Sharif University of Technology Scientia Iranica 1026-3098 Articles in Press 2025 01 27 Nonlinear modelling and bifurcation analysis of the coupled dynamics of the offshore wind turbine with the tension leg floating platform 23803 10.24200/sci.2025.62717.7996 EN Soheil Ghabraei Department of Mechanical Engineering, Sharif University of Technology, P. O. Box: 11155-9567, Tehran, Iran Hamed Moradi Department of Mechanical Engineering, Sharif University of Technology, P. O. Box: 11155-9567, Tehran, Iran Journal Article 2023 10 01 The present article investigates the coupled nonlinear dynamics of the offshore wind turbine with the floating tension leg platform through numerical methods. The NREL 5MW wind turbine installed on MIT/NREL TLP is chosen as the floating offshore wind turbine. The offshore wind turbine equation of motion is derived using Hamilton's Principle, considering the floating platform surge, heave, and wind turbine's tower transverse motions. The wind turbine tower is modeled using the Euler-Bernoulli beam theory, and the effects of the platform surge and heave motions have been considered. Then, the Galerkin method is applied to the derived partial differential equations of motion of the tower to reduce them to a set of nonlinear ordinary differential equations. Afterward, by utilizing direct time integration, the effects of the frequency and amplitude of wave forcing and the length of the mooring lines on the floating wind turbine's global dynamics are studied. Finally, results are depicted as the frequency response curves and the Poincare maps' bifurcation diagrams. The phase-plane portraits, Poincare maps, and fast Fourier Transforms (FFTs) highlight points of interest in the parameter space. https://scientiairanica.sharif.edu/article_23803_a36a34e762709e56e58e36aee9fd142f.pdf