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Ocean Waves Capillary Gravity Wind generated Tides Tsunamis Seiches.

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Presentation on theme: "Ocean Waves Capillary Gravity Wind generated Tides Tsunamis Seiches."— Presentation transcript:

1 Ocean Waves Capillary Gravity Wind generated Tides Tsunamis Seiches

2 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 are alternate rises and falls, describable as simple/complex sinusoidals

5 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 04590135180225270315360 Crest Amplitude Height Trough Wave period or Wavelength

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

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

9 -0.5 0 0.5 1 090180270360 A B

10 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 04590135180225270315360 A B C = A+B

11 -0.5 0 0.5 1 090180270360 A B C

12 -4 -3 -2 0 1 2 3 4 0100200300400500600700 Waves interference is always additive This is the algebraic sum of these

13 Wave interference can be constructive or destructive

14 Constructive interference Destructive interference

15 Second Harmonic Standing Wave Pattern First Harmonic Standing Wave Pattern Third Harmonic Standing Wave Pattern http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/waves/swf.html Waves and wave activity Standing waves As waves can be thought of as single or complex sinusoids, we can look at waves as comprising one or more harmonics.

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

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

18 10 -1 110 1 10 2 10 5 10 4 10 3 10 6 10 7 10 4 10 3 10 2 10 1 Wavelength (cm) Wave speed or velocity (cm/s) Capillary waves Gravity waves in deepwater, V  1.25  L

19 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.shallow water equation http://en.wikipedia.org/wiki/Ocean_surface_wave

20 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 Circular path: waves of oscillation Elliptical path: waves of translation

21 Waves break on reaching the shore. Why?

22 Waves break as the succeeding waves catch up with preceding waves

23 Spilling breakers form when the bottom slopes gradually

24 Plunging or surging breakers form when the bottom slope is steep

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

26 How wind affects the wave height

27 Windspeed 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 Windduration 2 hr 10 hr 23 hr 42 hr 69 hr Wind Conditions Averageheight 0.27 m 1.5 m 4.1 m 8.5 m 14.8 m AverageLength 8.5 m 33.8 m 76.5 m 136 m 212 m Averageperiod 3.0 sec 5.7 sec 8.6 sec 11.4 sec 14.3 sec Wave Size Conditions conducive of a fully developed sea

28 20501002005001000 Relative wave energy Wavelength (m) 75 km/hr 55 km/hr 37 km/hr Wave energy versus wavelength for fully developed sea: Stronger winds generate waves that are both longer and more energetic, on average

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


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