Development of a Low Noise Drone Propeller Using CFD Simulations

Abstract

Noise pollution generated by drones has in recent years become a concern for humans and wildlife and has in some regions resulted in regulatory backlash. This thesis investigates the possibilities of developing a low noise drone propeller using computational fluid dynamics (CFD) simulations. A commercial drone propeller from the manufacturer APC Propeller has been modified with different forms of serrations to the trailing edge of the propeller. The simulations, conducted in the open source program OpenFOAM, using an LES turbulence model and an aeroacoustic analogy, shows promising results. The modified propellers shows an overall decreased sound pressure level compared to the unmodified propeller. However, the simulations do have some limitations and only covers a limited amount of working drone scenarios. Furthermore the modifications that are evaluated are only done to the trailing edge of the propeller. Overall the study shows promising results in using CFD to develop a low noise drone propeller. Future work could include modifications to the propeller in other locations than the trailing edge, and in a more varied set of working scenarios.

Popular Abstract

Noise from drone propellers presents a challenge to the adaption of drones. What if the drone propellers can be made quieter by combing millions of years of evolution, with modern computer tools such as Computational Fluid Dynamics?

Imagine a future where your pizza is delivered – still piping hot – in a few minutes, straight out of the sky! With drones, this future is possible. The problem today is that drones are noisy and a sky full of them would turn our cities’ soundscapes into buzzing cacophonies. Studies have shown that the high-pitched noise that drones emit is more annoying than that of any ground vehicle, and that the noise comes mainly from the propellers. But what if the propellers can be modified to be less noisy? That is the study of this thesis.


Using Computational Fluid Dynamics (CFD, a powerful technique for simulating fluid flows and acoustics), simulations have been run on a modified drone propeller from the company APC Propellers, to see if it can be made to emit less noise. The modifications that have been made are inspired by nature. Certain owls – barred and barn owls – manages to fly almost silently, and what scientists believe is the cause of this is certain fringes on the owl’s wings. When a wing glides through the air, there are vortices – or turbulence – in the air behind the wing. These vortices generates sound, and the larger the vortex the louder the sound. The fringes on the owl’s wings effectively breaks down the vortices and therefore helps minimising the sound.
Using modern CAD software, a computer prototype of the APC propeller is created. This model is then used for computer simulations with CFD. The simulations evaluate the propellers performance during flight and how much vortices – and thereby noise – that is created.
The simulations shows that the serrations to the drone propellers successfully work the same way as the serrations found on the wings of owls – the vortices generated are broken down faster and the overall sound level is reduced. Looking to nature for inspiration seems to be a winning concept, and creating a low noise propeller using CFD is indeed possible. For further improvements, future work could include modifications in other forms than just serrations to the trailing edge of the propeller.

• author: Schulz, Axel
• supervisor: Robert-Zoltán Szász
• organization: Department of Energy Sciences
• course: MVKM01 20221
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Drone Propeller Low Noise Computational Fluid Dynamics CFD
• report number: LUTMDN/TMHP-23/5526-SE
• ISSN: 0282-1990
• language: English
• id: 9131449
• date added to LUP: 2023-07-04 09:54:46
• date last changed: 2023-07-04 09:54:46