Which principle drives foam concentrate through an inline foam eductor into the water stream?

Which principle drives foam concentrate through an inline foam eductor into the water stream?

• A. Bernoulli
• B. Venturi
• C. Coanda effect
• D. Turbine mixing

Answer: (B)

The Venturi effect is what drives foam concentrate into the water stream in an inline foam eductor. When water moves through the eductor’s constricted throat, it speeds up, and the static pressure in that region drops. That pressure drop creates suction that pulls foam concentrate from its supply into the flowing water, where they mix to form foam. The eductor’s design—a constricted nozzle and mixing chamber—uses this pressure differential to set the foam-to-water ratio. Bernoulli’s principle underpins why faster flow lowers pressure, but the term Venturi specifically describes the nozzle configuration that produces the suction in foam eductors. The Coanda effect isn’t the mechanism here, and turbine mixing refers to a mechanical mixing action rather than how the concentrate is entrained into the water stream.

The Venturi effect is what drives foam concentrate into the water stream in an inline foam eductor. When water moves through the eductor’s constricted throat, it speeds up, and the static pressure in that region drops. That pressure drop creates suction that pulls foam concentrate from its supply into the flowing water, where they mix to form foam. The eductor’s design—a constricted nozzle and mixing chamber—uses this pressure differential to set the foam-to-water ratio.

Bernoulli’s principle underpins why faster flow lowers pressure, but the term Venturi specifically describes the nozzle configuration that produces the suction in foam eductors. The Coanda effect isn’t the mechanism here, and turbine mixing refers to a mechanical mixing action rather than how the concentrate is entrained into the water stream.