In fluid dynamics, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Wind waves range in size from small ripples to huge rogue waves. When directly being generated and affected by the local winds, a wind wave system is called a wind sea. After the wind ceases to blow, wind waves are called swell. They have been generated elsewhere, or some time ago. Wind waves in the ocean are called ocean surface waves.
Tsunamis are a specific type of wave not caused by wind but by geological effects. In deep water, tsunamis are not visible because they are small in height and very long in wavelength. They may grow to devastating proportions at the coast due to reduced water depth.
Wave Formation
Five factors influence the formation of wind waves, 1. Wind speed, 2 Distance of open water that the wind has blown over, 3 Width of area affected by fetch, 4 Time duration the wind has blown over a given area, 5 Water depth.
All of these factors work together to determine the size of wind waves. The greater each of the variables, the larger the waves. Waves are characterized by:
• Wave height (from trough to crest)
• Wavelength (from crest to crest)
• Wave period (time interval between arrival of consecutive crests at a stationary point)
• Wave propagation direction
Types of Wind Waves
Three different types of wind waves develop over time:
1. Capillary waves, or ripples
2. Seas
3. Swells
Ripples appear on smooth water when the wind blows, but will die quickly if the wind stops. The restoring force that allows them to propagate is surface tension. Seas are the larger-scale, often irregular motions that form under sustained winds. They tend to last much longer, even after the wind has died, and the restoring force that allows them to persist is gravity. As seas propagate away from their area of origin, they naturally separate according to their direction and wavelength. The regular wave motions formed in this way are known as swells.
Individual "rogue waves" much higher than the other waves in the sea state can occur. Such waves are distinct from tides, caused by the Moon and Sun's gravitational pull.
Wave Breaking
A breaking wave is one whose base can no longer support its top, causing it to collapse. A wave breaks when it runs into shallow water, or when two wave systems oppose and combine forces. When the slope, or steepness ratio, of a wave is too great, breaking is inevitable.
Three main types of breaking waves are mainly identified by surfers or surf lifesavers. Their varying characteristics make them more or less suitable for surfing, and present different dangers.
- Spilling, or rolling: These are the safest waves on which to surf. They can be found in most areas with relatively flat shorelines. They are the most common type of shorebreak.
- Plunging, or dumping: these break suddenly and can "dump". Strong offshore winds and long wave periods can cause dumpers. They are often found where there is a sudden rise in the sea floor, such as a reef or sandbar.
- Surging: these may never actually break as they approach the water's edge, as the water below them is very deep. They tend to form on steep shorelines.
Tsunamis are a specific type of wave not caused by wind but by geological effects. In deep water, tsunamis are not visible because they are small in height and very long in wavelength. They may grow to devastating proportions at the coast due to reduced water depth.
Wave Formation
Five factors influence the formation of wind waves, 1. Wind speed, 2 Distance of open water that the wind has blown over, 3 Width of area affected by fetch, 4 Time duration the wind has blown over a given area, 5 Water depth.
All of these factors work together to determine the size of wind waves. The greater each of the variables, the larger the waves. Waves are characterized by:
• Wave height (from trough to crest)
• Wavelength (from crest to crest)
• Wave period (time interval between arrival of consecutive crests at a stationary point)
• Wave propagation direction
Types of Wind Waves
Three different types of wind waves develop over time:
1. Capillary waves, or ripples
2. Seas
3. Swells
Ripples appear on smooth water when the wind blows, but will die quickly if the wind stops. The restoring force that allows them to propagate is surface tension. Seas are the larger-scale, often irregular motions that form under sustained winds. They tend to last much longer, even after the wind has died, and the restoring force that allows them to persist is gravity. As seas propagate away from their area of origin, they naturally separate according to their direction and wavelength. The regular wave motions formed in this way are known as swells.
Individual "rogue waves" much higher than the other waves in the sea state can occur. Such waves are distinct from tides, caused by the Moon and Sun's gravitational pull.
Wave Breaking
A breaking wave is one whose base can no longer support its top, causing it to collapse. A wave breaks when it runs into shallow water, or when two wave systems oppose and combine forces. When the slope, or steepness ratio, of a wave is too great, breaking is inevitable.
Three main types of breaking waves are mainly identified by surfers or surf lifesavers. Their varying characteristics make them more or less suitable for surfing, and present different dangers.
- Spilling, or rolling: These are the safest waves on which to surf. They can be found in most areas with relatively flat shorelines. They are the most common type of shorebreak.
- Plunging, or dumping: these break suddenly and can "dump". Strong offshore winds and long wave periods can cause dumpers. They are often found where there is a sudden rise in the sea floor, such as a reef or sandbar.
- Surging: these may never actually break as they approach the water's edge, as the water below them is very deep. They tend to form on steep shorelines.
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