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The first prelim will be held during regular class time on Thursday 21 February A short in-class review will be held Tuesday 19 February to go over student submitted questions Submit review questions to Yianna Samuel by Friday 15 February Important Announcement

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Why Study Waves?

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Wave Prediction and Shipping

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Wave Prediction and Construction of Coastal Structures

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Wave Prediction and Construction of Off-Shore Structures

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Wave-Induced Beach Erosion and Sediment Transport

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Wave Prediction and Recreation

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Fundamental Principles

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Wave Parameters Wave Period = Time it Takes a Wave Crest to Travel one Wavelength (units of time) Wave Frequency = Number of Crests Passing A Fixed Location per Unit Time (units of 1/time) Wave Speed = Distance a Wave Crest Travels per Unit Time (units of distance/time) Wave Steepness = Wave Height/Wavelength

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Constructive, Destructive and Mixed Addition of Two Waves Constructive Destructive Mixed

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Ideal Deep-Water Waves Propagate Energy not Mass

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Two Critical Points to Note About Wave Speeds Deep-Water Waves (Bottom Depth > L/2) –Speed is a Function of Wavelength Only –Waves with Longer Wavelength move faster than Waves with Shorter Wavelength Shallow-Water Waves (Bottom Depth < L/20) –Speed is a Function of Depth Only –Waves Travel Slower in Shallower Water Irrespective of Wavelength as long as Depth < L/20 _________________ Note that there is also an intermediate region (L/20 < Depth < L/2) where Wave Speed is a Function of Both Wavelength & Depth Note: L = wavelength

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Speed of Deep-Water and Shallow- Water Waves as a Function of Wavelength and Depth

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Deep-Water and Shallow-Water Wave Regions

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The Size of Wind Generated Waves is a Function of: 1.Wind Speed 2.Duration of Wind 3.Fetch - the distance over which wind can blow without obstruction

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The Importance of Fetch

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Full Developed Waves (Unlimited by Fetch and Duration)

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Lateral Spreading of Wave Energy from a Storm Source (95% of Energy Contained Within ±45 o of Storm Direction)

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Wave Measurement Methods

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Wave Height Measured with Bottom-Moored Pressure Sensor

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Significant Wave Heights Derived from the Shape of the Returned Beam on the Topex-Poseidon Altimeter

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The Distribution of Wave Energy as a Function of Wave Period or Wavelength…

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Distribution of Wave Energy in the Ocean as a Function of Wave Frequency or Wavelength

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Some Interesting Things About Waves…

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Wave Dispersion: Self Sorting of Deep-Water Waves Leaving a Storm Region based on Wavelength. It Occurs Because Longer Wavelength Waves Travel Faster than Shorter Wavelength Waves (for Deep Water).

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Bending of Shallow-Water Wave Fronts Due to Change in Bottom Depth. The Leading Edge of a Wave Front Enters Shallower Water and Slows While the Remaining Front Continues at Higher Speed. The Net Result is a Rotation of Wave Fronts To Become Parallel with Bottom Depth Contours. Wave Refraction:

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Consequence of Wave Refraction Focusing and Defocusing of Wave Energy on Headlands and Bays, Respectively

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Wave Diffraction

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Along Shore Sediment Transport

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Along-Shore Sediment Transport Obstructed by Groins

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Initiation and Propagation of a Tsunami

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Motion of Seiche Caused by a Storm Over a Semi-Enclosed Body of Water

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Internal Waves Travel along Density Discontinuities in the Ocean Interior

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Thin Layers of Phytoplankton Oscillating with an Internal Wave Formed along the Continental Shelf

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Kelvin and Rossby Waves - Planetary Waves -

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Rossby Waves in the Equatorial Pacific

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1.Waves Propagate Energy and not Mass 2.Waves Add Constructively or Destructively 3.Deep-Water Wave Speed is a Function of Wavelength 4.Shallow-Water Wave Speed is a Function of Bottom Depth 5.Wave Dispersion: Sorting of Deep-Water Waves Based on Wavelength 6.Wave Refraction: Bending of Shallow-Water Waves Based on Depth 7.Wave Height Determined by: Wind Speed, Wind Duration and Fetch Summary Points

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8.Waves Hitting a Shore Obliquely Will Cause along Shore Transport of Sediment 9.Constructed Structures such a Groins will Block the Along Shore Sediment Transport 10.Tsunami are Generated by Underwater Earthquakes or Landslides and Propagate across Whole Ocean Basins 11.Seiches are Standing Waves formed in Semi- Enclosed Bodies of Water 12.Internal Waves Propagate along Density Discontinuities (Pycnoclines) in the Ocean Interior 13.Kelvin and Rossby Waves are Important Planetary Wave

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