Experimental and numerical study on air cores for cylindrical tank draining

An air core is generated during draining after rotating cylindrical tanks filled with liquid. Air cores have a complex flow structure including rotational motion and a change in the free surface shape. In addition, the generation and extinction of air cores are dependent on the initial rotating speed, the dimensions of the tank, and the liquid materials. This phenomenon is usually detected in various applications for different fields such as the flow in the tundish discharging process of the smelting process, the liquid fuel system of rockets, from the suction of pumps, and so on. In this study, the flow structures including the drain time, the change in the free surface shape, velocity field, and vorticity distributions are numerically and experimentally investigated. Both the numerically and experimentally results were in good agreement with each other with respect to the drain time.