Investigating the impact of velocity fluctuations and compressibility to aerodynamic efficiency of a fixed-wing aircraft

Abstract

Steady airflow over the wing of an aircraft in-flight is critical to achieving maximum aerodynamic performance. However, commercial flight routes are most times characterized by fluctuations in the airflow properties. The unsteadiness in the air velocity vectors and mass flow directly affects the aerodynamic efficiency (AE) of the aircraft during flight and could lead to air accidents. These correlations between the variation in the airflow properties and the aerodynamic coefficients of a fixed-wing aircraft are not yet fully established. Therefore, this paper makes use of computational fluid dynamics code to study the link between these functions. Herein, a realistic wing model of the BOEING 737 aircraft was used for the investigation. Simulations were carried out at a Mach number of 0.84, with the nonzonal Hybrid RANS-LES method. The fluctuations in the airflow properties were modeled using the vortex fluctuation algorithm (vortex method) in Fluent software. The vortex number ,N formed in the flow field were varied in the range of 100–300. Findings from the numerical study revealed that the wing achieved an optimal AE of 95.1% for the steady case scenario. However, the wing’s AE was significantly reduced by 30% when the streamlined velocity was perturbed by the fluctuating velocity component of the flow. Also, a further decrease in the wing performance was observed with an increase in the divergence of the airflow velocity vectors which experienced a stalling effect after an 80 s flow period forN=300. Moreover, a static increase in the density of the airflow from 1.255 kg/m3 (15 °C) to 1.455 kg/m3 (−10 °C) contributed to approximately a 20% reduction in the lift and moment coefficients for N=300.

Keywords

• Airflow instability
• BOEING 737-800 aircraft
• Hybrid RANS-LES
• Wing performance
• Unsteady aerodynamics