Assessment of Rapid Modeling Tools for Unmanned eVTOL Proprotor Design Appliations

High-performance rotor plays a vital role in viable eVTOL operation. While a simple design approach such as the combined blade element and momentum theory are adequate for the initial sizing of the rotors, they are not sufficiently accurate for estimating the hover and forward flight performance. There is a need for well-validated rapid modeling tools with a required accuracy. Therefore, this study compares the performance of two open-source simulation tools, XROTOR and FlowUnsteady. XROTOR is a specialized solver developed for analyzing rotor blades and wind turbines based on Lifting Line Theory, and it provides results quickly. FlowUnsteady is an open-source computational framework based on the reformulated vortex particle method (rVPM). The comparison results reveal that XROTOR thrust and power are higher than FlowUnsteady. This difference arises because XROTOR, using Lifting Line Theory, performs 2D calculations and ignores some aerodynamic drags. In contrast, FlowUnsteady utilizes the rVPM method, offering a more accurate assessment of aerodynamic drag by discretizing the Navier-Stokes equations with particles. XROTOR can compute results much faster than FlowUnsteady but XROTOR report overestimates Thrust and power due to its inability to capture 3-D effect of rotor flows correctly.