Experimental Study on the Wave Run-Up Properties and Slamming Loads of a Four-Column Floating Wind Turbine System

Abstract China Offshore Oil Engineering Cooperation (COOEC) has constructed a semisubmersible floating wind turbine system in South China Sea. It is designed to withstand extreme sea state, horizon cyclone with a return period in 50 years. In addition to conventional design criteria, maximum inclination and acceleration, wave run-up and slamming loads also challenge the safety operation and integrity of the structure. A scaling mode test was conducted for these nonlinear-hydrodynamic domain issues. Wave run-up phenomenon is categorized into three groups based on the test observation, namely, climb-up, white water and green water. The climb-up is accepted in design due to its low load level and water entry. The white water could be tolerated if the structure withstands slamming loads, while the green water must be prevented due to its unexpected large loads. For the evaluation of slamming loads, a numerical method is proposed based on calibration result. The wave surface elevation near the platform is calibrated using the test result, and then the water particle velocity is determined by partial differentiation of the free surface boundary condition. The slamming pressure is consequently obtained using conventional formulas and empirical coefficients. The proposed wave run-up design procedure and slamming loads calculation method provide a basic reference for floating wind turbine design allowing for a smaller margin compared to widely accepted methods used in offshore oil and gas projects.