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Waves

Explore wave terminology, measurements such as amplitude and period, factors influencing wave size, wave speed, and types of ocean waves. Learn about wave interference, dispersion, and the effects of shallow water on wave behavior. Discover dangerous wave types like tsunamis and how to interpret wave trains.

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Waves

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  1. Waves

  2. Wave Terminology

  3. Wave Terminology • H = Height • A = Amplitude = 1/2H • L = λ = Wave Length (distance 2 consecutive crests) • T = Wave Period (Time between 2 consecutive crests) • f = Wave Frequency = 1/T (# waves/sec) • C = Wave Speed or Celerity = L/T (m/s) • H/L = Wave Steepnes • Waves Break = H/L = 1/7

  4. Wave Motion & Energy

  5. Wave Spectrum

  6. Ocean surface waves

  7. Wind Waves • What influences wave size? • Wind Speed • H, L, T • Duration of wind • Maximum H • Fetch • Maximum H • Wave Height (H) • Wave Interference

  8. i.e. Effect of wind speed on H

  9. Wave Interference

  10. Wave Interference – Area of Fetch

  11. Fetch Area

  12. Wave formation in storms Fetch Area: Chaotic (Rogue Waves)

  13. Wave Speed (Deep Water) C = L/T = 1.25 * √L L = 1.56 *T2 • Slow Wave Speed • long Period (T) • Short Length (L) • Fast Wave Speed • Short Period (T) • Long Length (L)

  14. Wave Dispersion Outside Fetch Area: L, T & C remain constant

  15. Waves and Currents

  16. Reduction speed = Increase steepness C=L/T Steepness = H/L

  17. Figure 9.9

  18. Orbital Motion

  19. Shallow Water Waves • Deep Water Waves (Depth > L/2) C = L/T = 1.25 * √L • Intermediate Waves (L/2 > D > L/20) C ~ D, L • Shallow Water Waves (d < L/20) C = 3.13 * √D

  20. Shallow Water Waves

  21. Shallow Water Waves • Shallow Water Waves (d < L/20) C = 3.13 * √D C = L / T • C (speed) diminishes in shallow water • T (period) remains constant • .. So L (Length) must also diminish • C & L depend on depth

  22. Figure 9.12

  23. Shallow Water Wave Height

  24. Shallow Water Waves • When D<L/20 • Speed decreases ~ D • Length decreases ~ D • Height increases ~ D • Wave steepness (H/L) • Increases very quickly • H/L = 1/7 Waves break

  25. Wave Difraction

  26. MUNDAKA VIDEO

  27. Teahupoo – Tahitisurging breakerlong wavelengthssteep slope

  28. Teahupoo Tahiti

  29. Pipeline - Oahuplunging breaker

  30. Folly Beach - SCplunging breakermoderate slope, small wavelength

  31. Rip Currents

  32. Tsunami Waves • Earthquakes • L ~ 100 – 200 Km • P ~ 10 - 30 minutes • Shallow Water Waves • C over 4000m depth = 200 m/s = 720 km/h • Refracted by topography • Height at sea = 1-2 meters • Dangerous in shallow water • H~10’s m ; T~10-30 min.

  33. Figure 9 p264 (figure 1)

  34. Figure 9.24

  35. Wave trains or ‘sets’ Train Speed = ½ wave speed = 1/C

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