Numerical Analysis and Wind Tunnel Validation of Aerodynamic Efficiency with Engine Variations for a Subscale Commercial Aircraft Model

With nacelles, the locations of engines in aircraft can be a significant factor in aerodynamic performance during the aircraft design process, as they are mainly placed on the wing, impacting drag (D) and lift (L). Nacelles, the outer structure of engines, and pylons, which serve as connectors to the wing, are expected to be aerodynamically designed to deliver efficiency and minimize induced drag (D) during flight. While most research on engine-induced effects on performance focuses on the nacelle, the span directional engine locations are often overlooked, and they can be particularly critical for designing new configurations, such as Electric Vertical Take-Off and Landing (eVTOL) and electrified small-scale passenger aircraft. At the same time, the aero-structural aspects are relatively overlooked. Typically, for design and analysis, the aerodynamic performance metrics of aircraft can be estimated using computational methods, such as ANSYS Fluent. However, those computational methods are not fully guaranteed when the aircraft interacts with flow separation, shock waves, and wake that may occur during the flight due to aeropropulsion interactions, especially for new configurations. For performance and design validations, span directional engine locations and their aerodynamic effects are significant in this paper. The authors of this paper investigate aerodynamics using computational methods and wind tunnel testing for validation purposes. Variations are considered, particularly in terms of the wingspan's directional changes, the number, and the size of the engines. When more than a single engine is considered at each wing, proportionally distributed propulsion characteristics, such as size, power, and thrust, have been applied. As an approach to investigating associated aerodynamics, a low-fidelity computational tool based on the lifting-line theory has been selected due to its rapid computational time. Furthermore, corresponding wind tunnel testing has been conducted to validate its results. This study systematically investigates the effects of engine variances along the wingspan using simulation to determine their impact on lift (L), drag (D), and overall aerodynamic efficiency (AE). Then, wind tunnel testing will serve as a validation tool to ensure the accuracy of the simulation results. Findings reveal that engine placement has a significant impact on aerodynamic efficiency (AE), with configurations closer to the fuselage resulting in improved aerodynamic efficiency (AE). For a single engine per wing, an aerodynamic efficiency (AE) of 16.2 was found, which is best when placed near the wing root. The introduction of proportionally distributed propulsion systems featuring smaller engines distributed across the wingspan resolves ground clearance challenges posed by larger nacelles while maintaining acceptable aerodynamic performance. The same trend has been observed; in single engines, the engines closer to the wing roots provide a better aerodynamic efficiency (AE) of 15, 12.84, and 9.75 for 2, 3, and 4 proportionally distributed engines per wing, respectively. The outcome of this work contributes to further study of more efficient aerodynamic designs for enhanced efficiency. As a result, the directional variations of the engines are critical to the aircraft's performance, ensuring that computational and wind tunnel testing results are well-matched.