Non-Newtonian fluid

A non-Newtonian fluid is a fluid in which the viscosity changes with the applied shear force. As a result, Non-Newtonian fluids may not have a well-defined viscosity.

Related Topics:
Fluid - Viscosity - Shear - Force

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Although the concept of viscosity is commonly used to characterize a material, it can be inadequate to describe the mechanical behavior of a substance, particularly non newtonian fluids. They are best studied through several other rheological properties which relate the relations between the stress and strain tensors under many different flow conditions, such as oscillatory shear, or extensional flow which are measured using different devices or rheometers. The rheological properties are better studied using tensor-valued constitutive equations, which are common in the field of continuum mechanics.

Related Topics:
Tensor - Constitutive equations - Continuum mechanics

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An inexpensive, non-toxic sample of a non-Newtonian fluid can be made quite easily. Just add corn starch to a cup of water. Add the starch in small portions and stir in slowly. When the suspension nears the critical concentration, the so called "shear thickening" property of this non-Newtonian fluid becomes apparent. The application of force from the spoon, your fingers etc. cause the fluid to behave in a more solid like fashion. If left at rest it will recover its liquid like behavior.

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Shear thickening fluids of this sort are being researched for bullet resistant body armor, useful for their ability to absorb the energy of a high velocity projectile impact but remain soft and flexible when struck at low velocities.

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Principal types of non-Newtonian fluid include:

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