CAREER:On the Coupled Nature of Highly-Flexible Plates Subjected to Fluid Loads: An Exploration of Structural Response and Reconfiguration

鳐鱼在海洋中的游动运动涉及到两个柔性鳍的扇动。由于翅片形状的改变，周围的流场也随之改变。这种流体-结构相互作用的另一个例子是海草。在水流中，海草会随着水流弯曲，变成流线型。这些灵活的结构可以减少净阻力。该项目从这两个例子中获得灵感，其目标是确定在空气-水界面附近高度柔性板的形状重新配置后流场如何变化。减少阻力也将通过主动控制板刚度来证明。这项工作的结果有可能改善推进方法和混合过程。这个项目的另一个组成部分包括一年一度的中学生暑期教育计划，包括小型桌面实验。当地的本科生和高中生也将有机会参与这项研究。本研究项目的目标是了解靠近自由表面的高度柔性板的流固相互作用。需要制定标度定律来解释由于靠近自由表面的板的重新配置而导致的阻力系数的减少。这些标度定律将主要通过实验来实现，并与理论和模拟进行比较。粒子图像测速测量将得到速度和压力。立体数字成像和高速摄影将用于测量水-结构界面处的板挠度。板上的压力和力传感器将测量流体载荷。一种基于水接触线测量的新方法与理论相结合，可以预测板上的压力，而无需使用传统的压力传感器人为地使板变硬。该项目将促进我们对高柔性板周围流动的理解，因为：1)自由表面的影响；2)垂直振荡运动，即周期性改变方向的绕体流动；3)垂直振荡运动和前进速度的结合；4)主动控制板刚度以达到预定的流动条件。通过利用主动和被动结构重新配置，可以潜在地减少波动推进器和船舶的阻力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The swimming motion of rays in the ocean involves the flapping of two flexible fins. As a result of the fins changing shape, the surrounding flow field is altered. Another example of this type of fluid-structure interaction is that of seagrass. In a current, the seagrass will flex and become streamlined with the flow. These flexible structures cause a net reduction in drag. This project takes inspiration from these two examples with its goal being to identify how the flow field changes as a result of the shape reconfiguration of a highly flexible plate near an air-water interface. Drag reduction will also be demonstrated by actively controlling the plate stiffness. The results of this work have the potential to improve propulsion methods and mixing processes. Another component of this project includes an annual summer educational program for middle school students, complete with small table-top experiments. Local undergraduate and high school students will also have an opportunity to participate in this research.The goal of this research project is to understand the fluid-structure interaction of a highly flexible plate near a free surface. Scaling laws will need to be developed to explain the reduction in drag coefficient due to the reconfiguration of the plate in the proximity of the free surface. These scaling laws will be achieved primarily through experimentation and compared with theory and simulation. Particle image velocimetry measurements will yield velocities and pressures. Stereoscopic digital imaging and high-speed photography will be used to measure plate deflections at the water-structure interface. Pressure and force sensors on the plate will measure fluid loads. A new method based on measurements of the water-contact line along with theory will allow for the prediction of the pressure on the plate without artificially stiffening the plate with traditional pressure transducers. The project will advance our understanding of flow around a highly flexible plate due to: 1) the influence of the free-surface, 2) vertical oscillatory motion, i.e. flow around the body that periodically changes directions, 3) the combination of vertical oscillatory motions and forward speed, and 4) active control of the plate stiffness to attain pre-defined flow conditions. By leveraging active and passive structural reconfigurations, drag can potentially be reduced on undulatory propulsors and vessels.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.