Non-Newtonian fluid facts for kids

Mechanics

Laws Conservation of mass Conservation of momentum Conservation of energy Entropy inequality Solid mechanics Solids Stress · Deformation Compatibility Finite strain · Infinitesimal strain Elasticity (linear) · Plasticity Bending · Hooke's law Failure theory Fracture mechanics Frictionless/Frictional Contact mechanics Fluid mechanics Fluids Fluid statics · Fluid dynamics Surface tension Navier–Stokes equations Viscosity: Newtonian, Non-Newtonian Rheology Viscoelasticity Smart fluids: Magnetorheological Electrorheological Ferrofluids Rheometry · Rheometer Scientists Bernoulli · Cauchy · Hooke Navier · Newton · Stokes

Paint is a non-Newttonian fluid. In non-Newtonian fluids viscosity varies with the stress they are exposed to. Paint which is under low stress will behave differently from paint that is under high stress. When a surface with paint turned from horizontal to vertical orientation, it will be exposed to stress from gravitation. Therefore, instead of slipping along the surface, it forms very large drops, that are very dense and almost solid. This creates the great effect that can be seen in the figure.

A non-Newtonian fluid is a thixotropic fluid which changes its viscosity when the forces on it change.

Other flow properties may also be affected. Most commonly viscosity of such fluids is not independent of the shear rate or the shear rate history. Examples of such fluids are blood, quicksand and certain components of cement. Many lubricants, ketchup, certain forms of dough and pudding also have this property.

The other kind of fluids that do not show this behavior are called Newtonian fluids.

It is very simple to make a non-Newtonian fluid at home. All one needs is water and cornstarch. Mix these two ingredients together at a rate of one part cornstarch and one and a half parts water. That makes a non-Newtonian fluid.

Related pages

• Mudslide
• Avalanche

Images for kids

• 

  Demonstration of a non-Newtonian fluid at Universum in Mexico City

• 

  Oobleck on a subwoofer. Applying force to oobleck, by sound waves in this case, makes the non-Newtonian fluid thicken.

• 

  Slime flows under low stresses but breaks under higher stresses