Validating Flow360 to Predict Noise from Joby’s Five-Bladed eVTOL Propeller

What is it about?

This study, explores how well a computational tool called Flow360 can predict noise generated by Joby Aviation’s full-scale, five-bladed electric vertical takeoff and landing (eVTOL) propeller. eVTOL aircraft represent a new and rapidly developing category of urban air vehicles. Because these aircraft operate in cities, noise pollution is a major concern for public acceptance and regulatory approval. Traditional helicopter noise models do not accurately capture the unique noise characteristics of eVTOL propellers, which have different designs featuring multiple, slower-turning blades. The research team used high-fidelity numerical simulations, specifically Delayed Detached-Eddy Simulations (DDES), combined with a Ffowcs Williams–Hawkings (FW–H) acoustic analogy, to predict both tonal (consistent frequencies related to blade passing) and broadband (turbulence-driven) noise components from the propeller. To validate these predictions, they compared their results against measurements collected at NASA’s National Full-Scale Aerodynamics Complex (NFAC) during tests of the propeller in hover and pure edgewise flight (where the propeller moves forward). Key to the analysis was the use of the Vold–Kalman order-tracking filter (VKF) to separate tonal noise from broadband noise, enabling detailed comparisons of different blade pitch angles and flight conditions. The researchers also performed source-noise analyses to identify which parts of the propeller’s surface contributed most to noise generation, revealing underlying flow mechanisms such as the roll-up of tip vortices and crossflow-induced separations. The results showed that Flow360 accurately reproduced thrust, torque, blade-passing frequency harmonics, broadband spectral levels, and noise directivities across different pitch settings and flight modes. This demonstrates that Flow360 is a capable tool to simulate full-scale eVTOL propeller noise for various flight conditions. To organize the findings, the team proposed an ‘opportunity pathways’ framework (conceptually inspired by existing models) to guide how integrated computational and experimental aeroacoustic studies can better support design optimization and community noise assessment for eVTOL vehicles.

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Photo by Hyundai Motor Group on Unsplash

Photo by Hyundai Motor Group on Unsplash

Why is it important?

As eVTOL aircraft become closer to widespread adoption, the challenge of managing and reducing their noise footprint in populated areas grows more urgent. Unlike traditional helicopters, eVTOL designs often use multiple propellers with slower blade speeds and complex airflow interactions, creating noise signatures that are not well understood or predicted using legacy models. Inaccurate noise prediction can lead to poor design choices or community resistance, slowing down the deployment of these new aircraft. By validating Flow360's capability to reliably predict the tonal and broadband noise of complex, full-scale eVTOL propellers, this study provides a valuable tool for engineers designing quieter vehicles. Understanding the specific flow phenomena behind noise generation enables targeted design modifications and informs noise mitigation strategies. Moreover, the research emphasizes the importance of coupling advanced simulations with experimental data in realistic testing environments like NASA’s NFAC. This combined approach builds confidence in predictions across different flight regimes (hover, transition, edgewise flight), critical for certifying eVTOLs and improving their public acceptance. Ultimately, this work supports the broader goals of urban air mobility, helping to integrate new flight technologies into cities with minimal disturbance. Accurate aeroacoustic prediction tools like Flow360 will be essential to meeting regulatory noise limits and achieving sustainable, community-friendly eVTOL operations in the near future. Key takeaways: 1. Flow360, using high-fidelity computational fluid dynamics and aeroacoustic models, accurately simulates both tonal and broadband noise from Joby’s five-bladed eVTOL propeller. 2. Validation against full-scale measurements from NASA’s NFAC shows strong agreement in thrust, torque, noise frequencies, spectral levels, and directional noise patterns in hover and edgewise flight modes. 3. Advanced filtering techniques enable clear separation of tonal noise (linked to blade passing) from broadband noise (due to turbulence), deepening understanding of noise sources. 4. Noise arises from multiple aerodynamic phenomena including tip-vortex roll-up in hover and flow separation in forward flight, informing targeted noise mitigation approaches. 5. This study establishes a validated CFD-CAA framework to support quieter eVTOL propeller designs and improved community noise engagement as urban air mobility advances.