Waves And Water Dynamics

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Waves And Water Dynamics


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disturbing force
- the energy that causes ocean waves to form- wind blowing across ocean surface- movement of fluids with different densities (waves travel along the interface between the two)
ocean waves
- along an air-water interface, the movement of air across the ocean surface creates ocean waves
internal waves
- water-water interface- movement of water of different densities- can be much larger than surface waves, but aren't as energetic- created by: tidal movement, turbidity currents, wind stress, passing ships
- a layer of rapidly changing density- associated with internal waves
seismic sea waves/tsunami
- caused by sea floor movement: - turbidity currents- volcanic eruptions- fault slippage
progressive waves
- waves that oscillate uniformly and progress or travel without breaking - longitudinal, transverse, orbital
longitudinal waves
- push-pull in the same direction that the energy is traveling- shape of the wave (waveform) moves through the medium by compressing and decompressing- energy can be transmitted through all states of matter
transverse waves
- energy travels at right angles to the direction of the vibrating particles- transmit energy only through solids
orbital waves
- interface waves- involves components of both longitudinal and transverse waves- move in circular orbits
still water level
- halfway between the crests and troughs- zero energy level- level of the water if there were no waves
wave breaks
- the wave is too steep to support itself- anytime the 1:7 ratio is exceeded (along shoreline or out at sea)- Ex:wave 7m long can only be 1m high
- the number of wave crests passing a fixed location per unit of time- inverse of the period
circular orbital motion
- as a wave travels, the water passes the energy along by moving in a circle- wave itself doesn't travel the entire distance, but the waveform does
wave base
- equal to one half the wavelength (L/2) measured from still water level- circular orbits become so small that movement is negligible
deep-water waves
- water depth (d) is greater than the wave base (L/2)- have no interference with the ocean bottom
Celerity (C)
- wave speed - wavelength (L)/period (T)- the longer the wavelength, the faster the wave travels- depends only on wavelength
shallow-water waves
- depth (d) is less than 1/20 of the wavelength (L/20)- long waves- ocean floor interferes with their orbital motion- speed is only influenced by gravitational acceleration and the water depth (gravitational acc. remains constant on Earth)- particle motion is in a very flat elliptical orbit that approaches horizontal (back and forth) oscillation
transitional waves
- intermediate waves- characteristics of shallow and deep water waves- wave speed depends partially on water depth and partially on wavelength
capillary waves
- small, rounded waves with V-shaped troughs- wavelengths less than 1.74 cms- capilarity is the dominant restoring force that works to destroy these waves, to smooth ocean surface
gravity waves
- symmetric waves- wavelength exceeding 1.74 cms- gravity is dominant restoring force- wave height increases more rapidly than wavelength; crests become pointed and troughs rounded- results in a trochoidal waveform
sea area ("sea")
- area where wind-driven waves are generated
factors that determine the amount of energy in waves
1) wind speed2) duration - length of time during which the wind blows in one direction3) the fetch - the distance over which the wind blows in one direction
fully developed sea
- equilibrium condition- waves can grow no further because they lose as much energy breaking as white-caps under the force of gravity as they receive from the wind
- uniform, symmetrical waves that have traveled out of the area where they originated- move with little loss of energy, transporting energy away from one sea area and depositing it in another
shoaling water
shallow water
physical changes as deep-water waves of a swell move toward continental margins
- wave speed decreases- decrease in wavelength- wave height increases- increase in wave steepness (H/L) until 1:7 ratio and wave breaks as surf
wave refraction
- as a wave approaches shore at a slight angle to the shore, some segment of the wave will "feel bottom" first and will slow before the rest of the wave- the bending of each wave crest as the waves approach the shore- refraction of waves along an irregular shoreline distributes wave energy unevenly along the shore
orthogonal lines
- wave rays- are drawn perpendicular to wave fronts and are spaced so energy between lines is equal at all times- help show energy is distributed along the shoreline by breaking waves- converge on headlands - heavy erosion- diverge in bays - deposition
wave diffraction
- results from wave energy being transferred around or behind barriers that impede the wave's forward motion- any point on a wave front is a source from which energy can propagate in all directions
standing waves
- produced when waves are reflected at right angles to a barrier- the sum of two waves with the same wavelength moving in opposite directions, resulting in no net movement (no circular motion)- nodes - lines along which there is no vertical movement- antinodes - crests that alternately become troughs
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