Numerical Investigation of Stall Characteristics and Stall Control of Circulation Control Airfoil

In recent years, circulation control (CC) technology has garnered significant attention in the field of active flow control. However, the issue of significant premature stall angle of attack in circulation control airfoils is highly prominent. This study numerically simulates the high angle of attack stall process of a circulation control wing using the unsteady Reynolds-averaged Navier-Stokes (U-RANS) turbulent model. A circulation control airfoil is attained by modifying the trailing edge of the NACA-64A-010 airfoil. This modification results in a substantial increase in the lift coefficient, although advancing the stall angle by 5 degrees. A comparative evaluation of aerodynamic characteristics and flow physics differences between the circulation control airfoil and the nonjet airfoil is conducted under poststall conditions. Large-scale long-period fluctuations in aerodynamic forces result from the complex interaction between the trailing edge jet and the vortex system on the leeward side. Effective control of these large fluctuations during stall can be achieved by superimposing a sinusoidal pulsed jet on the steady jet. Activating a sinusoidal pulse jet when the lift coefficient reaches its maximum or minimum value, and matching the excitation frequency with the fundamental frequency of the aerodynamic force fluctuations, yields effective control. This paper unveils the influent of the CC, a kind of active flow control technology, on the airfoil stall characteristics. CC not only dramatically increases the lift coefficient of the airfoil but also leads to significant premature stall angle of attack. The CC airfoil stall is due to the complex interaction between the trailing edge jet and the vortex system on the leeward side. This results in large-scale, long-period fluctuations in aerodynamic forces. However, effective control of these large fluctuations during stall can be achieved by superimposing a sinusoidal pulsed jet on the steady jet under the guidance of this research. It ensures that lift is maintained even at high angles of attack, thus mitigating stall risk. This research promises substantial benefits for the aviation industry, enabling the development of planes that are more fuel-efficient and require shorter runways, while increasing safety. This advancement is expected to have a profound impact on commercial, cargo, and military aviation, leading to cost-effective operations and enhanced flight performance.