Monday, August 23, 2010

Non-Newtonian Fluids

Refer to equation 5.4 on page 164, the viscous force in a Newtonian fluid, planar geometry.

For a fluid to be considered a Newtonian fluid, it must follow that the force is proportional to that equation. However, when a fluid doesn't follow this principle, then we are required to call them a Non-Newtonian fluid. Now, I'm sure we've all heard of this phenomena before (the naturally easiest example of one is the mixture of corn flour and water). What is really cool about Non-Newtonian fluids is the way in which force acts upon the system.
The application of a small force leaves us in a laminar flow region, where we can move the liquid around as a liquid does. When we move up to a large force however, there doesn't become such a thing is turbulent flow, there instead becomes a solid.
In an Non-Newtonian fluid, there is a non-linear relation existing between shear and strain stress, and a viscosity coefficient cannot be defined.
Common examples of these fluids are oobleck (cornflour and water), glurch (borax and white glue), ketchup, shampoo, paint, blood and silicone polymer suspensions.


  1. So that;s why you can stir cornflour and water quite easily, but if you punch it it's like hitting a brick.

    I love that trick.

  2. Indeed. Also I forgot to attach a few links to this blog, so I shall put them here.
    The first is from Big Bang theory, where they have a bit of fun with oobleck on a speaker.
    This second one is actually me doing the charleston on oobleck (not easily done I might mention)
    For more, also view the videos uploaded on youtube by username "youngphysicists" as these are actually videos uploaded by UQ's physics club PAIN.