See entrainment

Entrainment

Entrainment may refer to:* Air entrainment, the intentional creation of tiny air bubbles in concrete* Brainwave entrainment, the practice of entraining one's brainwaves to a desired frequency...

 for other types.

Entrainment is the movement of one fluid

Fluid

In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

 by another.

One fluid moving in another can push or pull the other along with it. Eductors or eductor-jet pumps are an excellent example. They are used onboard many ships to pump flooded out compartments in the event of an accident. Seawater is pumped to the eductor and forced through a jet. Any fluid at the inlet of the eductor is carried along to the outlet and up and out of the compartment. Eductors can pump out whatever can flow through them, including water, oil, and small pieces of wood. Another example is the pump-jet

Pump-jet

A pump-jet, hydrojet, or water jet, is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal pump and nozzle...

, which is used for marine propulsion. Jet pumps are also used to circulate reactor coolant in several designs of boiling water reactors (BWRs).

In power generation, this phenomenon is used in steam jet air ejectors to maintain condenser vacuum by removing non-condensible gases from condenser.

Entrainment due to laminar velocity shear or turbulent diffusion of momentum is also important in laminar and turbulent jets and plumes

Plume (hydrodynamics)

In hydrodynamics, a plume is a column of one fluid or gas moving through another. Several effects control the motion of the fluid, including momentum, diffusion, and buoyancy...

.