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Waves - Coggle Diagram
Waves
Waves vs Swell
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In the context of comparing waves and swell, these waves are usually called wind waves
Wind waves are waves that are currently being formed by the wind around them. They are often much smaller than swell, and can disappear quickly if winds die down.
Without wind, all waves slowly die out
Wind waves can often appear on top of swell, especially when current wind direction does not align with the swell direction
Measuring waves
Waves are measured by height, period, and direction
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Period is the time it takes from crest to crest to pass a point. It is actually a measure of the size of waves and not the speed like it might sound. This is the most reliable way to measure a wave's energy.
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Period is the same thing as wavelength, just measured in different ways. Period is the time between crests, and wavelength is the distance between crests
Causes of waves
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Wind Duration
The longer the wind is able to act on waves, the larger they will become.
Fetch
Fetch is relevant even out to 1,000 miles
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This is the reason that you will never see waves beyond a certain size on lakes, no matter what. Because the wind does not have the very long distance to blow over, waves can never build up to massive strength.
As any of these three factors increase, the size of wave will increase. This process is essentially the wind transferring its energy into the water. The more energy it has to give and the more time it has to give, the larger the waves will be.
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Waves breaking
Types of Break
Dump
Dump or plunging waves happen when a wave impacts a sudden depth change, they are more common in offshore wind conditions.
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Often this wave will trap air under the break, this is what causes the loud crashing sound of waves.
Reflect
When waves impact smooth, vertical, man made surfaces they bounce off rather than losing their energy
Outgoing waves are produced and they impact with incoming waves. At the point of impact the height of the wave is doubled
This is also called clapotis, and rarely extends more than 30 yards
Refract
Waves that pass through a narrow passage will be refracted or diffracted into a curve centered on the passage. This new wave will have less energy with a reduced height and speed along with greater wavelength.
Spill
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The wave breaks over a longer period of time, slowly losing its energy as water spills from the crest
Why do waves break?
As waves get closer to shore, the bottom of the wave meets the ocean floor.
Friction between the wave and the ocean floor slows down the waves, reducing wavelength, and increasing wave height.
As the base of the wave slows, the surface does not, this increases the "steepness" of the wave or the ratio between the wave height and wavelength.
When the ratio becomes greater than 1:7, the wave becomes unstable and breaks, forming a crest.
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