柔性振荡翼水动力学特性及其在海流能量采集系统中的应用研究

The purpose of this project is to study the fundamental flow phenomena in oscillating-based ocean renewable energy generator by Computational Fluid Dynamics (CFD) method as well as hydrodynamic experiments. It will provide essential insight into the benefits of employing new concepts of optimization methods like using flexible wings or multi-wings to improve existing industry design and develop new prototypes..In recent years, a new class of bio-inspired current energy devices based on oscillating wings is being developed rapidly due to their environmental friendliness and comparable efficiency compared to the conventional rotational energy extraction devices. The energy is extracted by the oscillation motion of wing which imitates the reversed thrust generation process by animals flying and swimming. The prime interest from the design point of view is the determination of system hydro/structural dynamic operation parameters to achieve optimal energy output and efficiency under real-life flow and structure conditions. An improved understanding of the flow mechanisms underlying the complex interaction between the device and the surrounding fluid is critical to assess the hydrodynamic performance of these devices and thus to reduce the overall system cost. Moreover, some optimization methods or performance improvement strategies could be taken into consideration, such as involving flexible wings or using double or multiple wings arrangement. Before the engineering application, the hydrodynamic mechanisms of this kind of optimization method must be analyzed in detail. The stiffness distributions on the wings, the high Reynolds number, the parameters such as aspect ratio and wing shape, and the kinematic and dynamic parameters that are directly connected to the energy harvesting process will be systematically investigated, due to their effects on flow separations on the wings, vortical and member's interactions, hydrodynamic forces, and performance or efficiency..Current research studies are based on the simple model due to the complexity of numerical modeling challenges. For the first time, the effect of flexibility and stiffness of wings on the power extraction will be examined. Furthermore, we will model multi-wing energy converter by considering hydrodynamic interaction between members and the dynamic response of the system to unsteady loading. In a short term, successful outcome of the numerical studies will feed into the operational control of a scaled prototype designed for hydrodynamic mechanism validation. In a longer term, the project will deliver a fundamental advance in ocean renewable energy modeling capability in the wide range of renewable energy industry.

本项目主要目标是研究基于振荡翼的海流能量采集系统中流体力学机理问题，研究手段是计算流体力学方法及水动力学试验，主要创新点是引入了柔性翼、多翼组合的性能优化方式，其结果将有望提高现有系统的效率以发展新一代的海流能量采集装置。近年来，一种新的从仿生概念出发的、基于振荡翼的海流能量采集系统得到迅速发展，其主要优点是相比于传统旋转浆片系统的环境友好性与较高的采集效率。本项目将从水动力学机理、真实工况下的系统可操作性及效率出发，研究其中复杂的流体与结构的流固耦合现象。进一步，引入柔性翼及多翼组合的性能优化方式，详细研究高雷诺数效应、翼面形状与展弦比、系统的运动学及动力学参数，这些参数将直接影响水翼表面的流动分离、水动力特性与性能。本项目首次考虑柔性翼、多翼组合方式对海流能量采集系统的性能影响，短期目标将建立缩比的小尺寸水动力学原理样机，长期目标是将这些性能优化方法应用到产业界。

近年来，一种新的从仿生概念出发的、基于振荡翼的海流能量采集系统得到迅速发展，其主要优点是相比于传统旋转浆片系统的环境友好性与较高的采集效率。本项目将从水动力学机理、真实工况下的系统可操作性及效率出发，研究其中复杂的流体与结构的流固耦合现象。进一步，详细研究高雷诺数效应、翼面形状与展弦比、系统的运动学及动力学参数，这些参数将直接影响水翼表面的流动分离、水动力特性与性能。本项目围绕基于振荡翼的海流能量采集系统，对相关的流固耦合机理问题进行了系统研究。为了揭示拍动翼流场特性的一般规律，首先对拍动翼尾流二维到三维的转捩特性、静止流场中椭圆翼上下振动导致的对称性破坏等进行了研究。研究方法为线性稳定性分析结合三维直接数值模拟。进而对几种类型的拍动翼海流能量采集装置进行了系统的参数研究，包括展弦比对全主动拍动翼海流能采集系统影响；惯性以及非正弦转动对半主动拍动翼海流能采集系统的影响；自由面对拍动翼海流能采集系统的影响；全被动拍动翼海流能采集系统在参数空间内的流动规律及能量采集性能。最后设计了一种基于拍动翼的海流能量采集系统样机，在没有外界调制电机介入时，可视为全被动系统。