Aerodynamic optimization of eVTOL rotor profiles

Abstract

Electric Vertical Take-Off and Landing (eVTOL) aircraft are currently being developed to fill a gap in the air transportation sector and, simultaneously, provide zero-emissions alternatives to current generation carbon-intensive short-haul aircraft. However, unlike conventional fixed-wing or rotary aircraft, eVTOL rotors operate in both hover and forward flight configurations. This significantly increases the range of operating conditions experienced by the rotor, introducing multiple aerodynamic design challenges. Additionally, the efficiency of these rotors is particularly important, since it has a direct impact on power draw and aircraft range. In this presentation, a classical airfoil, the ClarkY, is used as a baseline configuration for an eVTOL rotor section. A gradient-based optimization framework using an adjoint solver in Discrete Adjoint with OpenFOAM (DAFoam) with the Reynolds Averaged Navier-Stokes (RANS) approach is then used. In this study, a control point-based free form deformation (FFD) method is used in the framework in order to change the aerodynamic shape. The objective function for this optimization is the lift-to-drag ratio, with additional target lift and geometric constraints. The baseline design is first validated against experimental data, and then the optimization is completed for several target lift coefficient values. Results demonstrate that the lift-to-drag ratio can be increased significantly while maintaining the desired target lift coefficient. Preliminary results for complete rotor optimization using RANS will then be presented, followed by preliminary airfoil optimization using Large Eddy Simulation (LES).