Energy transition of a sphere launched upward from stationary water toward air

Abstract

In a present experiment, a solid sphere with a density of 2600 kg/m³ and diameter of 25.4 mm was launched vertically upward in water toward the air-water interface. The submergence depth was changed and the launch velocity was adjusted so that the Reynolds number of the sphere immediately after passing the air-water interface was almost equal at each submergence depth. The energy ratio E_p/E_k was defined as the ratio of the kinetic energy E_k of the sphere immediately after it passed through the air-water interface to the potential energy E_p when the sphere reached the maximum displacement position. E_p/E_k decreased when the submergence depth was H/d < 3. However, it had a constant value of E_p/E_k ~ 0.57 when the submergence depth was H/d ≥ 3. In addition, when the submergence depth was H/d ≥ 3, the ratio of each energy became similar immediately after passing through the water surface. This indicated that each energy distribution had reached the equilibrium state.