عنوان مقاله [English]
In this study, the impact of spherical hydrophobic particles on an air-water interface was analyzed experimentally. The aim of this study is to obtain a critical impact velocity in which the hydrophobic particle remains on the liquid surface so that it penetrates completely at higher velocities than the critical velocity. A mathematical model was developed based on energy balance to predict the critical velocity. The Teflon particles of diameter 3-5 mm were used. Distilled water with a density of 1000.71 kg/m3 was used as the fluid. Particle falls into the fluid were captured by using a high-speed video camera with the rate of 4500 fps. For Teflon spherical hydrophobic particles, two floatation and penetration regimes were observed from experiments. After processing of sequential images, the motion of a particle inside the fluid was obtained and for the first time, the maximum penetration depth, rebound depth, rebound height and the pinch off depth were determined for each particle and it was found that, at critical velocities, particle penetration is associated with oscillations, and at higher velocities than the critical number, the number of oscillations is decreased. The dependence of maximum penetration depth on drop height was studied and it was found that with increasing drop height, the maximum penetration depth is also increased. Also, the effect of particle size on critical velocity was investigated and it was observed that with increasing the particle size, the critical velocity is decreased. In addition, the particle velocity and the velocity of the three-phase contact line were plotted at critical conditions. The developed mathematical model was also compared with the experimental observations, and it was found that there is a good agreement with the measured values.