Multiphase smoothed particle hydrodynamics modeling of two drops impacting on a solid surface

This work investigates the dynamics of dual-drop impact on a solid surface, encompassing both simultaneous and nonsimultaneous side-by-side impact of equal-sized drops, as well as successive impact of unequal-sized drops. Numerical simulations are performed using smoothed particle hydrodynamics method to capture the associated complex fluid dynamics. For side-by-side impact, the influences of the Weber number, horizontal spacing, and vertical spacing on liquid film merging are examined. The impact dynamics are characterized using three dimensionless parameters: the spread factor of the merged liquid film, the dimensionless central liquid sheet height, and dimensionless time. The results indicate that both the maximum spread factor and the dimensionless central sheet height increase with the Weber number. The spacings significantly affect the impact outcomes: horizontal spacing primarily influences the spread factor, whereas vertical spacing governs the morphology, inclination angle, and height of the central liquid sheet. For successive impact, simulations are conducted to analyze the effects of leading and trailing drop diameters, vertical spacing, Weber number, wall temperature, and ambient pressure. The conditions influencing the spread factor, apex height, crown height, and rebound height are investigated. The results demonstrate that an increase in the trailing drop's diameter enhances the spread factor, while the crown height diminishes with reduced vertical spacing. Furthermore, increasing the vertical spacing elevates the crown height but reduces the spread factor for different Weber numbers of the trailing drop. A higher trailing drop Weber number increases the spread factor. An increase in wall temperature reduces the spread factor and elevates the apex height, while elevated ambient pressure suppresses rebound and prolongs residence time. Based on these results, predictive models for dual-drop impact dynamics are proposed.