2.0 Aeration in Wave Loading
Aeration appears to play an important role within the impact process when the wave loading is applied on the structure. Aeration is defined as the process by which air is circulated through, mixed with or dissolved in a liquid or substance. In this case, aeration refers to the mixture of sea water with air bubbles. The existence of the air content within the water has an effect on the temporal variations of pressure caused by waves breaking on structures (Biackmore & Hewson, 1984; Griffiths, 1994).
2.1 Causes of Aeration
Aeration in ocean is mainly due to production of bubble. Bubble can be produced via the following processes:
• Biological production - This occurs where there are large aggregations of phytoplankton such as in coastal regions.
• Entrapment of air by capillary waves - These waves have a very short wavelength and are produced by wind and surface tension at the air-sea boundary.
• White capping - This occurs when air is entrapped during the process of deep water spilling breaking of ocean surface waves (Le Blond and Mysak, 1978).
• Wave breaking - This is caused by the steepening of gravity waves beyond a critical limit
(Galvin 1968) as a result the wave overturns or breaks resulting in the entrapment of air which produces an abundance of bubbles.
Wave breaking is by far the most significant of the processes producing bubbles at a coastal structure. When a wave breaks in sea water a large number of bubbles are produced and these bubbles generally persist for many wave periods. The bubbles produced also do not tend to coalesce and hence remain small, rising slowly through the water (Scott, 1975). There is also a tendency for the bubbles to remain at the surface for some duration...
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...upon wave impact pressures it is not essential that the exact quantity and size of the bubbles are known, however the volume fraction of air in the water is considered important (henceforth referred to as 'void fraction').
The void fraction can be found by measuring the resistance of a volume of the fluid between two probes, as the resistance between the two probes increases as the air content increases. In order to adequately measure the movement of air pockets and air bubbles a vertical array of co-located pressure and aeration transducers was required. To measure wave impact void fractions in the field the aeration transducers must withstand storm conditions, operate over a range of temperature and salinity variations, and be appropriately attached to the coastal structure. Hence the development of field wave impact aeration gauges was a substantial problem.
An increase in pebble roundness in the direction of long shore drift. The process of attrition will erode the pebbles. c) A decrease of pebble size in the direction of long shore drift, again attrition is involved. d) Undercutting (active erosion of the cliffs at one end of the bay).
walking across them. The lines and pulleys and some parts of the waves are example of
Pacific Coast Of Hokkaido." Coastal Engineering Journal 54.1 (2012): 1250002-1-1250002-17. Academic Search Premier. Web. 1 Apr. 2014.
3b.The waves are very high because they have nothing close to them to make the waves slow down.
Tampa Bay Water is a seawater desalination plant located in Tampa, Florida. Their method of desalination of ocean water or brackish groundwater is another method to obtaining water from fresh surfaces or groundwater sources. This could be used to replace the need for a water supply dam. There are several different technologies that exist to remove salt and other impurities from ocean water. The two most commonly used methods are thermal distillation and desalination. Thermal distillation copies the natural water cycle by using heat to create a vapor that is converted into freshwater. Desalination is a process that removes some amount of salt and other minerals from saline water. The traditional process used is vacuum distillation, which boils water at less than atmospheric pressure making the water sit at a much lower temperature than normal. This is due to the fact that the boiling of liquid occurs when the vapor pressure equals the outside pressure and vapor pressure increases with temperature. Due to the reduced temperature, low-temperature "waste" heat from electrical power generation or industrial processes can be used. The processes use membranes to desalinate, by applying standard reverse osmosis technology. These membrane processes use semi-permeable membranes and pressure to separate salts from water.
The Sun’s radiation heats the upper atmosphere, sending the energy toward the earth’s surface and finally mixes with the planet’s counter-rotational currents, creating jetstream flows. The winds flow over the ocean’s surface creating friction that spawns chops, pushing up the seas forming perfect bands of open ocean swell. Pushed on by gravitational forces, the swells speed away from the winds that they came from, moving across the deeps until they feel the drag of the shallows near the coast. As the swells rise up out of themselves, they peak, curling into the liquid dreams that we surfers ride (Kampton 4).
Surfers gave this part of the day this name because the water has a clean and glassy
moving back and forth in the same direction as the waves are traveling, as secondary or transverse shear waves, known as S
Thunderheads. The air begins swirling around the storm center, for the same reason that the air swirls around a tornado center. As this air swirls in over the sea surface, it soaks up more and more water vapor. At the storm center, this new supply of water vapor gets pulled into the thunderhead updrafts, releasing still more energy as the water vapor condenses. This makes the updrafts rise faster, pulling in even larger amounts of air and
The rate of evaporation can increase if the gas pressure decreases around the liquid. Heat energy is used to break the bonds that hold water molecules together, that is why water easily evaporates at the boiling point but evaporates much slower at the freezing point. Net evaporation happens when the rate of evaporation surpasses the amount of condensation. Saturation occurs when these two process rates are equivalent when the humidity of the air is at one-hundred percent. On average, a fraction of the atoms in a glass of water has enough heat energy to escape from the liquid. Evaporation from the ocean is the primary device for supporting the surface-to-atmosphere part of the water cycle. Evaporation is the pathway where water moves from the liquid state back into the water cycle as atmospheric vapor. Studies have shown that the major bodies of water are nearly ninety percent of the moisture in the atmosphere from the evaporation of the water, the ten percent left is contributed from plant transpiration. Evaporation can only occur when water is available. It also requires the humidity of the surrounding atmosphere to be less than the evaporating surface. At one-hundred percent relative humidity, there is no more evaporation. The wind chill effect is one of the
Scientists aren't exactly sure of how or why algal blooms get started. One theory is that when temperature, salinity, and nutrients reach certain levels there is a massive increase in the amount of algae.
...smits the waves from one direction but as soon as it reflects it blocks them from the other. [1]