Aerodynamic characteristics of airfoils with fractal structures in low-Reynolds-number regimeAerodynamic characteristics...J. Li et al.

This study investigates the aerodynamic characteristics of airfoils partially equipped with fractal structures (“fractal airfoils”) in the low-Reynolds-number regime. Wind tunnel experiments are conducted using symmetric and frat airfoils under both steady and unsteady conditions. The aerodynamic performance is examined with measurements of the lift and drag forces and flow visualization using the smoke-wire method. The results are compared with airfoils partially equipped with slits to produce the same porosity (“slit airfoils”). The results show that fractal structures significantly influence the flow characteristics around the airfoil and lift and drag forces. The lift-to-drag ratio, Cl/Cd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_\textrm{l}/C_\textrm{d}$$\end{document}, of the fractal airfoil is higher than that of the slit airfoil for low angles of attack at lower Reynolds number. The fractal parts effectively reduce the occurrence of a dynamic stall in unsteady conditions, resulting in a more stable Cl\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_{\rm l}$$\end{document} curve. The results suggest that fractal structures have significant potential in future aviation applications.