基于CFD的FPSO风载荷规范计算适用性研究

Applicability study of rules for wind load calculation of FPSO based on CFD

  • 摘要:
    目的 目前,设计人员多使用针对大型油轮的OCIMF规范和针对海上平台的API规范对FPSO风载荷进行计算,但因FPSO船舶上层建筑更为复杂,需进一步研究这2种规范对于FPSO风载荷计算的适用性。
    方法 建立具有通用型上部模块的某30万吨级大型FPSO数值模型,对恶劣海况下不同风向角、横倾角下的FPSO所受风载荷进行数值模拟,分析其中存在的遮蔽效应;与规范计算结果进行对比分析,讨论在风载荷作用下FPSO受到的横倾力矩。
    结果  结果显示,船舶正浮状态受到的最大风载荷和横倾力矩出现在270°风向角;船舶横倾状态下受到的风载荷和横倾力矩比正浮状态更大,最大横倾力矩出现在10.5°横倾角280°风向角;采用API规范和OCIMF规范得到的FPSO风载荷计算结果与CFD计算结果相差较大,二者在270°风向角的结果与CFD分别相差13.6%和24.5%。
    结论 数值仿真给出的流场细节有利于分析上部模块间的遮蔽效应,能够较为准确地预报船舶所受到的风载荷,可以为考虑遮蔽效应的FPSO稳性设计提供参考。

     

    Abstract:
    Objective  At present, the oil companies international marine forum (OCIMF) rules are frequently used to calculate wind load for large tankers and the American petroleum institute (API) rules for offshore platforms. However, due to the complexity of floating production storage and offloading (FPSO) superstructures, whether these two sets of rules can be applied to the wind load calculation of FPSO requires further study.
    Methods This paper establishes a numerical model of a 300 000-ton class FPSO with a universal superstructure. The wind load on the FPSO under severe sea conditions and different wind angles is calculated and compared to the results of the rules. The shielding effect and heeling angle of the FPSO are analyzed.
    Results The maximum heeling moment and wind load under an upright floating attitude appear at a 270° wind angle. The heeling moment and wind load under a heeling floating attitude are greater than those under an upright floating attitude, and the maximum heeling moment appears at a 10.5° heeling angle and a 280° wind angle. The results of the API and OCIMF rules show big differences compared with CFD: the differences between their results at a 270° wind angle and CFD are 13.6% and 24.5% respectively.
    Conclusion  The flow field details obtained by numerical simulation are conducive to analyzing the shielding effect between superstructures and enhancing the accuracy of ship wind load prediction, thereby providing valuable references for the stability design of FPSO.

     

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