Wave-induced boundary layers underneath a flexible structure
Esra Uksul (TU Delft - Multi Phase Systems)
Angeliki Laskari (TU Delft - Multi Phase Systems)
Sebastian Schreier (TU Delft - Ship Hydromechanics and Structures)
Christian Poelma (TU Delft - Process and Energy)
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Abstract
The interaction between propagating waves and flexible floating structures remains poorly understood, particularly in terms of interface boundary layer characteristics, which play a role in influencing wave attenuation and energy dissipation. In this study, phase-locked Particle Image Velocimetry was used to capture velocity fields beneath a continuous, compliant structure subjected to regular waves of varying order and steepness. The results confirm the formation of a distinct wave-induced boundary layer at the fluid-structure interface. For second-order waves with low steepness (H/λ=0.02), an adapted form of Stokes’ second problem predicts the boundary layer thickness, velocity overshoot, and exponential decay with depth reasonably well. However, for steeper second-order or third-order waves (H/λ=0.033–0.064), the experimental data reveal significant deviations from the model - specifically in the boundary layer structure and in the slope of the velocity profile for attenuating waves. These discrepancies suggest that classical linear theory is insufficient in capturing the full complexity of wave-structure interactions as wave steepness increases and nonlinear effects become more pronounced.
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