Stokes drift

Stokes drift

[¦stōks ‚drift]
(fluid mechanics)
The drift of particles in a gravity wave, which arises from the fact that particle velocities are periodic with a mean which is not zero.
References in periodicals archive ?
British, German and French scientists said along with surface ocean currents and wind, the so-called "Stokes drift" was also of central importance for calculating how debris from the aircraft drifted before making landfall.
He said: "For any application where surface drift is studied, Stokes drift should be included to provide more precise tracking results."
From their point of view, in addition to surface ocean currents and wind, the so-called Stokes drift is also of central importance for the drift of objects in the uppermost layer of the ocean surface.
In Section 5 the steady Eulerian velocity is corrected through Stokes drift. This produces the steady Lagrangian velocity which is important because: (i) it is the Lagrangian velocity that is observed in experiments; (ii) it is the Lagrangian velocity that is invariant under the change of the frame of reference from the one fixed in the oscillating sphere to the one fixed in space.
It is well-known that in oscillatory flows the observed averaged Lagrangian velocity differs from the Eulerian velocity by the term known as Stokes drift. The velocity observed in the experiments is the velocity of fluid particles, that is, the Lagrangian velocity.
Attempts have been made to overcome the inconsistency between the recorded data and Ekman theory by using numerical modelling including the depth-varying eddy viscosity (Madsen 1977; Huang 1979) and by complementing the physical background of the Ekman layer description with dynamic processes like the buoyancy flux, Stokes drift, etc.
One parameter describes the effect of the Stokes drift (Phillips 1977) and two other parameters characterize the vertical profile of velocity below the layer influenced by the Stokes drift.
In terms of wave spectrum, the Stokes drift can be estimated with the relationship bellow:
From this reason the Stokes drift was estimated using the mass transport relationship from the second order theory (Lakshmi and Clayson 2000):
A fluid particle may experience an additional "Stokes drift" (named for the 19th-century English physicist Sir George Stokes) due to spatial variations in the magnitude of the oscillatory tidal current.
For a current rotating clockwise (as is usual for Northern Hemishpere currents) the Stokes drift will be in the opposite direction to this.
Stokes drifted in off the left flank unchallenged and scored with a 25–yard piledriver.