To investigate the dynamic characteristics of tension leg platform (TLP) under coupled wind-waves effect

this paper proposes an optimal mooring diameter suitable at the average water depth in the East China Sea. Taking the NREL (National Renewable Energy Laboratory) 5 MW offshore wind turbine and TLP as research subjects

a Kaimal turbulent wind spectra and P-M irregular wave spectra are generated according to the IEC 61400-3 standard. The effects of mooring diameter

wind-wave misalignment angle

and water depth on the TLP are analyzed systematically according to the guidelines of offshore floating wind turbine platforms for the China Classification Society. The mooring diameter is optimized by using the Gaussian mixture model (GMM) and the expectation maximization (EM) iterative method. It is found that as mooring diameter and wind-wave misalignment angle increase

the initial position and displacement amplitude of TLP in surge and sway directions both decrease obviously. When the direction of wind and waves are misaligned

the platform motion component is consistent with the surge direction but opposite to the sway direction. Moreover

as the wind-wave misalignment angle increases

the sway response becomes more sensitive

and the roll motion first increases and then declines slowly. Additionally

as the ocean depth increases

the peak of surge displacement increases significantly

while the yaw direction is not obvious. The optimal mooring diameter at seawater depths between 300 m and 370 m is 0.134 m. This study provides a theoretical guidance of design optimization

performance evaluation

and large-scale development for the TLP and mooring systems in China’s offshore region.