In an Australian experiment the physicists studied effects of a simple object that causes waves in fluid. They found that if it vibrates slow, the objects on the surface move away from the source of vibration (that's a well known phenomenon). But when the vibrations from the frequency about 30 Hz, the object begins to move to the source.

I can imagine that just like the forces on an object on a carpet when I'm pulling it up causes it to stay on place. But why do the objects (of whatever size) tend to move towards the source when the freqency of the vibration is high (and not only stay on the place they were before)?


1 Answer 1


Let's focus on the frequency

  • Faster frequency means from the point of view of a ball on the surface just a more smooth surface
  • Faster frequency means also faster changes in pressure of the water

For lower frequencies, a ball adjust to the moving surface of the water Just like the ocean waves , the mass of water is simply being pushed apart from the "source". The ball loses more energy (it decelarates more) to "climb" a top is higher than the "extra speed" it gains when sliding into a hollow.

For higher frequencies, the high-frequency vibrating water is comparable with a very smooth surface Higher frequencies make more rapid changes in the pressure of the fluid The vibrating cylinder is creating (more) vacuum when lifting up from the water

Stabilizing forces (moving for higher frequencies):

Capillary effect, Gravity, Friction

Moving forces (stabilizing for higher frequencies): Hydraulic pressure, creating a stream towards the source trying to balance the vacuum created by the cylinder.

According to this hypothesis, it shoudln't work on an open sea.


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