Ocean surface wave? |
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Waves
Ocean surface waves are surface waves which occur at the surface of an ocean. That is, a wave that is guided along the interface between water and air. As the wind blows, pressure and friction forces associated with the wind perturb the equilibrium of the ocean surface. The wind actually transfers some of its energy into the water. The water is able to gain energy from the wind because of the friction between the wind and the water. This causes the surface particles to move in an elliptical motion, which is a combination of longitudinal (back and forth) and transverse (up and down) wave motions.
When an object bobs up and down on a ripple, it experiences an elliptical trajectory because ripples are not simple transverse sinusoidal waves.As the depth into the ocean increases, the radius of the elliptical motion decreases. At a depth equal to half the wavelength λ, the orbital movement is zero. The speed of the surface wave can be found using
where
- s = speed in m/s;
- λ = wavelength in m;
- d = water depth in m;
- g = gee in m/s2.
In deep water, where 
, s approximates 
. As the water depth d decreases towards the coast, this will have an effect on the speed of the crest and the trough of the wave; the crest moves faster than the trough. This causes surf, a breaking of the waves.
Individual "freak waves" (also "rogue waves", "monster waves" and "king waves") sometimes occur in the ocean, often as high as 30 metres. Such waves are distinct from tides, caused by the moon and sun's pull, and tsunamis that are caused by underwater earthquakes or landslides.
The movement of ocean waves can be captured by wave energy devices. The energy contained in 1 m2 of sea depends on the water density γ and the wave height h (= 2·amplitude (y):
Types of waves
A sequence of a wave breaking against a rocky coastlineWhen waves "break", they have different characteristics depending on factors including the structure of the ocean floor. There are three main types that are identified by surfers or surf lifesavers: plunging waves (also known as "dumpers"), spilling waves and surging waves. Their varying characteristics make them more or less suitable for surfing and present different dangers.
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