Ocean Waves Capillary Gravity Wind generated Tides Tsunamis Seiches
produced by electrically polarized water molecule Capillary waves are driven by the surface tension produced by electrically polarized water molecule
San Pedro Lighthouse
Waves are alternate rises and falls, describable as simple/complex sinusoidals are alternate rises and falls, describable as simple/complex sinusoidals
Crest Amplitude Height Trough Wave period or Wavelength
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.
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
A B
A B C = A+B
A B C
Waves interference is always additive This is the algebraic sum of these
Wave interference can be constructive or destructive
Constructive interference Destructive interference
Second Harmonic Standing Wave Pattern First Harmonic Standing Wave Pattern Third Harmonic Standing Wave Pattern 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.
Waves and wave activity Traveling waves Waves travel in groups, and the group velocity is one- half the velocity of individual waves.
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
Wavelength (cm) Wave speed or velocity (cm/s) Capillary waves Gravity waves in deepwater, V 1.25 L
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
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
Waves break on reaching the shore. Why?
Waves break as the succeeding waves catch up with preceding waves
Spilling breakers form when the bottom slopes gradually
Plunging or surging breakers form when the bottom slope is steep
Three factors affect wind wave development: (a) Wind speed, (b) Wind duration, and (c) Fetch
How wind affects the wave height
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
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