Characterization of Droplet Collision and Breakup on a Hemispherical Target

In the present work, simulation results are obtained to characterize the liquid drop impingement and pinch-off mechanism on a hemispherical substrate. Several critical stages are anticipated during the entire impact process. Various nondimensional parameters, including the diameter ratio (D_h/D_o), contact angle (θ), Ohnesorge number (Oh), Bond number (Bo), and Weber number (We), are implemented in the characterization of fluidic mechanisms involved in collision, spreading, and detachment with the solid stationary target. We have furnished numerical phase contours to comprehend qualitatively the fluidic behavior of liquid mass during the entire collision cycle. We have characterized the maximum deformation factor (β_f, max) by considering the above-mentioned pertinent quantities. There is a discernible increasing trend in β_f, max as We gradually increases for a given θ and D_h/D_o. Again, β_f, max constantly reduces as the value of Oh grows for a given value of We and D_h/D_o. Again, the value of entrapped gaseous volume (V*) constantly drops down as the surface becomes hydrophilic to superhydrophobic for a given value of We. We have strived to generate a regime plot on the Oh–We plane for different D_h/D_o and contact angles to address the distinguished zones based on the entrapped gaseous bubble. Efforts are also made to develop a correction for β_f, max. The developed correlation strongly agrees with the simulated predictions to within ±7%. Lastly, a theoretical model is devised to forecast the deformation factor, demonstrating near-match with the numerical outcomes.