LE13271 - Everyone who has ever observed the surface ripples that form in a simple vibrating cup of water served in an airplane or a train has unconsciously performed the experiment carried out for the first time in 1831 by Faraday. It consists in the rhythmical vertical shaking of a recipient filled with water and ever since Faradays first observations the developing surface waves are known as Faraday Waves. Only a few researchers have paid attention to another phenomenon which seems to be linked to these surface waves: the induced movements of tiny particles added to the fluid. In this paper, we determine for the first time the whole surface velocity field and its statistics using a technique called Particle Image Velocimetry (PIV). Surprisingly the energy spectra of this fluid flow show characteristics typical for 2-dimensional turbulence which is an important approximation for natural systems such as currents in the ocean or circulations in the atmosphere. In contrast to three-dimensional turbulence it includes the possibility of passing energy from small to large spatial scales, a process which explains a seemingly contradiction: the creation of large structures such as eddies when stirring only happens on much smaller scales.
