Name: how depth changes fluid pressure
Uploaded: 2023-09-22T11:49:33.000Z
Duration: 1 min 14 s
Channel: JoVE

La pression est définie comme l’amplitude de la force par unité de surface. Dans le cas d’un fluide incompressible, la force peut être exprimée en termes de poids spécifique ou de densité du fluide.
Considérons quatre points dans l’eau. La pression est la même pour tous les points situés à la même profondeur de la surface, mais moins à faible profondeur. La pression augmente linéairement avec la profondeur de la surface.
Selon la loi de Pascal, l'intensité de la pression en un point donné dans un fluide statique incompressible est la même dans toutes les directions.
Supposons un élément fluide infinitésimal cunéiforme de largeur unitaire. La force de chaque côté est exprimée comme le produit de la pression et de la surface.
Lorsque le liquide est au repos, la somme des composantes horizontales et verticales des forces doit être nulle.
En prenant les composantes horizontales et en utilisant des relations trigonométriques, les équations sont simplifiées pour obtenir px égal à ps.
De même, en considérant les composantes verticales, les équations sont simplifiées pour obtenir py égal à ps. 
Ainsi, la pression en tout point est la même dans toutes les directions.

<ol>
	<li>Hibbeler, R.C. (2016). Mécanique du génie : Statique. Quatorzième édition, New Jersey : Pearson. p. 512.</li>
</ol>

pression des fluides

En génie mécanique, la pression des fluides joue un rôle essentiel dans la conception de systèmes qui utilisent l'écoulement des liquides, tels que les systèmes hydrauliques, les pompes et les vannes. Lors de la conception de ces systèmes, les ingénieurs doivent veiller à ce qu'ils puissent supporter les forces créées par la pression des fluides afin d'éviter les dommages ou les défaillances. Selon la loi de Pascal, un fluide au repos générera une pression égale dans toutes les directions. Cette pression est mesurée comme une force par unité de surface, et sa magnitude dépend de la masse volumique ou densité de fluide et de la profondeur du point de mesure par rapport à la surface du fluide. Nous pouvons exprimer cette relation mathématiquement comme p = ρgz, où ρ est la densité du fluide, g est l'accélération due à la gravité et z est la profondeur. Il convient de noter que l'équation, telle que mentionnée ci–dessus, est valable pour les fluides incompressibles, tels que la plupart des liquides, mais pas pour les gaz, dont la densité change considérablement avec la température et la pression. Pour comprendre comment cette équation s'applique aux liquides, considérons trois points situés à l'intérieur de l'eau. À la même profondeur par rapport à la surface, la pression est identique pour les trois points. Cependant, la pression est plus faible à faible profondeur. La pression augmente linéairement avec la profondeur à mesure que l'on s'éloigne de la surface.

Pression des fluides

En génie mécanique, la pression des fluides joue un rôle essentiel dans la conception de systèmes qui utilisent l’écoulement de liquide, tels que les systèmes hydrauliques, les pompes et ...

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Fluid Pressure

how depth changes fluid pressure

Fluid pressure changes with depth in liquids used in engineering systems. It matters in hydraulic systems, pumps, and valves, where the forces from moving and resting fluid must be considered to prevent damage or failure.

For a fluid at rest, Pascal’s law says the pressure is equal in all directions. Pressure is force per unit area. Its size depends on the fluid’s specific weight, or mass density, and on how deep the measurement point is below the fluid surface.

This relationship can be written as p = ρgz. In this equation, ρ is fluid density, g is the acceleration due to gravity, and z is depth. The equation applies to incompressible fluids, such as most liquids, but not to gases, because gas density can change greatly with temperature and pressure.

The pattern is easy to see in water. If three points are at the same depth, their pressure is the same. A point closer to the surface has lower pressure. As depth increases, pressure rises in a linear way.

How Depth Changes Fluid Pressure

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key terms and concepts

Explore how fluid pressure changes with depth, why Pascal’s law matters, and how the equation p = ρgz describes pressure in liquids like water.

How Depth Changes Fluid Pressure | JoVE K12

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How Depth Changes Fluid Pressure

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