The third principle of the Pumps family, alongside the rotodynamic and the positive-displacement ones. Under the Hydraulic Institute classification, these are kinetic pumps with no rotating mechanical element: the energy that moves the liquid comes not from a rotor or piston, but from an external agent — a motive fluid/gas (ejector, air lift, hydraulic ram) or, in the one case with no motive fluid at all, an electromagnetic field (the electromagnetic pump, below).
The in-scope types:
- Ejector / eductor (jet pump) — a high-velocity motive-fluid jet creates low pressure (Venturi effect) that entrains and pressurizes the drawn liquid. No moving parts; used for priming, deep wells and process vacuum.
- Air lift — compressed air injected at the base of a column lowers the mixture's mean density, which rises by buoyancy. Ideal for abrasive or solids-laden liquids (nothing is in contact).
- Hydraulic ram — harnesses the kinetic energy of a water stream (water hammer) to lift a fraction of the flow to great height, with no external power.
- Electromagnetic pump — an electromagnetic field directly drives liquid metals (sodium, lead-bismuth — reactor circuits and metallurgy). No moving parts, no sealing.
Classification boundaries (taxonomic honesty): regenerative (peripheral), vortex (recessed impeller) and disc (viscous drag, Tesla-type) pumps are sometimes listed as "special effect", but they have a rotor — the Hydraulic Institute treats them in the kinetic branch next to the rotodynamic ones. The "flexible hose pump" is the peristaltic — it lives in Positive Displacement.
Common advantage: robustness and low cost (few or no moving parts). The price: low efficiency versus rotodynamic pumps. (per-type handbooks in Phase 1 — they require their own anatomy)