What is Non-Newtonian fluid?

A non-Newtonian fluid is a fluid whose viscosity is variable based on applied stress or force. The most common everyday example of a non-Newtonian fluid is cornstarch dissolved in water. The behaviour of Newtonian fluids like water can be described exclusively by temperature and pressure. However, the physical behaviour of non-Newtonian fluid depends on the forces acting on it from second to second.

Interesting properties of Non-Newtonian fluids

If you punch a bucket full of non-Newtonian fluid such as cornstarch, the stress introduced by the incoming force causes the atoms in the fluid to rearrange such that it behaves like a solid. Your hand will not go through. If you shove your hand into the fluid slowly, however, it will penetrate successfully. If you pull your hand out abruptly, it will again behave like a solid, and you can literally pull a bucket of the fluid out of its container in this way. Non-Newtonian fluids help us understand the wide variety of fluids that exist in the physical world.

A search for non-Newtonian fluid on the internet brings up some interesting results. When combined with an oscillating plate, non-Newtonian fluids demonstrate other unusual properties, like protruding “fingers” and holes that persist after creating them. An oscillating plate applies stress on a periodic basis, rapidly changing the viscosity of the fluid and putting it in an odd middle ground between a liquid and a solid. At the same time, there are examples wherein one can place a bowl of cornstarch near a vibrating speaker to see the interesting patterns that are created on the surface of the mixture.

Physics of Non-Newtonian fluids

To define it scientifically, a non-Newtonian fluid is a fluid whose flow properties are not described by a single constant value of viscosity. Many polymer solutions and molten polymers are non-Newtonian fluids, as are many commonly found substances such as ketchup, starch suspensions, paint, and shampoo. In a Newtonian fluid, the relation between the shear stress and the strain rate is linear, the constant of proportionality being the coefficient of viscosity. In a non-Newtonian fluid, the relation between the shear stress and the strain rate is nonlinear, and can even be time-dependent. Therefore, a constant coefficient of viscosity cannot be defined.

Conclusion

This experiment demonstrates an interesting property of fluids that we see in everyday life. These properties are useful for certain applications. For example, this property helps when one wants the paint to flow readily off the brush when it is being applied to the surface being painted, but not to drip excessively. Another relevant fluid property in this class is evident by a ketchup which will not come out of the bottle until you stress it by shaking. This helps to control the flow of the ketchup.

A practical application for non-Newtonian fluids may be in body armor of the future. Since such fluids are usually flexible, they would allow soldiers to move freely when not under attack. But if confronted with a speeding bullet, they would quickly harder, performing like traditional armor. More research is of course necessary to see if non-Newtonian fluids are suitable for similar applications, but until then, it’s sure fun to play with.

This is an activity that supports state physical science standards, engages students, and opens the imagination to future applications. This activity is appropriate for all elementary levels with the follow-up varying at the teacher’s discretion for her scholastic level.

Uses of Non-Newtonian Fluid

This experiment demonstrates an interesting property of fluids that we see in everyday life. These properties are useful for certain applications. For example, this property helps when one wants the paint to flow readily off the brush when it is being applied to the surface being painted, but not to drip excessively. Another relevant fluid property in this class is evident by a ketchup which will not come out of the bottle until you stress it by shaking. This helps to control the flow of the ketchup.

A practical application for non-Newtonian fluids may be in body armor of the future. Since such fluids are usually flexible, they would allow soldiers to move freely when not under attack. But if confronted with a speeding bullet, they would quickly harder, performing like traditional armor. More research is of course necessary to see if non-Newtonian fluids are suitable for similar applications, but until then, it’s sure fun to play with.

This is an activity that supports state physical science standards, engages students, and opens the imagination to future applications. This activity is appropriate for all elementary levels with the follow-up varying at the teacher’s discretion for her scholastic level.

Applications of Non-Newtonian fluids

  • Liquid Armor
  • Sport shoes
  • Viscous couplings
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