An important consideration in the design and operation of aircraft, racing cars, and other vehicles is the aerodynamic performance of airfoils. Airfoil shape, angle of attack, and Reynolds number are some of the variables that affect the lift and drag forces produced by an airfoil.

The rotating cylinder is a flow control method used to manipulate the behavior of fluid flows, often to improve aerodynamic performance, reduce drag, enhance lift, or delay flow separation. These methods are employed in various engineering applications, including aerospace, automotive, and marine industries. The rotating cylinders can improve the performance of an airfoil through the Magnus effect by generating lift forces around the rotating body when placed in the cross-flow of a fluid. The direction and speed of rotation can affect the aerodynamic performance of the airfoil. By creating a vortex field rotating cylinders can delay flow separation and increase lift. This effect has been studied experimentally and numerically, and the results have shown that the rotating cylinder can significantly improve the performance of airfoils at high angles of attack.

The position and diameter of the rotating cylinder can also affect the aerodynamic performance of an airfoil. In general, the closer the rotating cylinder is to the airfoil, the greater the performance improvement. However, the optimal position of the rotating cylinder depends on many factors, such as the shape of the airfoil, and the angle of attack.

The primary aim of this study is to investigate the effect of the position and diameter of the rotating cylinder on the aerodynamic performance of NACA 23015 Airfoil. The study has been conducted using computational fluid dynamics (CFD) simulations. This research endeavor aims to contribute to understanding the rotating cylinder effect as a flow control technique for airfoil aerodynamics. The findings from this study could potentially provide valuable insights into novel ways of improving aerodynamic performance, reducing drag, and enhancing stall characteristics in various engineering applications, particularly in aircraft design and optimization.

The possibility of enhancing airfoil and aircraft performance has been extensively studied in the literature using both computational and experimental techniques. The paper introduces a method for decomposing flow near a moving boundary, enabling analysis of complex flow fields with moving boundaries. This is useful in aircraft, wind turbine, and underwater vehicle design, providing insights into flow-induced pitch oscillations and optimizing airfoil design for better performance and efficiency. The method's applicability is uncertain due to the assumption of known boundary motion [1]. Researchers have claimed that the Magnus effect can produce much higher lift forces compared to other lift-generation devices, such as airfoils, given the same projection area and inflow velocity [2]. A study on the Magnus effect on a circulation control airfoil (CCA) found that increasing the cylinder's rotational speed in a clockwise direction improved the airfoil's aerodynamic performance, while counterclockwise rotation produced opposite effects [3]. V.J. Modi et al's 1998 study found that judicious selection of momentum injection and cylinder surface geometry can improve lift coefficient and stall angle delay in wind tunnel testing, with a momentum injection ratio of UC/U = 4 [4]. Ahmed Z. Al-Garni et al's study found that a leading-edge rotating cylinder increases the sectional lift coefficient and lift-to-drag ratio at low angles of attack, reducing the need for higher angles. High-speed rotation delays stall by 92 and 160%, respectively. This makes the airfoil more maneuverable and improves STOL performance [5]. X.Du et al.'s 2002 study found that leading-edge cylinder rotation affects the boundary layer, wake, and lift-to-drag ratio in a NACA 0015 airfoil. They found that boundary-layer momentum thickness decreases with rotation [6]. The thesis aims to enhance airfoil aerodynamic performance by controlling the boundary layer with a rotating cylinder at the leading edge. The objectives include increasing lift and lift-to-drag ratio, delaying flow separation, and achieving a higher stall angle of attack. The research uses experimental and numerical studies on a NACA0024 airfoil, resulting in a 48% increase in maximum lift coefficient and stall angle of attack, and a 47% increase in maximum drag coefficient [7]. A rotating cylinder was analyzed using ANSYS FLUENT software, using a mesh of 94,000 elements and a k-ε model. Results closely matched experimental data at a 5° angle of attack and cylinder-to-free-stream ratios of 0 and 1. Further research could explore multiple parameters and their impact on aerodynamic performance [8]. The paper explores boundary-layer control techniques and their effectiveness in improving the aerodynamic performance of airfoils. It focuses on a flow-control technique involving integrating a rotating cylinder onto an NACA 4418 airfoil. The study found that a rotating cylinder near the separation point of the airfoil improves the lift coefficient by 7–12% under a 4° angle of attack, with separation suppression at moderate and post-stall angles. The maximum increment of lift coefficient alters from 86 to 125% under a 4° angle of attack, and the stall angle increases over 5° [9]. The use of a leading-edge rotating cylinder in an asymmetric airfoil can increase efficiency by 24% and delay stall angle by 20% for lower velocity ratios. This concept, dating back to the mid-19th century, has been studied using techniques like blowing and suction. A modified NACA 23018 airfoil [2] showed a higher maximum lift coefficient and increased drag coefficient, but performance degraded at zero-velocity ratios [10]. For high-altitude platform applications, the paper suggests a twin rotating cylinder embedded on a Selig S1223 airfoil and flat plate. When fluid flow analysis was simulated using computational fluid dynamics, the lift coefficient and stall angle delay for changed models saw considerable improvements. A new infrastructure called the High-Altitude Platform (HAP) was created to remedy the flaws in terrestrial and satellite communication networks. ANSYS WORKBENCH 2019 software was used to test the cylinder's aerodynamic performance, and the results showed considerable improvements in lift coefficient and stall angle delay. The Magnus effect was successfully applied to the model, as evidenced by an increase in lift coefficient, a decrease in CD, and an extension of stall angle delay after the momentum injection [11]. The study investigates the use of a NACA0012 airfoil with pitching oscillation to control vortex shedding and reduce drag on a cylinder, potentially benefiting engineering applications in launch vehicles, ship masts, and submarine pipelines [12].

Although there are numerous researches on the effect of rotating cylinders on airfoils, there is a lack of studies on the effect of cylinder diameter and position on the NACA 23015 airfoil. Especially there is a lack of distinct studies regarding this effect on asymmetric airfoils. Our study focuses on the effect of a rotating cylinder on this airfoil by placing it at different positions along the chord length of the airfoil and also changing the diameter of the cylinder. This study can contribute to the existing study on the use of active flow control methods like rotating cylinders in improving the aerodynamic performance of the NACA 23015 airfoil.