The Great Green Wave of Existence

Surfing is dead, long live Kelly Slater's swampy green wave

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Next the surfer wipes off some speed to settle in for the tube and you set your watch to count how long you stay covered up by the breaking wave. Tubes equals power in the natural world. A lot of energy is involved, usually in shallow water. The danger coefficient is high, making it the nirvana of many surfers. A bit more turning on the uniform face and there you go.

If the crowd was going wild, the microphones were a long way away. Creator Kelly Slater and stars like Felipe Toledo say the uncontrollable factors have been removed, leaving only skill. The wavepool delivers bucketloads of skill. We are, after all, watching the cream of the crop. But, please, sport is so much more than this stripped-down, triple-distilled, heartless drop of muscle coordination. It is drama, it is crowds, it is face-to-face competition. Wherever you look — daytime TV, talent shows — we watch chaos and uncertainty, manufactured or otherwise.

This was the first confirmed measurement of a freak wave, more than twice as tall and steep as its neighbors with characteristics that fell outside any known wave model. The wave was recorded by all of the sensors fitted to the platform [28] and it caused enormous interest in the scientific community. Statoil researchers presented a paper in which collated evidence that freak waves were not the rare realizations of a typical or slightly non-gaussian sea surface population Classical extreme waves but rather they were the typical realizations of a rare and strongly non-gaussian sea surface population of waves Freak extreme waves.

This was a scientific research vessel and was fitted with high quality instruments. The subsequent analysis determined that under severe gale force conditions with wind speeds averaging 21 metres per second These were some of the largest waves recorded by scientific instruments up to that time. The authors noted that modern wave prediction models are "known" to significantly under-predict extreme sea states for waves with a 'significant' height H s above 12 metres The analysis of this event took a number of years, and noted that "none of the state-of-the-art weather forecasts and wave models—the information upon which all ships, oil rigs, fisheries, and passenger boats rely—had predicted these behemoths.

This finding was widely reported in the press which reported that "according to all of the theoretical models at the time under this particular set of weather conditions waves of this size should not have existed". Most popular texts on oceanography up until the mid s such as that by Pirie made no mention of rogue or freak waves. It is now proven via satellite radar studies that waves with crest to trough heights of 20 metres Thus acknowledgement of the existence of rogue waves despite the fact that they cannot plausibly be explained by even state-of-the-art wave statistics is a very modern scientific paradigm.

Professor Akhmediev of the Australian National University , one of the world's leading researchers in this field, has stated that there are about 10 rogue waves in the world's oceans at any moment. Rogue waves may also occur in lakes. A phenomenon known as the "Three Sisters" is said to occur in Lake Superior when a series of three large waves forms. The second wave hits the ship's deck before the first wave clears. The third incoming wave adds to the two accumulated backwashes and suddenly overloads the ship deck with tons of water.

The phenomenon is one of various theories as to the cause of the sinking of the SS Edmund Fitzgerald on Lake Superior in November Optical sciences group, Australian National University [43]. Serious studies of the phenomenon of rogue waves only started about 20—30 years ago and have intensified since about One of the remarkable features of the rogue waves is that they always appear from nowhere and quickly disappear without a trace.

Recent research has suggested that there could also be 'super-rogue waves' which are up to five times the average sea-state. Rogue waves has now become a near universal term given by scientists to describe isolated large amplitude waves, that occur more frequently than expected for normal, Gaussian distributed, statistical events. Rogue waves appear to be ubiquitous in nature and are not limited to the oceans.

They appear in other contexts and have recently been reported in liquid helium, in nonlinear optics and in microwave cavities. It is now universally accepted by marine researchers that these waves belong to a specific kind of sea wave, not taken into account by conventional models for sea wind waves. Researchers at the Australian National University have also recently proven the existence of rogue wave holes , an inverted profile of a rogue wave.

In maritime folk-lore, stories of rogue holes are as common as stories of rogue waves. They follow from theoretical analysis but had never been proven experimentally. In the ANU published research confirming the existence of rogue wave holes on the water surface observed in a water wave tank. On a smaller scale, kayakers call unpredictable 'exploding waves' caused by wave interaction " clapotis ".

Because the phenomenon of rogue waves is still a matter of active research, it is premature to state clearly what the most common causes are or whether they vary from place to place. The areas of highest predictable risk appear to be where a strong current runs counter to the primary direction of travel of the waves; the area near Cape Agulhas off the southern tip of Africa is one such area; the warm Agulhas Current runs to the southwest, while the dominant winds are westerlies. However, since this thesis does not explain the existence of all waves that have been detected, several different mechanisms are likely, with localised variation.

Suggested mechanisms for freak waves include the following:. Rogue waves can result from the constructive interference dispersive and directional focusing of elementary 3D waves enhanced by nonlinear effects. The spatio-temporal focusing seen in the NLS equation can also occur when the nonlinearity is removed. In this case, focusing is primarily due to different waves coming into phase, rather than any energy transfer processes. Further analysis of rogue waves using a fully nonlinear model by R. Gibbs brings this mode into question, as it is shown that a typical wavegroup focuses in such a way as to produce a significant wall of water, at the cost of a reduced height.

