Numerical Investigation and Aerodynamic Configuration Optimisation of a VTOL Flying Wing UAV

Abstract

The manuscript presents the results of the computational investigation into the aerodynamic characteristics of a Vertical Take-Off and Landing (VTOL) flying wing unmanned aerial vehicle (UAV), with particular emphasis on the aerodynamic behaviour of the lifting surface. The airflow around the model is analysed over a wide range of velocities corresponding to Reynolds numbers Re≈9.66×10⁴ – 1.29×10⁶. Special attention is devoted to the influence of the angle of attack (AOA), airflow regimes, and wing geometric parameters on the aerodynamic efficiency and stability of the aircraft.

The following tasks have been achieved in this study: the development of the geometric and computational wing model; generation of the computational domain and mesh with verification of the grid convergence; computational modelling of the flow at different velocities and AOA; determination of aerodynamic coefficients; construction of the aerodynamic polar; evaluation of aerodynamic and energy efficiency; and analysis of stability and transition regimes, including the influence of ground effect.

The study is based on the numerical solution of the unsteady Reynolds-averaged Navier-Stokes equations using the Low Reynolds k-ε turbulence model. The finite volume method has been applied for discretization. The simulations have been carried out in the SolidWorks/FlowEFD software environment using adaptive computational mesh and variable time step. The reliability of the results has been confirmed through the grid independence analysis.

It has been found that within the AOA range α = -4° – 14°, the lift coefficient dependence C _L (α) remains linear, while the drag coefficient C _D (α) follows the quadratic trend. The maximum aerodynamic efficiency reaches K≈11 at AOA of α≈6°, corresponding to the optimal cruise flight regime. It has also been shown that the influence of the Reynolds number on the aerodynamic characteristics within the investigated range is insignificant. The static longitudinal stability of the aircraft has been confirmed by the negative slope of the pitching moment dependence. The characteristics of the VTOL transition regime have been determined, and a significant influence of the ground effect has been identified, leading to the increase in lift and the reduction in induced drag at low flight altitudes.

The results of the study confirm the high aerodynamic efficiency of the flying wing configuration for VTOL UAVs. The optimal flight parameters and transition conditions providing maximum aerodynamic and energy efficiency have been determined. The obtained dependencies and identified patterns can be applied during the design, optimisation, and development of the control systems for UAVs of this type.

The obtained results can be used not only for analysis purposes, but also as an engineering tool for the development of aerodynamically efficient UAV configurations at the early design stage, making it possible to reduce the need for experimental testing and shorten the flying vehicle development cycle.