Fluid speed increases when the fluid is forced through a narrow or restricted area. The increased speed results in a reduction in pressure. The underbody venturi is shaped to create a low pressure area between the road and chassis which creates downforce.
as a fluid (such as air) flows through a constriction (like a mountain pass), the speed increases and the pressure drops
Increase in the speed of flow of gasses or liquids caused by a constriction or bend in the containing duct.
The increase in speed and reduction in pressure of a gas as it passes through a restricted orifice, such as air through an aspirator, or carburetor.
The speedup of air through a constriction due to the pressure rise on the upwind side of the constriction and the pressure drop on the downwind side as the air diverges to leave the constriction.
The increase in the velocity of a fluid stream as it passes through a constriction in a channel, pipe, or duct. Calculated by the Continuity Equation, or = VA VA where is the volumetric flow rate, is the Area of flow, and is the fluid velocity. Because does not change, as gets smaller then must increase.
The principle that fluid moving through a smaller area will move at a higher velocity than the same amount of water moving through a larger area. As an example, floodwater moving through a narrow opening such as Wallula Gap* was moving much faster, with significantly more erosive power, than the water above or below the gap.
In an internal combustion engine, a relative vacuum is created in the cylinders by the downward strokes of the pistons. Because atmospheric pressure is higher than the low-pressure area in each cylinder, it rushes through the carburetor to equalize the low-pressure area in the cylinders. On its way to the cylinders, however, air must pass through the venturi. The venturi constricts the inrushing air column, then allows it to widen back out to the throttle bore diameter. This incoming air has a certain pressure. To get through the venturi, it must speed up, which lowers its pressure as it passes through the venturi. This change in pressure is known as the venturi effect. yVenturi vacuumzƒxƒ“ƒ`ƒ…ƒŠ‚É”¶‚·‚é'ሳBƒGƒ“ƒWƒ“‚̉ñ“]”‚É”ä—á‚·‚éB
The Venturi effect is a special case of Bernoulli's principle, in the case of fluid or air flow through a tube or pipe with a constriction in it. The fluid must speed up in the restriction, reducing its pressure and producing a partial vacuum via the Bernoulli effect. It is named after Giovanni Battista Venturi, (1746–1822), an Italian physicist.