  Faraday waves are capillary ripples that form on the surface of a fluid being
subject to vertical shaking. Although it is well known that the form and shape
of the waves pattern depend on driving amplitude and frequency, only recent
studies discovered the existence of a horizontal velocity field at the surface,
called Faraday flow, which exhibits attributes of two-dimensional turbulence.
However, despite the increasing attention towards the inverse energy flux in
the Faraday flow and other not strictly two-dimensional systems, very little is
known about the velocity fields developing beneath the fluid surface. In this
study planar velocity fields are measured by means of particle image
velocimetry (PIV) with high spatial and temporal resolution on the water
surface and below it. A sudden drop in velocity is observed immediately below
the water surface, such that at 5 mm below the water surface the mean absolute
velocities are already about 6.5 times smaller than the surface velocity.
Additionally, the flow structures below the surface are found to comprise much
larger spatial scales than those on the surface. These large structures are
also found to be slow and temporarily persistent, as proven by analysing the
autocorrelation of the velocity fields in time.
