Spreading of water-in-oil emulsion drop on oleophilic surface.

This article focuses on the three-dimensional numerical simulation of water-in-oil (W/O) emulsion drop spreading on a solid oleophilic surface, emphasizing the roles of high-shear rate rheology and dispersed phase microdroplets. Using rotational rheometry and drop impact viscometry (DIV), the study models emulsions with Herschel–Bulkley shear-thinning behavior and incorporates vortex flow effects via turbulence models (standard k–ε and Langtry–Menter k–ω SST LM). Results show that vortex flow significantly influences maximum spreading at around 30 wt.% dispersed phase concentration and higher impact velocities, with vorticity near the boundary layer increasing fourfold as velocity rises. The empirical expression β_max = 0.82(We/Oh)^0.15 for predicting maximum spreading factor is validated, though it underestimates spreading by about 10% for non-Newtonian emulsions. These findings have practical implications for optimizing processes such as inkjet printing and spray cooling, where accurate modeling of emulsion rheology under high shear rates is critical.