A longitudinal cutaway of a rectangular basin shows particles entering at different depths, descending at their settling velocity while the water carries them toward the outlet. Adjust flow, surface area, depth, particle diameter and particle density and see whether each particle reaches the floor trench or escapes over the weir.
• A real-time 3D view with numbered, clickable parts: distributed inlet and baffle; longitudinal water cutaway; discrete settling particles; settled-solids floor and collection trench; overflow weir and clarified outlet. Scene tools include home view, focus-selected-part, auto-rotate, expand and show/hide labels, and drag-to-orbit with pinch-to-zoom. • Experiment controls: water flow (20–200 m³/h); basin surface area (40–300 m²); water depth (2–5 m); particle diameter (5–80 µm); particle density (1100–1800 kg/m³), plus a show flow/process markers toggle, pause/resume, single-step buttons (0.1 s and 1 s), a playback-speed selector and a restart trial action. • Live readouts: stokes settling velocity; surface overflow rate; ideal removal fraction; hydraulic residence time; particle Reynolds number; horizontal residence fraction. A model response curve is drawn beside the 3D view and updates as you change controls. • A Curves & measurements tab with two live charts, the model equations as written in the simulator and snapshot readouts; an Experiments tab with 2 guided presets (slow-settling particles; double the area) plus a model-verification bench, timestamped event log and copyable trial report. • A Learn & assess tab with 3 lessons (surface area governs ideal capture; depth changes travel time; stokes law has limits), a 2-question knowledge check with reset, and a written model-scope statement.
For ideal discrete settling the fraction captured is the smaller of one and the ratio of Stokes settling velocity to the surface overflow rate, where overflow rate is flow divided by surface area. A particle whose settling velocity meets or exceeds the overflow rate is removed regardless of depth, which is why doubling the area halves the overflow rate and can never reduce removal.
Depth matters differently: at fixed area and flow a deeper basin increases residence time and lengthens the distance particles must fall by the same proportion, so ideal removal is unchanged. The simulator shows hydraulic residence time and horizontal residence fraction alongside the removal value so you can see this cancellation.
Settling velocity comes from the Stokes relation for a small sphere in water at fixed viscosity, so it rises with density difference and with the square of diameter. The particle Reynolds number is displayed so you can check whether the creeping-flow assumption is reasonable for the chosen particle.
The model covers ideal spherical discrete particles only: no turbulence, flocculation or density currents. One animation second stands for ten minutes of process time, and the particle set samples inlet depths for display while the numerical removal shown is the analytical result.
It is the flow through the basin divided by its surface area, expressed as a velocity. Particles that settle faster than this rate are captured in ideal discrete settling; slower particles are only partly captured.
At fixed area and flow, a deeper basin holds the water longer but also makes particles fall farther. The two effects cancel, so ideal removal depends on area and flow rather than depth.
Stokes settling velocity scales with the square of particle diameter, so doubling the diameter makes a particle settle about four times faster, all else equal. Very small particles may not be captured at all at a given overflow rate.
Stokes law assumes creeping flow around a sphere, which holds at low particle Reynolds number. The simulator displays that number so you can see when larger or denser particles push the assumption beyond its range.