Wave Generation Frequently observed, but the physics and specific mechanisms are still poorly understood. The longer and harder the wind blows, the larger and longer period the waves generated (up to a point). Miles-Phillips, 2 stage Mechanism (1950’s): 1. Turbulence-induced pressure fluctuations over surface 2. Flow separation of air over sinusoidal surface. (see pp. 151-153 of Komar)

Wave Prediction: S-M-B method Sverdrup, Munk, and Bretschneider Relates Hs,Ts as f(U,D,F) Used wind stress, depth-limited wave growth, to develop nomograms (still used today).

Wave Prediction Nomogram

Wave Prediction: Spectral Methods Produce wave energy spectrum from given wind speed, duration, and fetch. Energy first fills the high frequency bins to the “equilibrium range”, then spills into the longer period portion of the spectrum, which has increasingly greater accommodation for energy in the equilibrium range. Progressive shift in peak period.

JONSWAP spectrum JOint North Sea Wave Project Data compiled for offshore wind intervals in the late 1960’s. Wave spectrum develops downwind. Energy-saturated equilibrium spectrum. Period and energy increase with fetch and wind speed, as expected.