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

26. Wave Difraction

27. MUNDAKA VIDEO

28. Teahupoo – Tahitisurging breakerlong wavelengthssteep slope

29. Teahupoo Tahiti

30. Pipeline - Oahuplunging breaker

31. Folly Beach - SCplunging breakermoderate slope, small wavelength

32. Rip Currents

33. 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.

34. Figure 9 p264 (figure 1)

35. Figure 9.24

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