A study of eVTOL safety and controllability using Vorcat and HAMSTR CFD

This Phase I proposal will examine the feasibility of using Vorcat’s implementation of a grid-free vortex method coupled with the HAMSTR near-body flow solver to provide accurate simulations of the flow over modern, multirotor, eVTOL vehicles. The combination of these codes will result in a reliable CFD tool with the capability to accurately simulate eVTOL aerodynamics over a large set of flight conditions without resorting to turbulence modeling. When used in the design process, the ability to accurately simulate the correct flow conditions will lead to safer and better controlled eVTOL vehicle resulting in  better design, and will minimization of cost and risk involved in flight tests. It can also be use in the design of realistic flight simulators for pilot training that would further enhancing safety. The project is motivated by the unique capabilities of the Vorcat code in efficiently capturing the physics of complex turbulent flows by using vortical elements to represent the vortices that lie at the heart of turbulent fluid motion.  This (Phases I & II) study will examine the potential benefits gained from coupling the University of Maryland (UMD) HAMSTR technology with the Vorcat technology: the idea is to take advantage of the strengths of both codes – the former applied to near-body flow and the latter to the turbulent flow away from the body – so as to yield a superior computing capability to model the entire flow field. The phase I study will focus on answering several questions that will establish the parameters controlling when and in what way eVTOL aerodynamics can be modeled accurately and effectively. This study will investigate an experimental setting tested at UMD: rotor downwash and its interactions with an offset wing on a helicopter fuselage will be simulated and compared with available experimental data.  The goal is to establish the optimal setup that provides rapid and accurate results that are critical for further, reliable analyses of flight safety, controllability, and other aspects, which can have a major effect on the future of the eVTOL industry. If successful, this project will produce a revolutionary computational methodology that is fast, reliable, and accurate for predicting complex high Reynolds number, turbulent flows associated with advanced, frequently “outside-the-box” eVTOL aerodynamic designs. In Phase II and beyond, the work will focus on pre-selected configurations – possibly of potential customers - that introduce challenging physics, e.g., multi-rotor, moving parts, in proximity to other objects, and free flow settings. Turbulence intensities at various regions will be examined, as well as resolving non-steady interactions of rotor-shed vorticity with other vorticity sources in the flowfield, tracking of wake vortices, etc. It is expected that at the end of Phase I the feasibility of the proposed software technology will be proven and lay the ground work for its validation and verification in Phase II.