Name: newtonian vs non-newtonian fluid behavior
Uploaded: 2025-02-13T15:43:08.000Z
Duration: 1 min 27 s
Channel: JoVE

Les fluides sont classés en deux types principaux : newtonien et non newtonien. Les fluides newtoniens ont une viscosité constante, et leur contrainte de cisaillement est linéairement liée à la vitesse de déformation de cisaillement.
Le comportement des fluides newtoniens est prévisible. Par exemple, l’eau, l’air, l’huile et l’essence.
Les fluides non newtoniens, cependant, présentent une viscosité variable en fonction du taux de cisaillement. Ils sont divisés en plastiques d’amincissage, d’épaississement par cisaillement et de Bingham.
Les fluides diluants par cisaillement, comme la peinture au latex et les solutions polymères, présentent une viscosité apparente réduite avec un taux de cisaillement accru, ce qui leur permet de s’écouler plus facilement lorsqu’ils sont cisaillés.
Cette propriété est utile dans des applications telles que la peinture au pinceau et l’impression à jet d’encre, où une application lisse et uniforme est requise.
Les fluides épaississants par cisaillement, tels que l’amidon de maïs dans l’eau, présentent une viscosité apparente accrue sous des taux de cisaillement plus élevés et deviennent plus résistants à l’écoulement lorsqu’ils sont agités.
Cette propriété unique les rend utiles dans les équipements de protection et les dispositifs d’amortissement.
Les plastiques Bingham, comme le dentifrice et la mayonnaise, se comportent comme des solides une fois que la limite d’élasticité est dépassée, puis s’écoulent comme des fluides, ce qui les rend idéaux pour les produits qui doivent être extrudés ou étalés.

types de fluides

Types of Fluids

Les fluides peuvent être classés en fluides newtoniens et non newtoniens en fonction de leur réponse à la contrainte de cisaillement. Les fluides newtoniens ont une relation linéaire entre la contrainte de cisaillement et le taux de déformation de cisaillement, conformément à la loi de Newton sur la viscosité. Leur viscosité reste constante quel que soit le taux de cisaillement, ce qui rend leur comportement prévisible et plus facile à analyser. Les exemples courants incluent l'eau, l'air, l'huile et l'essence.

En revanche, les fluides non newtoniens ne suivent pas la loi de Newton sur la viscosité et leur viscosité change avec des taux de cisaillement variables. Ces fluides peuvent être divisés en fluides rhéofluidifiants, rhéoépaississants et fliudes de Bingham.

Les fluides rhéofluidifiants, également appelés fluides pseudoplastiques, diminuent en viscosité avec un taux de cisaillement croissant. Les exemples incluent la peinture au latex et les solutions de polymères, qui s'écoulent plus facilement lorsqu'elles sont soumises à une force, ce qui les rend utiles dans les applications nécessitant un étalement facile sous contrainte.

Les fluides rhéoépaississants, en revanche, augmentent en viscosité avec un taux de cisaillement croissant. Un exemple courant est celui d'un mélange d'amidon de maïs et d'eau, qui devient plus résistant à l'écoulement lorsqu'il est agité, offrant une plus grande résistance sous contrainte.

Les fliudes Bingham présentent un comportement différent: ils agissent comme des solides jusqu'à ce qu'une limite d'élasticité spécifique soit appliquée, après quoi ils s'écoulent comme des fluides. Les exemples incluent le dentifrice et la mayonnaise, qui résistent à la contrainte initiale mais commencent à s'écouler une fois la limite d'élasticité dépassée. La compréhension de ces types de fluides est essentielle pour concevoir et analyser divers systèmes de fluides, des pipelines aux processus industriels, afin de garantir l'efficacité et le bon fonctionnement.

Types de fluides

Les fluides sont classés en deux types principaux : newtonien et non newtonien. Les fluides newtoniens ont une viscosité constante, et leur contrainte de cisaillement est linéairement ...

Education

Enseignement

JoVE Core

Civil Engineering

Génie civil

Unit 1

Unité 1

Fluid Properties

Propriétés des fluides

KEY TERMS AND CONCEPTS

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newtonian vs non-newtonian fluid behavior

Fluids can be grouped by how they respond to shear stress. Shear stress is a force that acts across a material, and shear strain rate describes how quickly it changes shape or flows. In this lesson, fluids are divided into Newtonian and non-Newtonian types.

Newtonian fluids follow Newton’s law of viscosity. Their shear stress changes in a linear way as the shear rate changes. That means their viscosity stays constant, so their flow is predictable and easier to analyze. Water, air, oil, and gasoline are common examples.

Non-Newtonian fluids do not follow Newton’s law of viscosity. Their viscosity changes when the shear rate changes. These fluids are often grouped into shear-thinning, shear-thickening, and Bingham plastics.

Shear-thinning fluids are also called pseudoplastic fluids. Their viscosity decreases as the shear rate increases, so they flow more easily under force. Latex paint and polymer solutions are examples, and this makes them useful when a material needs to spread easily.

Shear-thickening fluids behave in the opposite way. Their viscosity increases as the shear rate increases, so they resist flow more when they are agitated. A cornstarch-water mixture is a common example.

Bingham plastics have another pattern. They act like solids until a certain yield stress is reached. After that, they begin to flow like fluids. Toothpaste and mayonnaise are examples, and they resist initial stress before they start moving.

Knowing these fluid behaviors helps in many real systems. It supports the design and analysis of pipelines and industrial processes. It also helps engineers choose the right fluid for efficient and reliable function.

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Fluids can be grouped by how they respond to shear stress. Shear stress is a force that acts across a material, and shear strain rate describes how quickly it changes shape or flows. In this lesson, fluids are divided into Newtonian and non-Newtonian types. Newtonian fluids follow Newton’s law of viscosity. Their shear stress changes in a linear way as the shear rate changes. That means their viscosity stays constant, so their flow is predictable and easier to analyze. Water, air, oil, and...

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Learn how Newtonian and non-Newtonian fluids respond to shear stress, with examples of shear-thinning, shear-thickening, and Bingham plastics.

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civil engineering

Newtonian vs Non-Newtonian Fluid Behavior

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