Numerical flow analysis of vertical axis wind turbines with morphing airfoils

变形翼型有能力改变其几何形状，以优化特定操作流条件下的空气动力。当应用于垂直轴风力涡轮机（VAWTs）时，这项技术可以非常有效，因为这些涡轮机的叶片在旋转时会遇到不同的迎角。变螺距技术在过去已经研究了相同的目的，但它在机械上更难实现，并提供比变形翼型更少的灵活性。变形形状的控制更容易实现，并且具有优化每个叶片产生的瞬时扭矩的更大潜力。提出的研究将调查变形翼型，改变几何形状的后缘，因此弧度线的翼型。改变几何形状可用于防止动态失速，增加旋转背风部分的功率提取，在旋转周期内分配负载或作为断裂系统。本研究计划提出了一种方法来理解变形几何的影响，特别是在动态失速期间。它还包括一个计算工具的开发，用于预测VAWT对不同变形策略提取的功率。****计算流体动力学技术是模拟复杂几何形状周围流体流动的强大工具。大涡模拟（LES）是研究动态失速等复杂非定常流场的必要模型，但计算成本较高。多年来，Paraschivoiu教授的研究小组开发了内部LES-CFD代码，并对vawt进行了验证。当前提案的目标是进一步发展数值算法和软件，并使用这些来分析变形风力涡轮机叶片的流动，以及动态失速。研究的其他重要方面将是研究改进的LES模型和增加新的加速技术，这将减少LES通常需要的大量计算时间。*********

A morphing airfoil has the ability to change its geometry in order to optimize the aerodynamic forces for a specific operating flow condition. This technology can be very effective when applied to vertical axis wind turbines (VAWTs), because the blades of these turbines encounter different angles of attack as they rotate. Variable pitch technology has been investigated in the past for the same purpose, but it is mechanically more difficult to implement and offers less flexibility than morphing airfoils. Control of the morphing shape is easier to implement and has a greater potential for optimizing the instantaneous torque generated by each blade. The proposed research will investigate morphing airfoils that change the geometry of the trailing edge, and therefore the camber line of the airfoil. Changing the geometry can be used to prevent dynamic stall, to increase power extraction in the leeward portion of the rotation, to distribute the load over the rotation cycle or as a breaking system. This research plan proposes an approach to understand the influence of morphing the geometry, in particular during dynamics stall. It also includes the development of a computational tool for predicting the power extracted by a VAWT for different morphing strategies.****Computational Fluid Dynamics techniques are powerful tools to simulate fluid flow around complex geometries. Although computationally expensive, Large Eddy Simulation (LES) is a necessary model to study complex unsteady flows such as the one occurring during dynamic stall. Over the years, an in-house LES-CFD code has been developed by Prof. Paraschivoiu's research group, and validated for VAWTs. The objective of the current proposal is the further development of the numerical algorithms and software, and to use these to analyze flow over morphing wind turbine blades, as well as dynamic stall. Other important aspects of the research will be the investigation of an improved LES model and addition of new acceleration techniques that will reduce the significant computation time that LES typically requires.*********