Waves - Characteristics, Types, and Energy

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Waves - Characteristics, Types, and Energy

  1. 1. Waves and Water Dynamics© 2011 Pearson Education, Inc.
  2. 2. Chapter Overview Most waves are wind-driven. Most waves are generated by storms. Waves transmit energy across the ocean surface. Tsunami are special fast, long waves generated by seismic events. © 2011 Pearson Education, Inc.
  3. 3. Wave Generation Disturbing force causes waves to form Wind blowing across ocean surface Interface of fluids with different densities  Air – ocean interface  Ocean waves  Air – air interface  Atmospheric waves  Water – water interface  Internal waves © 2011 Pearson Education, Inc.
  4. 4. Internal Waves Associated with pycnocline Larger than surface waves Caused by tides, turbidity currents, winds, ships Possible hazard for submarines © 2011 Pearson Education, Inc.
  5. 5. Other Types of Waves Splash wave  Coastal landslides, calving icebergs Seismic sea wave or tsunami  Sea floor movement Tides  Gravitational attraction among Moon, Sun, and Earth Wake  Ships © 2011 Pearson Education, Inc.
  6. 6. Speed of Deep Water Waves © 2011 Pearson Education, Inc.
  7. 7. Energy in Ocean Waves © 2011 Pearson Education, Inc.
  8. 8. Wave Movement Waves transmit energy Cyclic motion of particles in ocean  Particles may move  Up and down  Back and forth  Around and around Particles in ocean waves move in orbital paths © 2011 Pearson Education, Inc.
  9. 9. Progressive Waves  Progressive waves oscillate uniformly and progress without breaking  Longitudinal  Transverse  Orbital © 2011 Pearson Education, Inc.
  10. 10. Orbital Waves (3 types)  Waves on ocean surface  Anatomy  Crest  Trough  Wave height (H)  Wavelength (L) © 2011 Pearson Education, Inc.
  11. 11. Orbital Wave CharacteristicsWave steepness = Height/Length  If wave steepness > 1/7, wave breaks. EX:: A wave 7 meters long can only be 1 meter high without breaking. If the wave is any higher than that, it will break. © 2011 Pearson Education, Inc.
  12. 12. Garrett McNamara Breaks Big Wave World Record: 100 ft wave. Portugal.
  13. 13. Wave period (T) = time for one wavelength topass fixed point (The time it takes for two wavecrests to pass a given point.)Wave frequency = inverse of period or 1/T Note: Frequency is the reciprocal of the time taken to complete one cycle (the period), or 1/T.EX 2: Waves with a period of 12 seconds will have a frequency of 1/12 or0.083, which converts to 5 periods/minute.
  14. 14. Orbital Wave Characteristics  Diameter of orbital motion decreases with depth of water  Wave base = ½ L  Hardly any motion below wave base due to wave activity  Ex: A wave that has a wavelength with 10 meters will have negligible movement at 5 meters below the still water level. © 2011 Pearson Education, Inc.
  15. 15. Circular Orbital Motion  Wave particles move in a circle Wave Motion © 2011 Pearson Education, Inc.
  16. 16. 1. Deep-Water Waves  Water depth is greater than wave base (>½L) -depth is greater than ½ wavelength  Wave speed = celerity (C)  C = L (Wavelength)/T (Period) © 2011 Pearson Education, Inc.
  17. 17. 2. Transitional Waves  Characteristics of both deep- and shallow-water waves  Celerity depends on both water depth and wavelength - Wavelength is 2 to 20 that water depth. © 2011 Pearson Education, Inc.
  18. 18. 3. Shallow-Water Waves  Water depth is < ½ L  C (meters/sec) = 3.13 √ d(meters) or  C (feet/sec) = 5.67 √d (feet)  Where d is water depth -tsunamis and tides are types of waves are examples of shallow water waves. © 2011 Pearson Education, Inc.
  19. 19. Write out:Wave Type Deep vs. Shallow Affects the ocean bottom?Wind Wave Deep Does not affect bottom (depth > ½ wavelength)Tsunami Shallow Strongly affects bottom. (depth is < ½ of wavelength).Tides Shallow Affects bottom.

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