• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Analysis of bio-inspired propulsors.
【24h】

Analysis of bio-inspired propulsors.

机译：生物启发推进器的分析。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The locomotion of fish and aquatic animals is achieved by the oscillation of fins and flukes, which creates highly three-dimensional, unsteady flow fields that are not yet well-understood. The principal non-dimensional parameter presently used to describe these flows is the Strouhal number, St = fA/U, which depends on the frequency of oscillation ( f), the width of the wake (A), and the freestream velocity (U). In previous work on two-dimensional foils, wake structure and thrust performance have been shown to scale with this parameter, but it does not include considerations of three-dimensionality, which become important in the study of low-aspect ratio propulsors. In the current work, a new nondimensional scaling parameter is proposed which, for a rigid rectangular pitching panel, collapses measurements of pressure, thrust, and circulation when plotted again Strouhal number.;Dye flow visualization and Digital Particle Image Velocimetry (DPIV) were used to investigate the wakes of rigid pitching panels with a trapezoidal panel geometry, chosen to model idealized fish caudal fins. A Lagrangian Coherent Structure (LCS) analysis was employed to investigate the formation and evolution of the panel wake. The LCS analysis, based on calculations of the Direct Lyapunov Exponent (DLE) has several advantages over Eulerian methods, including greater detail and the ability to define structure boundaries without relying on a preselected threshold. A bifurcation of the LCS structure in the wake of the trapezoidal pitching panels coincided with an observed transition of the wake structure. Also, the LCS analysis provided evidence of the "trapping" of vortices on trapezoidal panel surfaces with low sweep angles or at low Strouhal numbers.
机译：鱼和水生动物的运动是通过鳍和的振荡来实现的，鳍和creates的振荡产生了高度三维的，不稳定的流场，这些流场尚未得到很好的理解。当前用来描述这些流动的主要无量纲参数是Strouhal数St = fA / U，它取决于振荡频率（f），尾流宽度（A）和自由流速度（U） 。在先前对二维箔片的研究中，尾流结构和推力性能已显示出与此参数成比例的关系，但其中不包括对三维度的考虑，这在研究低长宽比推进器中变得很重要。在当前的工作中，提出了一个新的无量纲缩放参数，该参数对于刚性的矩形变桨面板，在再次绘制斯特劳哈尔数时会破坏压力，推力和环流的测量结果。调查具有梯形面板几何形状的刚性俯仰面板的尾迹，选择该模型来模拟理想的鱼尾鳍。拉格朗日相干结构（LCS）分析用于调查面板尾流的形成和演化。基于直接李雅普诺夫指数（DLE）的计算，LCS分析相对于欧拉方法具有多个优势，包括更详细的信息以及无需依赖预选阈值即可定义结构边界的能力。在梯形变桨面板的尾流中，LCS结构的分叉与尾流结构的观察到的过渡相吻合。而且，LCS分析提供了在低扫角或低Strouhal数的梯形面板表面上“捕获”涡旋的证据。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号