Insights into the aerodynamic response of a harmonic oscillating airfoil in various turbulent flows.

Abstract

The general theory of aerodynamic instability and the mechanism of flutter has been applied for decades in the environmental condition of uniform flow. Given the substantial growth in wind energy technology and aerospace in recent decades, there has been a greater focus on exploring the aerodynamic performance of oscillating airfoils in the environment of turbulence rather than just uniform flow. Most current research remains based on aerodynamic models obtained from potential flow theory, which have been thoroughly demonstrated through experimentation to be effective under the condition of uniform flow. However, it is still unclear whether turbulence and its interaction with the airfoil will cause traditional aerodynamic models to breakdown and how it will change under turbulent conditions. This study presents an analysis of how turbulence intensities and scale ratios individually influence the characteristics of oscillating airfoils. Furthermore, the turbulent kinetic energy and correlation are intimately associated with these two main components. The results suggest that as the turbulence intensities increase, more energy is injected, resulting in a larger amplitude of unsteady lift. In turbulence, smaller scale ratios reduce correlation and result in a decrease in the amplitude of lift. Turbulence could also lead to a departure of the transfer function from its theoretical value, known as the Theodorsen function. This work examines and evaluates the influence of turbulence on oscillating airfoils. The results might serve as a foundation for aerodynamic analysis to examine the stability of airfoils in turbulent flows.