INFLUENCE OF SURFACE WETTABILITY ON THE PROCESS OF OBLIQUE WATER ENTRY OF SPHERE

The influence of surface wettability on the evolution process of inclined water entry cavitation and dynamic characteristics of the sphere is studied in order to further understand the influence of wettability on water entry process and provide theoretical basis for water entry phenomena in various cases. Based on the experimental platform of observation, acquisition and measurement of cavitation morphology and the numerical simulation method, the evolution laws of splashing and cavitation during water entry of hydrophilic and hydrophobic spheres are analyzed, and the influence of surface wettability of spheres on dynamic characteristics during water entry of spheres at different speeds is discussed. The results show that there are obvious differences in the evolution and dynamic characteristics of spatter and cavitation of different surface wettability spheres during water entry. At the same velocity, the three phase contact point of the hydrophilic sphere is much higher than that of the hydrophobic sphere, while the splashing height is lower than that of the hydrophobic sphere, but the difference decreases with the increase of the water entry speed. With the increase of water entry velocity, the hydrophilic sphere experiences three closure modes successively: no cavitation, shallow closure and surface closure, while the hydrophobic sphere only shows deep closure and surface closure. But, With the increase of water entry velocity, the influence of surface wettability on the cavity evolution process gradually decreases, and there is no difference between the two when the speed increases to 11.25 m/s. At the same time, it is found that the total flow resistance coefficient of the water entering cavity is 49.94% lower than that of the non-water entering cavity at the same velocity. The volume of the void generated by the hydrophilic sphere is smaller, the additional mass force brought by the void is also smaller, and the drag reduction effect is better.