半潜式浮式风机平台绕流力学特性与尾流分析

柱体绕流是海洋工程领域的重要问题.流体绕经海洋平台所产生的周期性涡脱会造成平台往复运动,这将加剧平台系泊结构疲劳损伤,降低结构疲劳寿命.为研究多柱式浮式风机平台绕流的力学特性,厘清尾流之间的干扰机理,采用Delayed Detached Eddy Simulation(DDES)方法分析了半潜式浮式风机平台在不同来流角和流速下的力学特性,从相干结构层面研究了尾流干扰机理,并分析了立柱尾流之间的空间相关性.结果表明:下游立柱的阻力系数平均值随流速变化而有较大波动;流场相干结构以流向涡和发夹涡为主;相干结构之间的相互作用是导致尾流干扰的原因;上下游立柱尾流具有不同的相干结构,但两者仍有较强的空间相关性.研究结果可为深入理解多柱式海洋平台绕流现象提供理论参考.

Mechanical Characteristics and Wake Analysis of Flow past a Semi-submersible Floating Wind Turbine Platform

Flow past cylinders is an important issue in ocean engineering. Periodical vortex shedding occurring around the offshore platform in current leads to reciprocating motion of the offshore platform, which may aggravate the fatigue damage and thus cause the reduction of fatigue life of the moorings. In order to study the mechanical characteristics of flow past multi-column floating wind turbine platform and understand the mechanism of wake interference clearly, numerical simulations were performed using Delayed Detached Eddy Simulation (DDES). The effects of headings and current velocities on the mechanical characteristics of the semi-submersible floating wind turbine platform were investigated. The mechanism of wake interference was studied from the level of coherent structures, and spatial correlation between different wakes behind the columns was also investigated. The results demonstrate that: (1) the average drag force coefficient of downstream column has a large fluctuation with the change of current velocity; and streamwise vortex and hairpin vortex are the main coherent structures; (2) the interaction between coherent structures results in wake interference; (3) the upstream wake and the downstream wake have strong spatial correlation, but their coherent structures are different. The research results provide a theoretical reference for understanding the phenomenon of flow past multi-column offshore platform.