Studying the Aerodynamics of Multi-Rotor Drones

Overview

Recent interest in technologies that will decrease emissions and fuel burn has led to research in aircraft employing hybrid or full electric propulsion systems. A multirotor lift design is frequently used for small electric rotorcraft partly due to the mechanical simplicity of both the rotor hub and the controls. The use of multiple rotors provides redundancy as well as cost efficiency, as the cost of multiple simple rotors is lower than that of a single complex rotor. However, unlike most helicopters with single main rotor, the interactions between multiple rotors and a vehicle's fuselage present a number of unique challenges, and are important factors to consider in the design of multirotor aircraft.

Project Details

High-fidelity computational simulation tools are required to investigate the complex physics of multirotor interactions, which are not well understood at this time. For applications in civil operations, such as recreational use, cargo delivery, or even human transportation, it is necessary to assess aerodynamic performance and noise levels caused by the rotors. The current work being done at NASA's Ames Research Center covers not only small-scale drones (less than a few feet in length or width) but also large-scale multirotor vehicles for heavy-lifting applications.

Results and Impact

Computational simulations of rotorcraft designs were performed using thousands of cores on the Pleiades supercomputer at the NASA Advanced Supercomputing (NAS) facility to analyze airflow interactions between multiple rotors, wings, and the vehicle fuselage.

• New conceptual designs of large drones were investigated during this study, including a dual-winged quadcopter and a tandem coaxial rotorcraft (a helicopter with two sets of coaxial rotor assemblies, which are mounted at the front and back of the vehicle).
• Various hybrid turbulence models, including detached eddy simulations, were assessed for interactional aerodynamics.

The computational results of this work show that quadrotors can be scaled up in size without sacrificing performance. If large quadrotors are shown to be as efficient as small drones without increasing noise, vertical-lift multirotor vehicles may become the new paradigm for helicopter designs for the future of human and cargo transportation, delivery systems, surveillance, and disaster relief.

Why HPC Matters

Access to the Pleiades supercomputer has been essential for the work done for this project. Visualizations of these high-fidelity simulations, developed by the visualization team at NAS, have been critically important to understanding the complex, unsteady, turbulent flow interactions. Our team used tens of millions of processor hours to complete this work.