Non-Newtonian Fluids
Fluids whose shear viscosity changes depending on applied shear rate, stress magnitude, or shear history.
Governing formula
τ = K (du / dy)^n (n ≠ 1)
SI unit
Pa·s (Apparent Viscosity η)
In depth
Unlike Newtonian fluids (where viscosity is constant), non-newtonian fluids exhibit shear-thinning (pseudoplastic, e.g. paint), shear-thickening (dilatant, e.g. cornstarch Oobleck), or Bingham plastic yield stress behavior.
Examples in the real world
Shear-thickening Oobleck solidifying instantly upon high-impact shock, and shear-thinning ketchup flowing when shaken.