Editing Fluid dynamics (section)

===Newtonian versus non-Newtonian fluids===
[[File:Flow around a wing.gif|thumb|Flow around an [[airfoil]]]]

All fluids, except [[superfluids]], are viscous, meaning that they exert some resistance to deformation: neighbouring parcels of fluid moving at different velocities exert viscous forces on each other. The velocity gradient is referred to as a [[strain (materials science)|strain rate]]; it has dimensions {{math|''T''{{isup|−1}}}}. [[Isaac Newton]] showed that for many familiar fluids such as [[water]] and [[Earth's atmosphere|air]], the [[stress (physics)|stress]] due to these viscous forces is linearly related to the strain rate. Such fluids are called [[Newtonian fluids]]. The coefficient of proportionality is called the fluid's viscosity; for Newtonian fluids, it is a fluid property that is independent of the strain rate.

[[Non-Newtonian fluid]]s have a more complicated, non-linear stress-strain behaviour. The sub-discipline of [[rheology]] describes the stress-strain behaviours of such fluids, which include [[emulsion]]s and [[slurries]], some [[viscoelasticity|viscoelastic]] materials such as [[blood]] and some [[polymer]]s, and ''sticky liquids'' such as [[latex]], [[honey]] and [[lubricants]].<ref>{{cite journal |last1=Wilson | first1=DI |title=What is Rheology? |journal=Eye |date=February 2018 |volume=32 |issue=2 |pages=179–183 |doi=10.1038/eye.2017.267 |pmid= 29271417 |pmc=5811736}}</ref>