Aerodynamic and Aeroacoustic Analysis of a Ducted Fan with a Variable Nozzle in an Over-the-Wing Configuration

In recent years, hundreds of start-ups have emerged intending to extend urban and regional transport to a new vertical dimension, reducing the time taken to travel between two points and opening the door to countless applications for this new category of aircraft. To date, several e-VTOL architectures have been proposed, most of which employ propellers to generate lift and thrust. However, since the noise generated by these aircraft is a key element, research into propulsion solutions that limit the noise impact is essential. Among the proposed architectures, the most promising seems to be the Duct Electric Vectored Thrust (DEVT) as it would allow not only to reduce the noise produced but also to use the engine itself as a thrust vector system. This thesis, developed in collaboration with the department of Flow Physics and Technology (FPT) at Delft University of Technology, aims to analyze and characterize the effect that a variable nozzle has on the fluid dynamics and aeroacoustics field of an electric ducted fan in an Over-the-Wing (OTW) configuration. The three-dimensional CAD model of the propulsion system used in the analyses was built from an architecture already employed within the department adapted to reproduce the technological solution proposed by the German company Lilium. As a first step, four different configurations with varying duct exit area were analyzed using low-fidelity numerical simulations to determine how nozzle variation affects the engine performance. Based on these analyses, the two most significant configurations were selected for a detailed numerical investigation to illustrate the differences in performance and noise generated by the two configurations. The 3DS PowerFLOW® flow solver was used for the high-fidelity computational analysis. The solver implements the LBM (lattice-Boltzmann) method along with a VLES (Very Large Eddy Simulation) turbulence modelling approach to solve the flow field. On the other hand, far-field acoustic analyses were conducted from data acquired in the fluid dynamics simulations by employing the Ffowcs Williams–Hawkings (FWH) acoustic analogy.