Computational modeling of coupled waves and vegetation stem dynamics in highly flexible submerged meadows

Abstract

In this study, we have developed a two-way fully coupled hydrodynamic-vegetation model that includes a spatially and temporally variable drag coefficient of flexible submerged aquatic vegetation (SAV). The developed model consists of a nonhydrostatic wave model (NHWAVE) that solves the Navier-Stokes equations and a numerical model for vegetation stem dynamics that solves the instantaneous forces applied by flow on vegetation stems. The results of the developed model are validated against a number of laboratory-scale experiments on wave attenuation, stem orientation, and stem base forces, and then applied to an idealized configuration to further investigate the effects of vegetation induced drag coefficient on waves velocity field, wave attenuation, and vegetation dynamics along a numerical flume. The model was able to reproduce experimental results without parameter tuning. By adopting the N-pendula approach, the stem dynamics model solves the instantaneous orientation of segments along each stem and uses this information to compute a spatially and temporally varying vegetative drag coefficient within the meadow. When compared with laboratory experiments, incorporating this new mechanism for flexible vegetation in the wave model resulted in improvement over results with rigid vegetation. Through highly detailed representation of vegetation, the model can reliably predict wave attenuation over marshes and seagrass meadows, evaluate potential storm damages to these features, and calculate instantaneous orientation of plant stems or shoots which has implications for their photosynthesis.