Interactions Between Internal Solitary Waves and Floating Canopies

TL;DR

This study investigates how internal solitary waves interact with floating canopies of different porosities and lengths using laboratory experiments and simulations, revealing complex nonlinear behaviors and energy transfer mechanisms.

Contribution

It introduces a combined experimental and simulation approach to analyze internal wave-canopy interactions, highlighting the effects of canopy porosity and length on wave dynamics.

Findings

Higher-porosity canopies cause minor amplitude reduction and negligible energy loss.

Dense canopies induce strong shear layers and complex nonlinear wave modulation.

Extended canopies lead to quasi-steady wave states with significant phase speed reduction.

Abstract

Interactions between internal solitary waves and floating canopies of varying length and porosity are examined via laboratory experiments and complementary simulations for a miscible, two-layer system. In both approaches, internal solitary waves of varying amplitudes are generated by a jet-array mechanism that is driven by the nonlinear eKdV solution. Pycnocline displacements, phase speeds, and velocity fields are obtained using synchronized planar laser-induced fluorescence and particle imaging velocimetry systems in the experiment. In the simulations, the canopy is represented as a porous zone with prescribed porosity and hydraulic conductivity determined by the Kozeny-Carman model, which is validated by comparing simulated and measured horizontal velocity profiles. The higher-porosity (transitional) canopy produces a nearly monotonic, albeit minor, amplitude reduction and negligible wave energy dissipation after the interaction. However, the shear layer developed at the bottom edge of the lower-porosity (dense) canopy grows to a comparable strength as the shear sustained by the internal solitary wave profile at the pycnocline. The vortex pair generated by this shear accelerates the upper-layer fluid beneath the canopy, leading to complex nonlinear amplitude modulation and significant wave transformation. With an extended canopy length, the internal solitary waves settle to a quasi-steady state with a significant phase speed reduction. Upon the wave exiting the canopy, flow separation at the downstream edge of the canopy again pairs with the shear at the pycnocline, inducing an intensified jet. This complex interaction leads to energy transfer between kinetic and potential energy under the dense canopy.