Fundamentals of Non-Newtonian Liquid Flow on Surfaces

摘要

Polymers, which are added to liquids to control the liquid's dissemination properties, also alter the rheological properties of the liquid. The polymer solutions exhibit such non-Newtonian properties as shear thinning and normal stress, which are not included in the usual Newtonian fluid model. This report evaluates theoretically how these non-Newtonian properties affect the spreading of liquid drops on ideal surface. Using the lubrication approximation, the spread rates and size doubling times are numerically calculated. Results show that shear thinning and normal stresses are considerably less important than the zero-shear-rate viscosity, and affect the spreading only during the initial spreading period, during which the drop is less than twice its original size. The viscosity's shear dependence and the normal stresses cause the size doubling time to change by less than 10% of the size doubling time of a similar drop of Newtonian liquid. Spreading on a tilted surface is also examined and its is found to be accountable by the addition of a translational motion to the spreading motion on the previously considered horizontal surface.