Waves Wave Terminology Wave Terminology H Height A

Wave Terminology • • H = Height A = Amplitude = 1/2 H L

Wind Waves • What influences wave size? – Wind Speed • H, L, T

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

Wave Speed (Deep Water) C = L/T = 1. 25 * √L L =

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

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

Shallow Water Waves • Deep Water Waves (Depth > L/2) C = L/T =

Shallow Water Waves • Shallow Water Waves (d < L/20) C = 3. 13

Shallow Water Waves • • • When D<L/20 Speed decreases ~ D Length decreases

$Wave Difraction$

Teahupoo – Tahiti surging breaker long wavelengths steep slope

Folly Beach - SC plunging breaker moderate slope, small wavelength

Tsunami Waves • • • Earthquakes L ~ 100 – 200 Km P ~

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

Slides: 39

Download presentation

Waves

Wave Terminology

Wave Terminology • • H = Height A = Amplitude = 1/2 H 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

Wave Motion & Energy

Wave Spectrum

Ocean surface waves

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

i. e. Effect of wind speed on H

Wave Interference

Wave Interference – Area of Fetch

Fetch Area

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

Wave Speed (Deep Water) C = L/T = 1. 25 * √L L = 1. 56 *T 2 • Slow Wave Speed – long Period (T) – Short Length (L) • Fast Wave Speed – Short Period (T) – Long Length (L)

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

Waves and Currents

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

Figure 9. 9

Orbital Motion

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

Shallow Water Waves

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

Figure 9. 12

Shallow Water Wave Height

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

$Wave Difraction$

Wave Difraction

MUNDAKA VIDEO

Teahupoo – Tahiti surging breaker long wavelengths steep slope

Teahupoo Tahiti

Pipeline - Oahu plunging breaker

Folly Beach - SC plunging breaker moderate slope, small wavelength

Rip Currents

Tsunami Waves • • • Earthquakes L ~ 100 – 200 Km P ~ 10 - 30 minutes Shallow Water Waves C over 4000 m 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.

Figure 9 p 264 (figure 1)

Figure 9. 24

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