Time-Domain Analysis of the Hybrid Mooring System with Buoy and Clump Weight on Motions of the Floating Support Platform

Abstract

The safety and stability of mooring systems for floating offshore wind turbines (FOWTs) are crucial for efficient power generation in harsh deep-sea environments. This study examines the hybrid mooring system integrating buoys and clump weights, which show potential in mitigating platform motion responses. A parametric analysis on the OC4-DeepCwind platform with buoy and clump weight is conducted using ANSYS-AQWA, focusing on a multi-segment hybrid mooring system with single buoy and single clump weight (MSM-BSW). The optimal configuration for extreme conditions in the North Sea, MSM-BSW-D, features a buoy radius of 3.5m, a clump weight radius of 3.5m, and a clump weight positioned 40m from the platform. Based on minimal surge motion response variation, a new model featuring multi-segment mooring lines with multi-buoys and multi-clump weights (MSM-MMW) is proposed. The wave-frequency, low-frequency, and total responses of MSM-BSW, MSM-BSW-D, and MSM-MMW under regular wave conditions are compared. Findings show MSM-MMW and MSM-BSW-D perform better in wave-frequency response, with MSM-MMW less sensitive to low-frequency wave loads. Under two wind-wave conditions, MSM-BSW-D and MSM-MMW reduces wave-frequency surge, pitch, and heave motions under operating condition, while the latter has superior performance in parking condition.

Keywords: Buoy and clump weight, Hybrid mooring system, Time-domain motion, Wave-frequency response, Low-frequency response, Total response