Wave.Length, Wave Velocity and Shoaling Characteristics of Random Waves

Fundamental properties of random waves determined by the zero-upcross method are discussed. Firstly, the wave length and the wave velocity are treated. Experiments are carried out with some supplemental definitions such as the spatial zero-up-cross method in a laboratory wave tank. Average values of K (= a ratio of measured wave length to theoretical one L_e/L_th) and R (= a ratio of measured wave velocity to theoretical one C_e/C_th) are very close to unity though data are considerably scattered. But the relations between L_e~T_e and C_e~T_e are slightly different from the theoretical ones where T_e is the measured wave period. Secondaly, breaking characteristics on sloping beaches are treated. The wave height H_b, the wave length L_b and the water depth h_b are measured at a breaking point. Breaking characteristics of random waves are considerably different from those of periodic waves. The measured wave height-water depth ratio H_b/h_b is plotted against the water depth-wave length ratio h_b/L₀ about 30~40% below the breaker inception curve for periodic waves.