EAPSI: A Next-Generation of Wind Fence with Multi-Scale Fractal Structure

了解和控制大气的不稳定性，如风暴引起的突然的空气运动，对研究流体流动的人来说是非常有兴趣的，因为大气湍流的改变可以用来减少强风。因此，了解诸如多孔防风栅栏或防风林等工程结构如何影响各种传入气流是很重要的。本研究将探索多尺度分形结构诱导湍流，以更好地控制气流。该研究将与定量流动可视化、实验流体力学、bluff body空气动力学和生物流体流动方面的专家、浦项理工大学教授Sang Joon Lee合作进行。由于本研究涉及新一代风栅的大气湍流，因此必须有适当的实验室设备来模拟现实条件。主办实验室拥有多个风洞，包括一个大气边界层风洞，以及各种流量测量系统，为开展本研究提供了良好的场所。这项研究的见解将有助于设计更有效的防风栅栏，以限制道路和桥梁等关键基础设施上的雪/沙沉积，并减少风对结构本身的总体影响。先前的研究发现，在平坦表面上，孔隙率为50%的规则单尺度网格栅栏和栅栏高度的10%的底部间隙被认为是最佳的。由于使用该孔隙度标准的分形风栅已经注意到湍流结构的显著差异，因此本研究的目标是推进对大气边界层条件下一维和二维多尺度分形风栅的诱导流动结构和湍流动能输运的认识。具体而言，将采用粒子图像测速（PIV）技术系统地测量分形栅栏周围的整个速度场，以揭示分形栅栏的关键参数对大雷诺数范围内湍流的影响。最终，本研究将有助于新一代分形风栅的设计，该风栅可以从平均风流中提取足够的动能，促进雪/沙的沉积，防止颗粒在过大的湍流应力下再动员。该奖项是与韩国国立研究财团合作设立的。

Understanding and controlling atmospheric instabilities, such as abrupt air movements resulting from a storm, is of great interest to those who study fluid flow as alterations of atmospheric turbulence can be used to reduce strong winds. It is important, therefore, to understand how engineered structures such as porous wind fences or windbreaks affect various incoming flows. This research will explore multi-scale fractal structure-induced turbulence to better control air currents. The research will be conducted in collaboration with Professor Sang Joon Lee of Pohang University of Science and Technology (POSTECH), an expert in quantitative flow visualization, experimental fluid mechanics, bluff body aerodynamics and bio-fluid flows. Because this study is concerned with atmospheric turbulence for new-generation wind fences, it is imperative to have the appropriate laboratory equipment to simulate real-life conditions. The host laboratory has multiple wind tunnels, including an atmospheric boundary-layer wind tunnel, and various flow measurement systems, providing an excellent location to conduct this research. Insights from this research will contribute to engineering more effective wind fences to limit snow/sand deposition on critical infrastructure such as roads and bridges and to reduce the overall side impact of wind on structures themselves.Previous studies found that a regular mono-scale grid fence of 50% porosity and a bottom gap of 10% of the fence height are considered to be optimal over a flat surface. Since significant differences in turbulent structure have been noted using fractal wind fences with this porosity criteria, the goal of this research is to advance knowledge on the induced flow structure and the turbulence kinetic energy transport of 1D and 2D multi-scale fractal fences in atmospheric boundary-layer conditions. Specifically, whole velocity fields will be systematically measured around the fractal fences by Particle Image Velocimetry (PIV) techniques to uncover effects of key parameters of fractal fences on turbulence for a wide range of Reynolds numbers. Ultimately, this research will assist design of new-generation fractal wind fences which can extract sufficient kinetic energy from the mean wind flow to promote snow/sand deposition and prevent particle remobilization from excessive turbulent stresses. This award is funded in collaboration with the National Research Foundation of Korea.