A rogue wave, and the deep trough commonly seen before and after it, may last only for some minutes before either breaking, or reducing in size again. Apart from one single rogue wave, the rogue wave may be part of a wave packet consisting of a few rogue waves. Such rogue wave groups have been observed in nature. Bahram Jalali and other researchers at UCLA studied microstructured optical fibers near the threshold of soliton supercontinuum generation and observed rogue wave phenomena. After modelling the effect, the researchers announced that they had successfully characterized the proper initial conditions for generating rogue waves in any medium.

It should be noted that many of these encounters are only reported in the media, and are not examples of open ocean rogue waves. Often, in popular culture, an endangering huge wave is loosely denoted as a rogue wave , while it has not been and most often cannot be established that the reported event is a rogue wave in the scientific sense — i. She was lost with all crew and the wreck has never been found. The only evidence found was the starboard lifeboat which was recovered from floating wreckage some time later.

The pins had been bent back from forward to aft, indicating the lifeboat hanging below it had been struck by a wave that had run from fore to aft of the ship which had torn the lifeboat from the ship. At the time of the inquiry, the existence of rogue waves was considered so statistically unlikely as to be near impossible. The loss of the MV Derbyshire during Typhoon Orchid south of Japan with the loss of all crew marked a turning point for ship design. The Derbyshire was an ore-bulk-oil combination carrier built in At 91, gross register tons, she was—and remains—the largest British ship ever to have been lost at sea.

The wreck was found in June The survey team deployed a remotely operated vehicle to photograph the wreck. A private report was published in which prompted the British government to reopen a formal investigation into the sinking. The British government investigation included a comprehensive survey by the Woods Hole Oceanographic Institution which took , pictures of the wreck during two surveys. The formal forensic investigation concluded that the ship sank because of structural failure and absolved the crew of any responsibility.

Most notably, the report determined the detailed sequence of events that led to the structural failure of the vessel. A third comprehensive analysis was subsequently done by Douglas Faulkner, professor of marine architecture and ocean engineering at the University of Glasgow.

About The Green Wave

His highly analytical and scientific report published in examined and linked the loss of the MV Derbyshire with what he called the emerging body of scientific evidence regarding the mechanics of freak waves. Professor Faulkner concluded that it was almost certain that Derbyshire would have encountered a wave of sufficient size to destroy her.

Faulkner's conclusions have not been refuted in the more than 15 years since they were first presented as of Indeed, subsequent analysis by others has corroborated his findings. Faulkner's finding that the Derbyshire was lost because of a rogue wave has had widespread implications on ship design. There is however no evidence that his recommendations have yet been adopted as of In an extreme wave was recorded impacting the Admiralty Breakwater, Alderney in the Channel Islands.

This breakwater is exposed to the Atlantic Ocean. The peak pressure recorded by a shore-mounted transducer was kPa which corresponds to a pressure of This pressure far exceeds almost any design criteria for modern ships and this wave would have destroyed almost any merchant vessel. The deck cargo hatches on the Derbyshire were determined to be the key point of failure when the rogue wave washed over the ship. The design of the hatches only allowed for a static pressure of less than two metres of water or The forensic structural analysis of the wreck of the Derbyshire is now widely regarded as irrefutable.

In addition fast moving waves are now known to also exert extremely high dynamic pressure. It is known that plunging or breaking waves can cause short-lived impulse pressure spikes called Gifle peaks. Evidence of failure by this mechanism was also found on the Derbyshire. Very few ship-wrecks have ever been fully investigated. The most recent bulk-carrier loss on the open seas to have been subjected to thorough investigation as at March was the UK-owned M.

Derbyshire , which sank in Its entire crew of forty-four, all British citizens, perished.

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It took 14 years of pressure from the British public and a privately funded expedition to locate the wreck before a formal remote-camera search and investigation was done by the British government. At least a couple of hundred bulk carriers have been lost since and none have been properly investigated.

Nine other vessels broke completely in two. Causes of the remaining forty losses are unknown. The scenario is very simple: What happens next depends on the structure of the vessel. Professor Faulkner who did the forensic independent analysis of the loss of the M. Derbyshire explains why this is such a problem for bulk carriers. He states that "It is quite possible that some of the many unexplained heavy weather losses of bulk carriers may have been caused by hatch cover or coaming failures because fore end plunging due to flooding of large holds can be rapid.

They tend to bury into them. Derbyshire was the quite inadequate strength of her cargo hatch covers to withstand the forces of Typhoon Orchid. These types vary in wavelength , and include radio waves , microwaves , infrared radiation , visible light , ultraviolet radiation , X-rays and gamma rays. Waves are described by a wave equation which sets out how the disturbance proceeds over time. The mathematical form of this equation varies depending on the type of wave.

Further, the behavior of particles in quantum mechanics are described by waves. In addition, gravitational waves also travel through space, which are a result of a vibration or movement in gravitational fields. A wave can be transverse , where a disturbance creates oscillations that are perpendicular to the propagation of energy transfer, or longitudinal: While mechanical waves can be both transverse and longitudinal, all electromagnetic waves are transverse in free space.

