Waves. Wave Terminology H = Height A = Amplitude = 1/2H L = λ = Wave Length ( distance 2...
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Transcript of Waves. Wave Terminology H = Height A = Amplitude = 1/2H L = λ = Wave Length ( distance 2...
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
Wind Waves• What influences wave size?
– Wind Speed• H, L, T
– Duration of wind• Maximum H
– Fetch • Maximum H
– Wave Height (H)– Wave Interference
Wave Speed (Deep Water)
C = L/T = 1.25 * √LL = 1.56 *T2
• Slow Wave Speed – long Period (T)– Short Length (L)
• Fast Wave Speed– Short Period (T)– Long Length (L)
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 (d < L/20)C = 3.13 * √DC = L / T
– C (speed) diminishes in shallow water– T (period) remains constant– .. So L (Length) must also diminish– C & L depend on depth
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
Teahupoo – Tahitisurging breakerlong wavelengthssteep slope
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.