Hydrokinetic flapping foil turbines in swing-arm mode have gained considerable interest in recent years because of their enhanced capability to extract power, and improved efficiency compared to foils in simple mode. The performance of foil turbines is closely linked to the development and separation of the Leading-Edge Vortex (LEV). To accurately model the formation and the separation of the LEV on flapping foils, a purpose-built 2D numerical model was developed. The model is based on the weighted residual Finite Element Method (FEM); this is combined with an interface capturing technique, Level-Set Method (LSM), which was used to create a reliable and high-quality numerical solver suitable for hydrodynamic investigations. The solver was validated against well-known static and dynamic benchmark problems. The effect of the mesh density was analyzed and discussed. This paper further covers an initial investigation of the hydrodynamics of flapping foil in swing-arm mode, by studying the structure of the vortex around a NACA0012 foil. The presented method helps to provide a better understanding of the relation between the Leading-Edge Vortex creation, growth, and separation over the flapping foil in swing-arm mode and the extracted power from a hydrokinetic turbine.

翻译：水动力扑动翼涡轮机在摆臂模式下因相比简单模式具有更强的能量提取能力和更高的效率，近年来引起了广泛关注。翼型涡轮机的性能与前缘涡的形成和分离密切相关。为精确模拟扑动翼上前缘涡的形成与分离过程，本研究开发了一种专门构建的二维数值模型。该模型基于加权残值有限元法，并结合界面捕捉技术——水平集方法，创建了一个可靠且高质量的数值求解器，适用于水动力学研究。该求解器已通过知名静态和动态基准问题的验证，并分析讨论了网格密度的影响。本文进一步通过研究NACA0012翼型周围的涡结构，初步探究了摆臂模式下扑动翼的水动力学特性。所提出的方法有助于更深入地理解摆臂模式下扑动翼上前缘涡的产生、生长和分离与水动力涡轮机能量提取之间的关系。