Non-Newtonian Drops Spreading on a Flat Surface

Abstract

The objective of this study is to develop a computational model that accurately describes the dynamic behavior of a non-Newtonian power-law film formed after a drop impinges on a flat surface. The non-Newtonian drop deposition and spreading process is described by a model based on one developed for Newtonian liquids. The effects of variations in non-Newtonian liquid rheological parameters, such as Ren (the non-Newtonian Reynolds number), n (the flow behavior index), and We (the Weber number), are studied in detail. Results show that a reduction in the viscous forces results in enhanced spreading of the film followed by a more rapid recession. An increase in surface tension results in reduced spreading of the film, followed by a more rapid recession. Model predictions of film diameter as a function of time were larger than corresponding experimental values obtained as part of this study. However, the discrepancy never exceeded 21%, demonstrating that the model accurately predicts the phenomena of interest. This comparison also shows that the results are in best agreement for large non-Newtonian Reynolds numbers and small non-Newtonian Ohnesorge numbers (We/Ren).