Predominantly unidirectional rotation of a viscous liquid with a free boundary

The problem is considered on a periodical of time motion of a viscous liquid bordering on a solid body and a gas. The liquid is affected by oscillatory influences which have no predominant direction in space. The new hydromechanical effect is revealed which consists in that the free parts of the hydro-mechanical system — liquid layers — perform unidirectional stationary rotational motion with the background of oscillations.