International Journal of Naval Architecture and Ocean Engineering

The Society of Naval Architects of Korea (대한조선학회)
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Estimation of damping induced by taut mooring lines

  • Xiong, Lingzhi (State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University) ;
  • Lu, Wenyue (State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University) ;
  • Li, Xin (State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University) ;
  • Guo, Xiaoxian (State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University)
  • Received : 2019.07.08
  • Accepted : 2019.12.19
  • Published : 2020.12.31
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Abstract

A moored floating structure may exhibit resonant motion responses to low-frequency excitations. Similar to the resonant responses of many vibration systems, the motion amplitude of a moored floating structure is significantly affected by the damping of the entire system. In such cases, the damping contributed by the mooring lines sometimes accounts for as much as 80% of the total damping. While the damping induced by catenary mooring lines is well-investigated, few studies have been conducted on the damping induced by taut mooring lines, especially one partly embedded in soil. The present study develops a simple but accurate model for estimating the damping contributed by mooring lines. A typical type of taut mooring line was used as the reference and the hydrodynamic drag force and soil resistance were taken into consideration. The proposed model was validated by comparing its predictions with those of a previously developed model and experimental measurements obtained by a physical model. Case studies and sensitivity studies were also conducted using the validated model. The damping induced by the soil resistance was found to be considerably smaller than the hydrodynamic damping. The superposition of the wave frequency motion on the low-frequency motion was also observed to significantly amplify the damping induced by the mooring lines.

Keywords

Acknowledgement

This work was financially supported by the National Natural Science Foundation of China (Grant no. 51709169) and the open foundation of State Key Laboratory of Ocean Engineering (Shanghai Jiao Tong University) (Grant No. 1618).

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