Water entry dynamics of spheres considering the surface topography effect
The phenomenon of moving bodies into water widely exists in nature and ocean engineering,such as various aquatic organisms walking on water,large ships sailing on the sea,and torpedoes traveling underwater.It is imperative to construct air cavities on the surface of the moving body to achieve underwater drag reduction.In this study,spheres with different microstructure area occupancies are prepared by controlling the height of the corrosion solution.Afterward,the multiphase flow process and drag reduction characteristics of the obtained spheres with different microstructure area occupancies are analyzed for vertical water entry.In addition,the deflection mechanism of an asymmetric water entry gas cavity from the energy perspective is presented.The findings reveal that the trajectory of the asymmetrically microstructured sphere is shifted laterally due to the momentum transfer imbalance in the horizontal direction during the water entry process;moreover,the no-slip boundary condition on the surface is transformed into a free-slip boundary condition at the gas-liquid interface when air-cavity entrapment takes place in the water entry of the asymmetrically microstructured sphere,which reduces the fluid drag force by 82.9％-93.4％.This study offers a novel approach for regulating the trajectory of an underwater moving body using an asymmetric air cavity generated by modulating the surface topography of spheres.
surface topography effectincoming air cavityhydrodynamicsdrag reduction
万方数据
维普
