李昂, 孙仁()

上海交通大学 工程力学系; 水动力学教育部重点实验室, 上海 200240

收稿日期:2020-07-27出版日期:2021-08-28发布日期:2021-08-31
通讯作者:孙仁E-mail:drrsun@sjtu.edu.cn
作者简介:李 昂(1990-),男,河北省沧州市人,博士生,现主要从事流体力学研究
基金资助:国家自然科学基金(11672182);教育部博士点基金(20130073110059)

Hydrodynamics Study of Riser with Helical Strakes Oscillating in Flow

LI Ang, SUN Ren()

Department of Engineering Mechanics; Key Laboratory of Hydrodynamics of the Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China

Received:2020-07-27Online:2021-08-28Published:2021-08-31
Contact:SUN Ren E-mail:drrsun@sjtu.edu.cn

摘要/Abstract

摘要： 为了减小立管受到的振动损伤,本文对无列板立管以及三螺旋对称分布列板立管的水动力参数进行了实验评估.自然环境中的波浪与来流被抽象为振荡流与均匀流叠加,实验工况分为静止流场和相对运动流场.同时,立管受迫振动方向分别为流场纵向、横向以及纵向45° 夹角.结合Morison公式,由实验数据计算得到立管的附加质量系数C_m和托曳力系数C_d.实验结果表明,带螺旋列板立管的C_m与Keulegan-Carpenter(KC)数无关,C_m与受迫振动方向无关;C_d与流场速度和振动最大速度间的比率以及KC数的1/3次幂成反比关系.该发现与经典理论振荡流中平板结构Morison参数的形式相吻合,使经典理论在立管设计中获得新的验证与应用.在相同条件下,带螺旋列板立管的C_d值平均高出光滑立管273%.该发现表明在复杂工况下,螺旋列板能有效降低振动造成的影响.该结果可为海洋结构物的消振设计提供新的思路, 在海洋工程领域具有较高的应用价值.
关键词: 水动力学, 螺旋列板, 立管, 振动
Abstract: To reduce the vibration damage to the riser, hydrodynamic parameters of a smooth riser and a riser with triple symmetrically distributed helical strakes are evaluated in an experiment. The wave and current in natural environment are conceptualized to the experimental condition of the oscillatory flow and the uniform flow. Experiment cases are divided into the static flow and the uniform flow, while the risers oscillate along the in-line, the transverse, and the diagonal direction. The added mass coefficient C_m and the drag coefficient C_d are calculated from experimental data by using the Morison equation. The results of the riser with strakes indicate that C_m is independent of the Keulegan-Carpenter (KC) number and the oscillating direction. C_d is found to be in inverse proportion to the ratio of 1/3 power of the KC number and the maximum flow speed to oscillatory velocity. This finding is consistent with the format of Morison parameters of a flat plate in oscillatory flow, which endows the classical theory with novel validation and implication in the design of a riser. Under the same condition, the C_d of the helical strake riser is promoted over 273% than the bare riser, which indicates that the helical strakes efficiently reduce the influence of oscillation under complex conditions. The results provide a new solution for vibration reduction of offshore structures, which is of high value in ocean engineering.
Key words: hydrodynamics, helical strakes, riser, oscillation


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