Analysis of complex fluid discharge from consumer dispensing bottles using rheology and flow visualization

Abstract Complex fluids, such as gels, shampoos, and creams, are ubiquitous in the consumer product industry. However, little information is available on their discharge from consumer packaging, often resulting in a considerable heel, i.e., the residual waste material after the discharge process is complete. Here, we used rheological analysis and particle image velocimetry (PIV) to investigate the discharge of rheologically different fluids from a dispensing bottle provided with a modified hand pump. The fluids were described in terms of rheological parameters established by fitting rheometric data with the Carreau equation. The effect of operational parameters was also studied, which included the dip tube diameter, suction pressure, and volumetric flow rate. The data were also analyzed in terms of the dimensionless region of interest (ROI), which captures the relative “high-velocity” region in the fluid during the discharge process and is measured directly using PIV. Both rheological and operational parameters affect the heel at the end of the discharge process. The results presented here enable predicting the heel either by measuring ROI as in the case of transparent fluids and packages or by making use of the heel correlation with operational and rheological parameters also established in this work. Graphical abstract