B a c kg r o u n d
Aerospace
NLR takes the controls to bring propeller noise down As the number of aircraft continues to increase, noise is becoming a headache. As part of a public-private collaboration known as the Taste project, aviation propeller manufacturer Dowty is turning to NLR and its in-house developed technologies to precisely measure, and ultimately mitigate the noise at the source. Collin Arocho
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ith drones of all sizes, personal air transport and smaller planes increasingly filling the sky, propellers will be a mainstay of sky-bound transportation. This comes with its own set of challenges – specifically in the aviation industry. One challenge coming to light is the noise generated by the open blades of these aircraft flying at lower altitudes. As a propeller rotates, it creates thrust due to the forces on its blades. This rotation also results in an acoustic field that’s perceived, particularly in the far field (at a distance from the source), as noise. The level of the disturbance directly correlates with the amount of force on, and the subsequent speed of, the turning blade and is seen as a growing nuisance, for both people
Taste
Within the Techniques for Acoustic Measurements in High-Speed Test Environments (Taste) project, the Royal Netherlands Aerospace Centre (NLR) is looking into possible methods to accurately measure and mitigate the noise produced by propeller-driven aircraft. Partners include UK-based Dowty Propellers and NLR’s sister organization GermanDutch Wind Tunnels (DNW). NLR participation is co-funded by Holland High Tech, Top Sector HTSM, with a public-private partnership grant for research and innovation.
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Credit: NLR
on the ground, as well as those in the sky. Enter the British engineering company Dowty Propellers.
Taste
The UK-based aerospace experts, which specializes in the design and manufacturing of integrated propeller systems, wanted to investigate if these sound issues could be mitigated by identifying the sources. But before Dowty could set a hard goal of reducing noise, they first needed to determine if it was possible to get more accurate acoustic measurements. To do this, the British engineering company initiated a study, called Techniques for Acoustic Measurements in High-Speed Test Environments (Taste), and reached across the North Sea to the Royal
Netherlands Aerospace Centre (NLR) for assistance in the project. In this collaboration, Dowty would provide its knowledge and expertise on propellers and rely on NLR’s experience in algorithm development and industrial testing, before finally turning to the low-speed wind tunnel facilities of NLR’s sister institute German-Dutch Wind Tunnels (DNW), the third arm of this public-private alliance. “Essentially, Dowty turned to us to see if we could get more accurate acoustic measurements from the propellers in a highspeed environment, which is certainly not a trivial task,” describes Marthijn Tuinstra, a principal scientist at NLR. “To achieve this, though, we’ll need to advance the state-ofthe-art in measuring techniques.”
