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Ocean Waves

Capillary. Gravity. Wind generated. Tides. Tsunamis. Seiches. Ocean Waves. Capillary waves are driven by the surface tension produced by electrically polarized water molecule. Capillary waves are driven by the surface tension produced by electrically polarized water molecule.

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Ocean Waves

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  1. Capillary Gravity Wind generated Tides Tsunamis Seiches Ocean Waves

  2. Capillary waves are driven by the surface tension produced by electrically polarized water molecule Capillary waves are driven by the surface tension produced by electrically polarized water molecule

  3. San Pedro Lighthouse

  4. Waves • are alternate rises and falls, describable as simple/complex sinusoidals

  5. Crest 1 0.75 Amplitude 0.5 0.25 Height 0 0 45 90 135 180 225 270 315 360 -0.25 Wave period or Wavelength -0.5 -0.75 Amplitude -1 Trough

  6. As a wave travels through the waver, the particles travel in clockwise circles. The radius of the circles decreases as the depth into the water increases. The following animation shows a water wave traveling from left to right in a region where the depth of the water is greater than the wavelength of the waves. http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html

  7. Waves • are alternate rises and falls, describable as simple/complex sinusoidals • only add-up, always i.e., wave interference can be constructive and/or destructive

  8. 1 A B 0.5 0 0 90 180 270 360 -0.5 C -1

  9. 1 A 0.75 B 0.5 0.25 C = A+B 0 0 45 90 135 180 225 270 315 360 -0.25 -0.5 -0.75 -1

  10. 1 0.5 B A 0 0 90 180 270 360 -0.5 C -1

  11. Waves interference is always additive 4 4 3 3 2 2 1 1 0 0 -1 0 100 200 300 400 500 600 700 -1 0 100 200 300 400 500 600 700 -2 -2 -3 -3 This is the algebraic sum of these -4 -4

  12. 1 0 0 360 -1 Wave interference can be constructive or destructive

  13. 1 0 Destructive interference Destructive interference -1 Constructive interference Constructive interference Constructive interference

  14. Waves and • wave activity • Standing waves • As waves can be thought of as single or complexsinusoids,we can lookat waves ascomprisingone or moreharmonics. First Harmonic Standing Wave Pattern Second Harmonic Standing Wave Pattern Third Harmonic Standing Wave Pattern http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/waves/swf.html

  15. Waves and • wave activity • Traveling waves • Waves travel in groups,and thegroupvelocityis one-half the velocity of individual waves. http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/waves/swf.html

  16. Waves • are alternate rises and falls, describable as simple/complex sinusoidals • only add-up, always i.e., wave interference can be constructive and/or destructive • carry energy, not matter light is an exception, it travels in waves and as particles

  17. 104 Capillary waves 103 Gravity waves in deepwater, V  1.25 L 102 Wave speed or velocity (cm/s) 10 1 10-1 1 101 102 103 104 105 106 107 Wavelength (cm)

  18. Output from a shallow water equation model of water in a bathtub. The water experiences five splashes which generate surface gravity waves that propagate away from the splash locations and reflect off of the bathtub walls. http://en.wikipedia.org/wiki/Ocean_surface_wave

  19. Waves carry energy, not matter The orbital motion of representative water molecules: orbital size decreases with depth, with negligible water motion at depth  ½ wavelength Elliptical path: waves of translation Circular path: waves of oscillation

  20. Waves break on reaching the shore. Why?

  21. Waves break as the succeeding waves catch up with preceding waves

  22. Spilling breakers form when the bottom slopes gradually Spilling breakers form when the bottom slopes gradually

  23. Plunging or surging breakers form when the bottom slope is steep Plunging or surging breakers form when the bottom slope is steep

  24. Three factors affect wind wave development: (a) Wind speed, (b) Wind duration, and (c) Fetch

  25. How wind affects the wave height

  26. Conditions conducive of a fully developed sea Wave Size Wind Conditions Wind speed 19 km/hr (10 knots) 37 km/hr (20 knots) 56 km/hr (30 knots) 74 km/hr (40 knots) 92 km/hr (50 knots) Fetch 19 km 139 km 518 km 1313 km 2627 km Wind duration 2 hr 10 hr 23 hr 42 hr 69 hr Average height 0.27 m 1.5 m 4.1 m 8.5 m 14.8 m Average Length 8.5 m 33.8 m 76.5 m 136 m 212 m Average period 3.0 sec 5.7 sec 8.6 sec 11.4 sec 14.3 sec

  27. Wave energy versus wavelength for fully developed sea: Stronger winds generate waves that are both longer and more energetic, on average 75 km/hr Relative wave energy 55 km/hr 37 km/hr 20 50 100 200 500 1000 Wavelength (m)

  28. http://www.oceanweather.com/data/global.html

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