Cavitation

Definition

Whenever a liquid accelerates — through an impeller eye, a valve vena contracta, or an orifice — its static pressure falls. If the pressure drops below the vapor pressure, the liquid vaporises locally. As the flow then decelerates and pressure recovers above the vapor pressure, the bubbles implode, focusing their energy onto nearby surfaces. That pressure recovery is what separates cavitation from flashing: in flashing the downstream pressure stays below vapor pressure, so the vapor persists and never collapses; in cavitation the recovery is what drives the implosion and the damage.

Engineering context

For pumps, cavitation risk is managed through NPSH — keeping NPSHa above NPSHr with an adequate margin. For control valves and orifices, the risk depends on how far the pressure dips at the vena contracta relative to vapor pressure, which is set by the pressure drop taken across the device and the downstream pressure. FluidFlow anchors valve cavitation to the pressure recovery factor F_L used in the ISA 75.01.01 control valve sizing method. Because both cases depend on the whole connected system, cavitation checks belong in the network model: FluidFlow evaluates suction conditions at every pump and the pressure profile through every control valve as part of the steady-state solution, flagging at-risk equipment.

Related definitions

NPSH · Pump curve · Control valve Cv/Kv · Vapor pressure · Backpressure

See it in FluidFlow

Spot cavitation risk early. FluidFlow evaluates NPSH margins and valve pressure profiles across your system as part of the steady-state solution.