In
fluid dynamics
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) an ...
, wave–current interaction is the interaction between
surface gravity waves and a
mean flow In fluid dynamics, the fluid flow is often decomposed into a mean flow and deviations from the mean. The averaging can be done either in space or in time, or by ensemble averaging.
Example
Calculation of the mean flow may often be as simple as the ...
. The interaction implies an exchange of energy, so after the start of the interaction both the waves and the mean flow are affected.
For depth-
integrated and
phase
Phase or phases may refer to:
Science
*State of matter, or phase, one of the distinct forms in which matter can exist
*Phase (matter), a region of space throughout which all physical properties are essentially uniform
* Phase space, a mathematic ...
-
average
In ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of the numbers divided by how many numbers are in the list (the arithmetic mean). For example, the average of the numbers 2, 3, 4, 7, ...
d flows, the quantity of primary importance for the
dynamics of the interaction is the wave
radiation stress tensor.
Wave–current interaction is also one of the possible mechanisms for the occurrence of
rogue wave
Rogue waves (also known as freak waves, monster waves, episodic waves, killer waves, extreme waves, and abnormal waves) are unusually large, unpredictable, and suddenly appearing surface waves that can be extremely dangerous to ships, even to lar ...
s, such as in the
Agulhas Current
The Agulhas Current () is the western boundary current of the southwest Indian Ocean. It flows south along the east coast of Africa from 27°S to 40°S. It is narrow, swift and strong. It is suggested that it is the largest western boundary curren ...
. When a
wave group
The group velocity of a wave is the velocity with which the overall envelope shape of the wave's amplitudes—known as the ''modulation'' or ''envelope (waves), envelope'' of the wave—propagates through space.
For example, if a stone is thr ...
encounters an opposing current, the waves in the group may pile up on top of each other which will propagate into a rogue wave.
Classification
identifies five major sub-classes within wave–current interaction:
* interaction of waves with a large-scale current
field
Field may refer to:
Expanses of open ground
* Field (agriculture), an area of land used for agricultural purposes
* Airfield, an aerodrome that lacks the infrastructure of an airport
* Battlefield
* Lawn, an area of mowed grass
* Meadow, a grass ...
, with slow – as compared to the
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
–
two-dimensional
In mathematics, a plane is a Euclidean (flat), two-dimensional surface that extends indefinitely. A plane is the two-dimensional analogue of a point (zero dimensions), a line (one dimension) and three-dimensional space. Planes can arise as s ...
horizontal variations of the current fields;
* interaction of waves with small-scale current changes (in contrast with the case above), where the horizontal current varies suddenly, over a
length scale
In physics, length scale is a particular length or distance determined with the precision of at most a few orders of magnitude. The concept of length scale is particularly important because physical phenomena of different length scales cannot aff ...
comparable with the wavelength;
* the combined wave–current motion for currents varying (strongly) with depth below the
free surface
In physics, a free surface is the surface of a fluid that is subject to zero parallel shear stress,
such as the interface between two homogeneous fluids.
An example of two such homogeneous fluids would be a body of water (liquid) and the air in ...
;
* interaction of waves with
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
; and
* interaction of ship waves and currents, such as in the ship's
wake
Wake or The Wake may refer to:
Culture
*Wake (ceremony), a ritual which takes place during some funeral ceremonies
*Wakes week, an English holiday tradition
* Parish Wake, another name of the Welsh ', the fairs held on the local parish's patron s ...
.
See also
*
generalized Lagrangian mean
In continuum mechanics, the generalized Lagrangian mean (GLM) is a formalism – developed by – to unambiguously split a motion into a mean part and an oscillatory part. The method gives a mixed Eulerian–Lagrangian description for the flow ...
*
rip current
A rip current, often simply called a rip (or misleadingly a ''rip tide''), is a specific kind of water current that can occur near beaches with breaking waves. A rip is a strong, localized, and narrow current of water which moves directly away ...
Footnotes
References
*
*
*
*
*
*
*
Physical oceanography
Water waves
{{fluiddynamics-stub