Evaluating the influence of unsteady air density to the aerodynamic performance of a fixed wing aircraft at different angle of attack using computational fluid dynamics

Abstract

Abstract Recent studies have focused on unsteady aerodynamics of an aircraft using computational fluid dynamics. It was found that a change in the density of air within the flight domain influences the aerodynamic performance of aircrafts in flight. This is as a result of the occurrence of turbulence and unsteadiness in the air velocity vectors. Limited work has focused on the impact of transient change in the density of air to lift, drag and moment coefficient acting on the aircraft fuselage during flight. This paper is aimed at determining how the unsteadiness in the density of air influences the aerodynamic performance of an aircraft with time. To determine the aerodynamic performance of an aircraft within this unsteady airflow condition, lift, drag coefficient and the wing design efficiency was used as the deterministic parameter for the investigation. A compressible simulation was performed for transonic flows with Mach number 0.84. The wing geometry was designed using SOLIDWORKS and the CFD simulation was performed using ANSYS Fluent version 18.1 software. A User Defined Function (UDF) was developed using a MATLAB code. This was aimed at, to introduce a time-dependent change in the density of air, in the Fluent environment. Results obtained showed that a 0.24 average change in air density caused a drop in lift coefficient by an amount 0.01014. The wing design efficiency achieved in this study was 56% and this value is low. Therefore, a change in the density of air will cause the aircraft to observe a poor aerodynamic behavior and eventually stall.