Turbulence Development in Coupled Wind-Wave Flow: Wave Age Effects and Scaling Behavior

Turbulence in wind–wave interactions plays a critical role in coastal boundary layer dynamics and structural loading during hurricanes. Analysis of these coupled wind-wave flows and their effects on structures is essential to improve coastal resilience to these extreme events. In this study, we conduct large-eddy simulations (LES) of wind introduced over waves under a range of wave age and interaction distance conditions to investigate how turbulence develops in coupled wind-wave flows. A wavelet-based decomposition technique is applied to separate the velocity field into wave-coherent and random components, enabling a scale-specific analysis of turbulence development.

Our results show that wave-coherent fluctuations form rapidly and reach a quasi-steady state within a short fetch, while random turbulence evolves more slowly and requires a longer wind–wave interaction distance to reach an equilibrium condition. We introduce dimensionless numbers to characterize the turbulence development length and reveal how wave age modulates both components—with a particularly strong influence on the wave-coherent fluctuations. These findings provide new insight into the development of wind–wave boundary layers that can support the design of coupled wind-wave experimental facilities and contribute to improved modeling of loads on coastal structures during extreme weather events.