Wave-Turbulence Decomposition in the Surf Zone

Breaking waves within the surf zone intermittently inject momentum into the water column, resulting in superposition of coherent wave-induced motions and breaking wave-generated turbulence. Wave-induced motions and turbulence often overlap in both spatial and temporal scales, making it difficult to distinguish their individual contributions. Accurate separation of wave and turbulence signals is critical for understanding near-bed sediment transport and estimating turbulence characteristics. We performed laboratory experiments in a large-scale outdoor wave flume with a sediment beach profile. Velocity and pressure data were collected at two surf-zone stations using Nortek Vectors positioned 10 cm above the bed, sampling at 64 Hz. In this study, we propose a modified coherence-based filtering approach, building on the approach of Benilov and Filyushkin (1970). By calculating the frequency-domain coherence between pressure and velocity signals, we adaptively identify cutoff frequencies for each velocity component and isolate turbulence motions. The turbulence signal is then reconstructed in the time domain, allowing direct estimation of turbulence statistics from single-point measurements. We evaluate the method performance in decomposing the signals and estimating key turbulence parameters, demonstrating its practical application in wave-dominated environments.