基于准动态模型的提油作业拖轮适用性分析

Research on suitability of tug for offloading in tandem between FPSO and shuttle tanker based on quasi-dynamic model

目前,由于串靠外输方式具有对船舶吨位差异及装载状况要求小、海况适应力强、系泊力小、解脱迅速等优点,而被广泛运用于浮式生产储卸油平台(FPSO)外输作业中。串靠提油作业时,位于穿梭油轮尾部的拖轮能够提供的最大有效拖力直接影响到了作业的安全性。为完善串靠提油作业时所需拖轮拖力的研究,提出更加合理的拖轮选型理论依据,就需要对拖力进行数值计算。首先,对FPSO与穿梭油轮串靠外输系统绕系泊单点旋转时所受风、浪、流等环境载荷进行全面考虑,建立了准动态受力平衡模型;然后,运用经验公式及AQWA软件计算出环境载荷大小,并依据计算结果拟合出环境载荷曲线;最后,配合受力平衡方程求解出能够保障作业安全进行所需的最小拖力。依照此方法计算所得拖力选取的拖轮能够兼顾作业安全性和使用经济性。

At present,the offloading in tandem between FPSO and shuttle tanker,which needs little mooring force and can well adapt to different ship tonnages,loading conditions and complexity of the marine environment,has been widely used. During the offloading operation in tandem,the maximum available towing force,provided by the stern tug,has immediate impact on operation safety. In order to perfect the study of required towing force in offloading operation in tandem and put forward a more reasonable theoretical basis for tug selection,the towing force is calculated in this paper. Environmental loads,such as winds,waves and flow,are comprehensively considered,while FPSO and shuttle tanker are circling around the single point. A quasi dynamic equilibrium model is set up and the value of environmental loads is obtained by use of empirical formulas and AQWA-Workbench tools. Finally,by fitting the environmental load curves and using force balance equations,the required minimum towing force for operation safety is calculated. Both operational safety and economical efficiency can be aligned by this towing force to select tug.