A single, all-encompassing definition for the term wave is not straightforward. A vibration can be defined as a back-and-forth motion around a reference value. However, a vibration is not necessarily a wave. An attempt to define the necessary and sufficient characteristics that qualify a phenomenon as a wave results in a blurred line. The term wave is often intuitively understood as referring to a transport of spatial disturbances that are generally not accompanied by a motion of medium occupying this space as a whole. In a wave, the energy of a vibration is moving away from the source in the form of a disturbance within the surrounding medium Hall , p.

However, this motion is problematic for a standing wave for example, a wave on a string , where energy is moving in both directions equally, or for electromagnetic e.

There are water waves on the ocean surface; gamma waves and light waves emitted by the Sun; microwaves used in microwave ovens and in radar equipment; radio waves broadcast by radio stations; and sound waves generated by radio receivers, telephone handsets and living creatures as voices , to mention only a few wave phenomena.

It may appear that the description of waves is closely related to their physical origin for each specific instance of a wave process.

Rogue wave

For example, acoustics is distinguished from optics in that sound waves are related to a mechanical rather than an electromagnetic wave transfer caused by vibration. Concepts such as mass , momentum , inertia , or elasticity , become therefore crucial in describing acoustic as distinct from optic wave processes. This difference in origin introduces certain wave characteristics particular to the properties of the medium involved. For example, in the case of air: Rayleigh waves , dispersion ; and so on.

Other properties, however, although usually described in terms of origin, may be generalized to all waves. For such reasons, wave theory represents a particular branch of physics that is concerned with the properties of wave processes independently of their physical origin. If all the parts making up a medium were rigidly bound , then they would all vibrate as one, with no delay in the transmission of the vibration and therefore no wave motion.

On the other hand, if all the parts were independent, then there would not be any transmission of the vibration and again, no wave motion. Although the above statements are meaningless in the case of waves that do not require a medium, they reveal a characteristic that is relevant to all waves regardless of origin: Consider a traveling transverse wave which may be a pulse on a string the medium.

Consider the string to have a single spatial dimension. Consider this wave as traveling. A generalized representation of this wave can be obtained [5] as the partial differential equation.

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General solutions are based upon Duhamel's principle. Constant values of this argument correspond to constant values of F , and these constant values occur if x increases at the same rate that vt increases. That is, the wave shaped like the function F will move in the positive x -direction at velocity v and G will propagate at the same speed in the negative x -direction. In a similar fashion, this periodicity of F implies a periodicity in time as well: The amplitude of a wave may be constant in which case the wave is a c.

The outline of the variation in amplitude is called the envelope of the wave. Mathematically, the modulated wave can be written in the form: Otherwise, in cases where the group velocity varies with wavelength, the pulse shape changes in a manner often described using an envelope equation.

'A crazy experience': Kelly Slater's Surf Ranch Pro takes man-made waves on tour

There are two velocities that are associated with waves, the phase velocity and the group velocity. Phase velocity is the rate at which the phase of the wave propagates in space: Group velocity is a property of waves that have a defined envelope, measuring propagation through space i. The units of the amplitude depend on the type of wave.

Transverse mechanical waves e. These are related by:. It is related to the frequency or period by. Wavelength can be a useful concept even if the wave is not periodic in space. For example, in an ocean wave approaching shore, the incoming wave undulates with a varying local wavelength that depends in part on the depth of the sea floor compared to the wave height.

The analysis of the wave can be based upon comparison of the local wavelength with the local water depth. Although arbitrary wave shapes will propagate unchanged in lossless linear time-invariant systems , in the presence of dispersion the sine wave is the unique shape that will propagate unchanged but for phase and amplitude, making it easy to analyze.

The sinusoid is defined for all times and distances, whereas in physical situations we usually deal with waves that exist for a limited span in space and duration in time. An arbitrary wave shape can be decomposed into an infinite set of sinusoidal waves by the use of Fourier analysis. As a result, the simple case of a single sinusoidal wave can be applied to more general cases. A standing wave, also known as a stationary wave , is a wave that remains in a constant position.

This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions. The sum of two counter-propagating waves of equal amplitude and frequency creates a standing wave. Standing waves commonly arise when a boundary blocks further propagation of the wave, thus causing wave reflection, and therefore introducing a counter-propagating wave.

For example, when a violin string is displaced, transverse waves propagate out to where the string is held in place at the bridge and the nut , where the waves are reflected back. At the bridge and nut, the two opposed waves are in antiphase and cancel each other, producing a node. Halfway between two nodes there is an antinode , where the two counter-propagating waves enhance each other maximally.

There is no net propagation of energy over time. One-dimensional standing waves; the fundamental mode and the first 5 overtones. A two-dimensional standing wave on a disk ; this is the fundamental mode. A standing wave on a disk with two nodal lines crossing at the center; this is an overtone.

Waves normally move in a straight line i. Such media can be classified into one or more of the following categories:.

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