cyclone body diameter and particle size together set the diameter at which a particle has a 50% chance of capture, and how sharply efficiency falls off below it.
Pick a geometry preset, drag the inlet velocity and median particle size sliders, and watch both the cross-section spiral and the grade-efficiency curve respond immediately. "New batch" redraws a fresh random sample at the current settings.
Because grade efficiency is a smooth S-curve rather than a hard cutoff, real cyclones always let a small fraction of particles above the cut diameter through and capture a small fraction below it — which is exactly the spread this simulation's lognormal batch is built to show.