Pierson-Moskowitz (PM) spectrum – for fully developed waves in deep water• JONSWAP (JOint North Sea WAve Project) spectrum – for growing wavesLecture 6
why do we need different formulas for different waves
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relative number (fraction) of crests with height𝜂𝐶 > 𝜂
this is a probalistic measure that defines how often a waves crest is over a given elevation threshold on the ocean surface
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Amplitude
maximum displacement of the wave from its mean
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The same wind will have the same wind pressure
therefore they cancel out of the calculation
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Helical Strakes
spiral fins attached to columns to supress vorext induced motion
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Stiff responses in heave, roll and pitch• Compliant responses in surge and sway
why is this the case for a TLP
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Spacing 3-10 diameters
why is this
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Offshore wind industry - future
why is this form of renewable energy growing so quickly compared to its alternatives
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survival mode
why do WECs have survival mode during extreme conditions
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interference
wave interference is when two or more wave overlap in wave and time, resulting in a new wave forming, can be constructive or destruction
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offshore wind turbine
wind energy conservation system installed in bodies of water that collects kinetic energy and turns it into electrical power
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Types based on contact point
which one is the most commonly used in practice
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Enough reserve buoyancy to maintain balance and stabilityeven with tanks flooded
why is this important during partial flooding of the tanks
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Weight shall be positioned such that the hull will not tip over
weight distribution inside a hull must be arranged so that the centre of gravity remains in a stable position relative to the centre of buoyancy and metacentre
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Deck elevation should be set above the highest Wave Crest
deck of the structure needs to be high enough to avoid wave load impacts
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energy flux
rate at which wave energy is transmitted through a units width of wave crest
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Flow (fluid particle motion) is irrotational
fluid particles do not spin about their own centres
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Fluid is incompressible
density of the fluid remains constant, volume doesn't change under pressure
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wind pressure
would opening such as doors and windows affect the drag coefficient
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1.226 kg/m3
is this value accurate for offshore envirnments or does this need to be changed
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