Motion of a Solid Sphere Launched Vertically Upward toward Water Surface and the Behavior of Air-Water Interface Induced by the Sphere

Abstract

To investigate the variation in a sphere's motion and the behavior of the air-water interface induced by the sphere, a solid sphere is launched vertically upward in water toward the air-water interface. Four spheres with different densities ρ_p were studied: a stainless steel sphere (ρ_p = 7930 kg/m³), an alumina sphere (ρ_p = 3900 kg/m³), a Teflon sphere (ρ_p = 2180 kg/m³), and a Duracon sphere (ρ_p = 1360 kg/m³). By experimentally visualizing the sphere motion in water, their launch velocity can be set with high accuracy. When a sphere passes through the air--water interface, it makes the interface more complex and entrains water. Additionally, spheres with a small value of ρ_p were demonstrated to not always vertically collide with the air--water interface.