基于VOF法的水下管阀结构水动力系数特性研究

水下结构物结构行为及运动响应规律预测的基础是精确获取结构物水动力系数。鉴于此,以二维简化水下管阀为研究对象,通过VOF模型捕捉自由液面以及重叠网格技术模拟结构物在水面附近的强迫振荡运动,对管阀结构的附加质量系数与阻力系数特性进行系统研究。研究结果表明:附加质量系数及阻力系数受Kc数的影响较大,前者随着Kc的增大而增大,后者与之相反,振荡频率对附加质量系数影响较小,两者基本相互独立;附加质量系数随着管阀长度比的增大而逐渐增大,而管阀长度比对阻力系数的影响较小,两者基本相互独立;管阀高度比对附加质量系数与阻力系数的影响均较小,水动力系数仅受Kc数的影响。所得结论对水下结构物下放安装过程中结构行为及运动规律的精准预测具有指导作用。

VOF-based Study on Characteristics of Hydrodynamic Coefficients of Subsea Pipe-Valve Structures

The structural behavior of a subsea structure and the prediction of its motion response laws are the basis to accurately determine its hydrodynamic coefficient.Taking the simplified two-dimensional(2D)subsea pipe-valve as the research object,a systematic study had been made to the added mass coefficient and drag coefficient of the pipe-valve structure by capturing the free liquid surface with the volume of fluid(VOF)model and simulating the near-surface forced oscillation motions of the structure with the overlapping grid technique.Results indicate that the added mass coefficient and drag coefficient are strongly influenced by the Kc number,the former will increase with Kc,while the latter is the opposite;the oscillation frequency has little influence on the added mass coefficient,both of which are basically independent of each other;the added mass coefficient will gradually increase with the length ratio of the pipe-valve,while the length ratio of the pipe-valve has little influence on the drag coefficient,both of which are basically independent of each other;the height ratio of the pipe-valve has little influence on both the added mass coefficient and drag coefficient,while the hydrodynamic coefficient is only influenced by the Kc number.Such a conclusion will guide the structural behaviors during the lowering and installation of a subsea structure and the accurate forecast of its motion laws.