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Newtonian fluids are fluids where the viscous stresses are proportional to the local strain rate, meaning the forces are proportional to the rates of change of the fluid's velocity. For Newtonian fluids to also be isotropic, the viscosity tensor reduces to two real coefficients describing resistance to shear deformation and compression/expansion. While no real fluid perfectly fits the definition, many common liquids and gases like water and air can be treated as Newtonian for practical calculations under ordinary conditions. Newtonian fluids are the simplest mathematical models of fluids that account for viscosity and are named after Isaac Newton who first derived the relationship between shear strain rate and shear stress for such fluids.

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20 views1 page

Construction & Building Technology

Newtonian fluids are fluids where the viscous stresses are proportional to the local strain rate, meaning the forces are proportional to the rates of change of the fluid's velocity. For Newtonian fluids to also be isotropic, the viscosity tensor reduces to two real coefficients describing resistance to shear deformation and compression/expansion. While no real fluid perfectly fits the definition, many common liquids and gases like water and air can be treated as Newtonian for practical calculations under ordinary conditions. Newtonian fluids are the simplest mathematical models of fluids that account for viscosity and are named after Isaac Newton who first derived the relationship between shear strain rate and shear stress for such fluids.

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Dash AssxEzio
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Newtonian fluid

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In continuum mechanics, a fluid is said to be Newtonian if the viscous stresses that arise
from its flow, at every point, are proportional to the local strain rate — the rate of change of
its deformation over time.[1] [2][3] That is equivalent to saying that those forces are
proportional to the rates of change of the fluid's velocity vector as one moves away from the
point in question in various directions.

More precisely, a fluid is Newtonian only if the tensors that describe the viscous stress and
the strain rate are related by a constant viscosity tensor that does not depend on the stress
state and velocity of the flow. If the fluid is also isotropic (that is, its mechanical properties
are the same along any direction), the viscosity tensor reduces to two real coefficients,
describing the fluid's resistance to continuous shear deformation and continuous compression
or expansion, respectively.

Newtonian fluids are the simplest mathematical models of fluids that account for viscosity.
While no real fluid fits the definition perfectly, many common liquids and gases, such as
water and air, can be assumed to be Newtonian for practical calculations under ordinary
conditions. However, non-Newtonian fluids are relatively common, and include oobleck
(which becomes stiffer when vigorously sheared), or non-drip paint (which becomes thinner
when sheared). Other examples include many polymer solutions (which exhibit the
Weissenberg effect), molten polymers, many solid suspensions, blood, and most highly
viscous fluids.

Newtonian fluids are named after Isaac Newton, who first derived the relation between the
rate of shear strain rate and shear stress for such fluids in differential form.

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