Active control for suppression of swirling sloshing in a circular tank.

This research aimed to develop an active control technique to suppress a swirling sloshing in a circular tank by injecting air bubbles in a microcomputer controlled manner. Using three air bubble injectors located on the bottom of the test tank at a circumferential pitch of 120 degrees, air bubbles were injected into the swirling sloshing water at a controlled timing and duration. The effects of timing and duration of air bubble injection on suppressing the swirling sloshing were investigated and the following major results were obtained: (1) Air bubble injection into a swirling sloshing water was markedly effective on suppressing the sloshing, (2) but the timing of air bubble injection was the most important parameter, that was at the instance when the sloshing wave was ascending from the lowest position to the equilibrium. (3) A small amount of air, equivalent to 0.4% of the water contained in the tank, was sufficient to suppress the swirling sloshing.