帆船整体空气动力性能的数值模拟

  目的  柔性风帆在风载荷下易发生非线性大变形，风帆形状会影响风帆周围的气流特性，为此研究柔性风帆变形对空气动力学性能的影响。  方法  开展柔性风帆变形的流固耦合研究。建立柔性风帆的初始形状模型和材料模型，采用显式有限元分析程序AUTODYN解决柔性风帆非线性大变形问题，构建变形后的风帆形状。利用STAR-CCM+软件预测初始风帆和变形风帆性能。  结果  结果表明，相对风向角为20°的逆风条件下，变形风帆的迎风面整体压力值增大，背风面后缘附近产生的流动分离更严重，拱度增大带来的升力增大效应相对较小，因此升力整体减小。  结论  柔性风帆变形的流固耦合研究适用于精确评估或者优化风帆性能。

Full-scale flying shape measurement of offwind yacht sails with photogrammetry

  Objective  The shape of a sail influences the airflow characteristics around it, and flexible sails are prone to large nonlinear deformation under wind pressure. As such, this paper studies the effects of sail deformation on aerodynamic performance.  Methods  A fluid-structure interaction (FSI) study on flexible sail deformation is performed. The initial shape model and material model of a sail are established, an explicit finite element method (FEM) such as AUTODYN is applied to calculate the large nonlinear deformation of the sail, and the shape of the deformed sail is constructed. STAR-CCM+ is applied to predict the performance of the initial and deformed sail.  Results  The results show that positive pressure on the windward side of the deformed sail increased, and the flow separation generated around the leeside of the sail leech became more severe in upwind conditions with a relative wind angle of 20°. The increase of the lift force due to the rise of the camber was relatively small, resulting in a decrease in overall lift force.  Conclusion  FSI studies on flexible sail deformation are suitable for the precise evaluation or optimization of sail performance.