# Bernoulli vs. Venturi?

**URL:** <https://boards.straightdope.com/t/bernoulli-vs-venturi/198362>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [August 29, 2003, 3:22am UTC](https://boards.straightdope.com/t/bernoulli-vs-venturi/198362 "2003-08-29T03:22:28Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\
**Post date:** [August 29, 2003, 3:22am UTC](https://boards.straightdope.com/t/bernoulli-vs-venturi/198362/1 "2003-08-29T03:22:28Z")

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In [a classic column on gas pump shutoff](http://www.straightdope.com/classics/a1_263.html), Cecil refers to the Bernoulli effect as being the tendency of a stream of fluid to draw in surrounding fluid. I thought this was the Venturi effect, and that the Bernoulli effect was that a deflected stream had a lower density than a direct stream (i.e., under & over an airplane wing, which turns out not to be nearly as responsible for flight as we’ve been taught but that’s a whole nother post).

Can some fluid/aerodynamics wizard straighten me out on this?

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**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\
**Post date:** [August 29, 2003, 4:30am UTC](https://boards.straightdope.com/t/bernoulli-vs-venturi/198362/2 "2003-08-29T04:30:33Z")

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Bernoulli’s equation is responsible for the Venturi effect. Bernoulli says that the various energies in a flow are constant. When you pass fluid through a narrowed opening, it has to speed up, so the pressure goes down.