07-09-09, 01:53 AM
I figured it would be pretty uncommon, but D H just wrote in another thread that cream is one too. I am disheartened. Could someone tell me, given 100 every day most commonly found and used liquids, how many of them are non-newtonian?
Just as there is no such thing as a truly ideal gas, I would suspect that there is no such thing as a truly Newtonian fluid. Look at a fluid with enough precision over a wide range of conditions and somewhere you will find a deviation from the Newtonian fluid model at some nth decimal place in some parameter.
For non-Newtonian fluids the Newtonian model isn't even close to correct. The Newtonian fluid model is close to correct for many (most?) fluids because the departure from this model is small / limited to a small domain. We can pretend that the fluid is Newtonian because ignoring the departures doesn't change the predicted results by a measurable amount.
07-09-09, 06:09 PM
Ah. I should've known this. Thank you for the timely and very good answer.