Modelling vegetation as complex structures in fluid–filament interaction using the elastically-articulated body method

Fluid–structure interactions in the built and natural environment commonly involve complex, heterogeneous structures. For example, terrestrial and aquatic vegetation species are morphologically complex, which is a factor not fully captured in many models used to understand important aspects of flow-vegetation dynamics. In this study, we develop and validate a multi-body method for modelling fluid interaction with slender structures (‘filaments’) in complex assemblies. This work uses Featherstone’s Articulated Body Algorithm to permit 3D simulation of connected assemblies of filaments. It includes development of an elasticity model for filament bending at large angles and a novel multi-body method for simulating the added mass effect. The model’s capabilities are validated through comparison with linear beam dynamics and three experimental studies of fluid–filament interaction from the literature. These are (1) flow-induced reconfiguration of heterogeneous and curved filaments, (2) resonance and flow-induced reconfiguration of filament assemblies and (3), wave-induced dynamics of a filament with added mass. The model is shown to be competitively accurate with existing filament dynamics models while extending modelling capability to multi-stem assemblages. Results from the model application demonstrate the importance of representing complex morphologies for accurately predicting flow-vegetation interactions.