The everyday perception of Newtonian viscosity The normal perception of the level of viscosity of Newtonian liquids by untrained persons is described by Steven's gencral power-law of psycho-physical cognition For viscosity states,the estimates are approximately proportional to the square root of the real numerical value. e.g.n(water)=1 mPa.s,n(oil)=100 mPa.s,and n(comn syrup)=106 mPas Then oil would be preceive as 10 times more viscous than water and com syrup would be preceive as 1000 times more viscous than water. Stevens,S.S and Guiro,M,Science 144,1157-8 1964. The limit of Newtonian behaviour 10 103 1031010 102 Shear rate,/s Flow curves for a series of silicone oils Note the ian behaviour at a shear stress of around 2000 Pa VISCOMETRY 'It mistake to thcorise before one has data'Arthur Conan Doyle introduction Viscometry is the science of the measurement of viscosity.Such viscometric lly hav to do with g either a force F or a velocity Vat a with ained test i se of this liquid to either which is als m contact of the used for this purpose include tubes,parallel plates,cone-an plate arrangeme and co the presen interferes with the local lquid microstructure,giving apparent p will be discussed in detail later. 66 The everyday perception of Newtonian viscosity The normal perception of the level of viscosity of Newtonian liquids by untrained persons is described by Steven’s general power-law of psycho-physical cognition: For viscosity states, the estimates are approximately proportional to the square root of the real numerical value. e.g. η(water) = 1 mPa.s, η(oil) = 100 mPa.s, and η(corn syrup) = 106 mPa.s Then oil would be preceive as 10 times more viscous than water and corn syrup would be preceive as 1000 times more viscous than water. Stevens, S.S. and Guirao, M, Science 144, 1157-8. 1964. The limit of Newtonian behaviour