This simulator magnifies a pump's impeller eye and entrance passage to show vapor bubbles forming where local pressure drops below the liquid's vapor pressure, then collapsing as pressure recovers through the impeller and volute. Change source temperature, suction pressure, source elevation and suction resistance, and watch available suction head, a synthetic NPSH3 reference, bubble severity and an illustrative erosion sample respond live.
• A real-time 3D cutaway workbench (temperature-controlled suction vessel, magnified impeller eye and entrance passage, curved rotating impeller channels, pressure-recovery passage, illustrative erosion sample coupon, head/vibration observation station, and discharge return boundary) with home view, focus-selected-part, show full enclosure, exploded view, auto-rotate, expand and hide-labels scene tools. • Experiment controls: water temperature (5–90 °C), source surface absolute pressure, source surface elevation above inlet datum, suction resistance coefficient, reference pump speed, delivery static head and delivery system resistance sliders, plus pause/resume, single-step and 1 s-step buttons, four playback speeds, and dedicated 'Heat source to 80 °C' / 'Cool source to 25 °C' / 'Clear illustrative exposure' actions. • A Curves & measurements analysis tab with two live charts (degraded head vs. ideal head; NPSHa vs. synthetic NPSH3), the underlying NPSHa/NPSH3/exposure equations, and snapshot readouts (predicted flow, vapor pressure, available head above vapor, NPSH3, available/NPSH3 ratio, degraded and ideal head, head-reduction percentage, bubble-envelope severity, accumulated illustrative exposure). • An Experiments tab with four guided fixtures (cool-water baseline, hot suction source, restricted suction, recovery after exposure showing the erosion sample does not reset on its own) and a Model verification bench with a timestamped event log and copyable trial report. • A Learn & assess tab with four guided lessons, a knowledge-check quiz with reset, and a written model-scope statement linking to a cavitation reference.
As liquid accelerates into the impeller eye, local pressure drops. If it falls to the liquid's vapor pressure — which the simulator computes from an Antoine-style approximation that rises sharply with temperature — vapor bubbles form. As those bubbles are carried into the pressure-recovery passage toward the volute, rising pressure collapses them again, and repeated collapse near a surface is the mechanism behind cavitation erosion, illustrated here by a progressively pitted sample coupon.
The available margin above vapor pressure, NPSHa = (Psurface − Pvapor)/(ρg) + zsource − Ks·Q², is compared against a synthetic NPSH3 reference curve that scales with the square of pump speed. The model's illustrative envelope begins reducing head at a ratio of 1.3 and reaches 3% head reduction at a ratio of 1.0 — mirroring the industry NPSH3 head-drop test convention, but as an explicit teaching approximation.
The erosion sample's pitting reflects an accumulated illustrative 'exposure' — the time-integral of a normalized bubble-severity indicator — that does not disappear when suction conditions improve, mirroring how real cavitation damage is cumulative and irreversible even after the cause is corrected. Only the explicit 'Clear illustrative exposure' action resets it, which the recovery-after-exposure experiment demonstrates directly.
This model fixes liquid density at 1000 kg/m³, uses synthetic (not manufacturer) pump and NPSH3 curves, and makes no claim about real erosion rate, acoustic/vibration amplitude, or component life. NPSH3 itself denotes a specific 3% head-drop test criterion — meeting a chosen margin above it is not a universal guarantee against bubble formation, noise or long-term damage.
Vapor cavities form directly from the liquid itself when local pressure — typically at the impeller eye, where the liquid accelerates — drops to or below the liquid's vapor pressure at its current temperature. It is not outside air leaking in or solid particulate matter.
No. NPSH3 is a specific test-derived reference corresponding to a 3% head-drop criterion, not a guarantee of bubble-free or damage-free operation. Some bubble formation and erosion risk can exist below a manufacturer's recommended margin above NPSH3, which is why applications typically specify additional margin.
A liquid's vapor pressure rises sharply with temperature. Since available suction margin is measured as pressure above vapor pressure, a higher vapor pressure directly reduces that margin even if every other condition (source pressure, elevation, losses) stays the same — shown in the hot-suction-source experiment.
No, and the simulator deliberately models this: its illustrative accumulated exposure indicator does not decrease when conditions improve, mirroring how real cavitation erosion is cumulative and irreversible. Only an explicit reset action clears the illustrative exposure total.