Plain English Meaning
When air flows through a narrow spot, it speeds up and its pressure drops. The tighter the squeeze, the faster the flow and the lower the pressure at that point.
Full Definition
The drop in pressure that occurs when a moving fluid (such as air) passes through a narrowed section of a passage. As the fluid speeds up to get through the constriction, its static pressure falls.
Context Anchor
Seen in instrument-system discussions, especially when an alternate static source uses cabin air instead of the normal outside pressure source.
Derivation
Named after Giovanni Battista Venturi, an 18th-century Italian physicist who studied how fluids behave when forced through a constriction. Knowing it's a person's name, not a Latin term, helps avoid hunting for a hidden meaning in the word.
Why Pilots Care
It explains how certain blockages produce erroneous airspeed and altitude indications during flight.
Analogy
Similar to water pressure falling inside a garden hose when you partially cover the open end with your thumb.
Grounding Statement
Picture squeezing a garden hose: the water shoots out faster where the hose is pinched. Air does the same thing -- it speeds up through the narrow spot, and its pressure drops while it's there.
Intuition Check
The venturi effect is not a separate suction force. It is lower pressure caused by faster-moving air.
Example Sentence 1
The shape of the wing uses the venturi effect to lower the pressure on top, which helps create lift.
Example Sentence 2
Understanding the venturi effect helps pilots recognize why an altimeter may overread after a static port blockage.