Oscillation-induced suspension of solids in fluid and loose media

Abstract

The phenomenon under study is the behaviour of a solid body placed in some fluid adjacent to an opaque horizontal plane and oscillating perpendicular to the plane. In this condition a resultant force directed from that plane and normal to it was observed to arise. This force acts like a lifting force and tends to rapidly increase when approaching the plane. Expressions for the suspension force magnitude in relation to the plane have been derived for rotary bodies of arbitrary shape, in particular, flat, concave and convex ones. This provided possibility of assessing the height of suspension and suspending behaviour of oscillating bodies that are denser than the liquid. The inferences obtained were compared with the interaction order of two pulsing or vibrating bodies studied first by C. Bjerknes and later by other researchers, including those of the Perm Scientific School of Hydrodynamics. As shown by experiments and routine observations the effect of suspension is likely to arise in a vibrating body placed in a dry loose medium, the effect causing upward motion of the body in spite of its being denser than the medium. The physical mechanism of such a phenomenon has been put under scrutiny. This mechanism, which is believed to be a peculiar form of the segregation effect, is different from that observed in fluid suspension. The cause inducing a solid body to rise to the surface is supposed to be in that the resistance force impeding displacement of the solid body into the medium insides is greater than the force directed upwards toward the free surface. A case study is described of the similar effect produced by a medium volume oscillating about the solid body. In conclusion a general principle has been formulated on the behaviour of vibrating solid and strained bodies in the vicinity of their interfaces. The research results may be used in the theoretical calculation of turbulent suspended flows, in the theory of vibrating pumps, in explanation and assessment of pipes span bulging, especially those laid on the see bottom, – they can explain also the paradoxical unsinkability of see concretions and mystical “push up“ of heavy rock boulders to the ground surface.