hydrodynamics 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) a ...

, a clapotis (from

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

for "lapping of water") is a non-breaking

standing wave In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect ...

pattern, caused for example, by the reflection of a traveling surface

wave In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (re ...

train from a near vertical shoreline like a

breakwater Breakwater may refer to: * Breakwater (structure), a structure for protecting a beach or harbour Places * Breakwater, Victoria, a suburb of Geelong, Victoria, Australia * Breakwater Island, Antarctica * Breakwater Islands, Nunavut, Canada * Br ...

seawall A seawall (or sea wall) is a form of coastal defense constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation ...

or steep

cliff In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on co ...

. The resulting ''clapotic'' wave does not travel horizontally, but has a fixed pattern of nodes and antinodes. These waves promote erosion at the toe of the wall, and can cause severe damage to shore structures. The term was coined in 1877 by

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

and

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

Joseph Valentin Boussinesq who called these waves 'le clapotis' meaning "the lapping". In the idealized case of "full clapotis" where a purely

monotonic In mathematics, a monotonic function (or monotone function) is a function between ordered sets that preserves or reverses the given order. This concept first arose in calculus, and was later generalized to the more abstract setting of order ...

incoming wave is completely reflected

normal Normal(s) or The Normal(s) may refer to: Film and television * ''Normal'' (2003 film), starring Jessica Lange and Tom Wilkinson * ''Normal'' (2007 film), starring Carrie-Anne Moss, Kevin Zegers, Callum Keith Rennie, and Andrew Airlie * ''Norma ...

to a solid vertical wall, the standing

wave height In fluid dynamics, the wave height of a surface wave is the difference between the elevations of a crest and a neighboring trough. ''Wave height'' is a term used by mariners, as well as in coastal, ocean and naval engineering. At sea, the te ...

is twice the height of the incoming waves at a distance of one half wavelength from the wall. In this case, the circular orbits of the water particles in the deep-water wave are converted to purely linear motion, with vertical velocities at the antinodes, and horizontal velocities at the nodes. The standing waves alternately rise and fall in a mirror image pattern, as

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acce ...

is converted to

potential energy In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors. Common types of potential energy include the gravitational potenti ...

, and vice versa. In his 1907 text, ''Naval Architecture'',

Cecil Peabody Cecil Hobart Peabody (1855 – 1934) was an American mechanical engineer, born on August 9 in Burlington, Vermont. He was very influential in the development of the Mechanical Engineering Department and in founding the Department of Naval Architec ...

described this phenomenon:

Related phenomena

True clapotis is very rare, because the depth of the water or the precipitousness of the shore are unlikely to completely satisfy the idealized requirements. In the more realistic case of partial clapotis, where some of the incoming wave energy is dissipated at the shore, the incident wave is less than 100% reflected, and only a partial standing wave is formed where the water particle motions are elliptical. This may also occur at sea between two different wave trains of near equal wavelength moving in opposite directions, but with unequal amplitudes. In partial clapotis the wave envelope contains some vertical motion at the nodes. When a wave train strikes a wall at an oblique angle, the reflected wave train departs at the

supplementary angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles a ...

causing a

cross-hatch Hatching (french: hachure) is an artistic technique used to create tonal or shading effects by drawing (or painting or scribing) closely spaced parallel lines. (It is also used in monochromatic representations of heraldry to indicate what the t ...

ed wave interference pattern known as the ''clapotis gaufré'' ("waffled clapotis"). In this situation, the individual crests formed at the intersection of the incident and reflected wave train crests move parallel to the structure. This wave motion, when combined with the resultant vortices, can erode material from the seabed and transport it along the wall, undermining the structure until it fails. Clapotic waves on the sea surface also radiate infrasonic microbaroms into the atmosphere, and

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

signals called microseisms coupled through the ocean floor to the solid Earth. Clapotis has been called the bane and the pleasure of

sea kayaking A sea kayak or touring kayak is a kayak developed for the sport of paddling on open waters of lakes, bays, and the ocean. Sea kayaks are seaworthy small boats with a covered deck and the ability to incorporate a spray deck. They trade off the ma ...

References

External links

* {{Good article Wave mechanics Coastal engineering Water waves

Related phenomena

See also

References

Further reading

External links