Bio-inspired semi-submersible platform for improving the hydrodynamic stability of floating vertical-axis wind turbines

Floating vertical axis wind turbines (VAWTs) offer high power density, directional insensitivity and convenient operation and maintenance; however, their large power fluctuations and limited survivability under extreme sea states hinder utility-scale deployment. To address these challenges, this study proposes a water hyacinth (WH)-inspired semi-submersible platform incorporating biomimetic buoyancy chambers parameterized using Bézier curves. Three configurations (WHS, WHM, and WHL) are developed and evaluated using a Dynamic Fluid-Body Interaction (DFBI) approach coupled with a Volume of Fluid (VOF) model under combined wind-wave loading. The biomimetic geometry modifies the added-mass distribution, hydrodynamic damping, and local flow structures around the platform, leading to reductions of up to 16.3%, 15.5%, and 15.0% in the dominant surge, heave, and pitch responses, respectively. Among the three configurations, WHM exhibits the most balanced hydrodynamic performance. Further comparisons with spherical, cylindrical, and disc-shaped buoyancy structures of equivalent volume demonstrate that the improved stability originates from the biomimetic morphology rather than buoyancy enhancement alone. When integrated into a floating VAWT system, the WHM platform reduces surge, heave, and pitch responses by 0.8%, 11%, and 10%, respectively, while decreasing the power spectral density of the power coefficient by approximately 18.6%. Overall, the proposed WH-inspired platform provides an effective passive strategy for improving the hydrodynamic stability and smoothing power output of floating VAWTs.