Certain Investigations to Improve the Aerodynamic Performance Parameters of a Surface-Modified Airfoil Structure

Flight vehicles operating in low-speed environments face significant aerodynamic challenges due to weak laminar boundary layers, which lead to early flow separation, reduced lift, and increased pressure drag. Airfoils often experience laminar separation bubbles and abrupt stall, making their performance unstable and difficult to predict. This paper aims to address the low-speed aerodynamic parameter analysis using passive flow control techniques on modified NACA 0021 airfoil profile. The novelty of this research method lies in the integration of dimple-based passive flow control structures on the upper surface of a NACA 0021 airfoil specifically designed to delay flow separation and enhance low-speed aerodynamic performance. Unlike most previous studies that focus on conventional vortex generators or active flow control methods, this work uniquely demonstrates that strategically dimple on the airfoil surface modifications significantly improves the lift characteristics. The methodology begins with the design of baseline or non-modified airfoil and the surface-modified NACA 0021 airfoils, subjected to aerodynamic analysis for the varying angle of attack (α) at low-speed environment. The upper surface of the baseline airfoil is designed with spanwise dimple regions to construct the surface-modified structure to study the aerodynamic performance. By combining 3D-printed experimental testing and numerical flow separation analysis for the varying angle of attack (α) at the operating speed of 20 m/s, the study provides one of the first comprehensive evaluations showing that a surface-modified NACA 0021 airfoil achieved a notable increase in aerodynamic performance compared to the baseline airfoil. In addition, the research evident the delayed flow separation behavior for surface-modified NACA 0021 airfoil over the non-modified structure through numerical simulation process. the comparative results of experimental and numerical simulation concluded that the surface-modified NACA 0021 airfoil effectively performed over baseline NACA 0021 airfoil and arrived the maximum coefficient of lift (C_l) = 1.86 at 12.5° angle of attack (α). Eventually, this paper suggested a novel passive technique with improved aerodynamic coefficients for the low-speed operable airfoils.