Laboratory studies on the effect of tidal current on wave propagation and nonlinear characteristics of reef coasts
The wave transformation and the nonlinear characteristics along the coral reef coasts with the effect of tidal current were determined through laboratory experiments.The cross-reef variations of wa-ter surface time series,wave height,mean water level,wave nonlinear parameters and higher harmonic waves with both shoreward and seaward currents with and without the effect of tidal current are ana-lyzed.Results showed that the presence of shoreward current causes a forward shift of wave phase on the reef flat while the seaward current leads to a phase lag.With the influence of the shoreward(sea-ward)current,the wave breaking point moved shoreward(seaward).The transmitted wave height on the reef flat with the shoreward current was larger than that with the seaward current while the mean water level was lower than that with the seaward current.The wave skewness amplitude and wave a-symmetry amplitude on the reef flat increased and decreased with the shoreward(seaward)current,re-spectively,in comparison with the those without the current.The Ursell number increased as the flow direction varies from the seaward side to the shoreward side.Near the reef edge,the seaward current promoted the generation of the high harmonics while the shoreward current reduced the high harmon-ics.The attenuation of the higher harmonics on the reef flat was the largest in the presence of seaward current,and was the smallest when the shoreward current exists.
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