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Development of computational and experimental noise assessment and suppression methodologies for the next generation of silent distributed propulsion configurations

Periodic Reporting for period 1 - SilentProp (Development of computational and experimental noise assessment and suppression methodologies for the next generation of silent distributed propulsion configurations)

Reporting period: 2020-04-01 to 2021-06-30

SilentProp will advance the understanding of key noise aspects involved in Distributed Electric Propulsion (DEP) configurations, at experimental and numerical levels and demonstrate these at TRL4. It is directly contributing to the thematic topics of the CleanSky 2 JU workplan.

It will also evaluate experimentally and numerically noise suppression and shielding effectiveness for popular employed technologies, as well as suggest and assess new ones. This will enable initial evaluation of the overall noise level achievable for typical DEP options, as well as provide substantiated appraisal of the efficiency of several noise mitigation means including propeller phasing, acoustic liner treatments and serrated wing geometries.

WP 1 - Experimental studies on noise emitted from DEP configurations
• Devise and deliver a multi-purpose experimental DEP configuration for extensive noise measurements.
• SilentProp will deliver computational results for a minimum of 500 case studies.
• Provide insight into the underlying physics of noise generation from multi-propeller configurations and extensively assess the aeroacoustics of propeller-propeller and propeller-wing interactions for“leading-edge” and “trailing-edge mounted” DEP configurations.
• SilentProp will deliver results on a minimum of 50 different cases, specifically focusing on investigating propeller-propeller and propeller-wing interactions.
• Examine opportunities for directional noise control, notably through propeller phase locking effects.
SilentProp will deliver results on a minimum of 40 different cases, specifically focusing on investigating propeller phase locking effects. Directional noise reduction at the order of 5dB is expected.

WP 2 - Numerical modelling of near-field and far-field noise generated by a DEP system
• Establish a reduced order surrogate model for the fast prediction of noise generated by a DEP system and extrapolate experimental results towards a DEP configuration including a greater number (more than 3) and/or larger propellers. Also, identify essential fluid dynamics in flow around a DEP system through high fidelity Large Eddy Simulation (LES).
• SilentProp will deliver results on a minimum of 150 different numerical DEP cases, to investigate noise reduction potential solutions. Noise reduction at the order of 10-15dB is expected for the elaborated designs.

WP3 - Noise suppression and shielding technologies
• Experimentally and numerically verify the effectiveness of passive, adaptive and metamaterial liner and serration treatments for DEP.
• SilentProp will deliver results on a minimum of 7 different cases, specifically focusing on investigating liner treatments for noise reduction purposes. Far field noise reduction at the order of 7-15dB is expected.
WP1 - Experimental Studies of Noise from DEP configurations - The isolate propeller test rig is designed and manufactured. Aerodynamic and aero-acoustic measurements are carried out. A range of propellers is selected with different diameters, pitches, and the number of blades. Propellers are designed and manufactured in the Mejzlik, and all propellers are delivered to the UoB. The leading edge mounted DEP test rig is designed and manufactured. The schematic is included. The testing of the DEP rig is working in progress. Different parametric studies are carried with different diameters, P/D ratios, number of blades, incoming flow velocities, and turbulent intensities.

WP2 - Numerical modelling of near-field and far-field noise generated by a DEP system - Solver methodology has been recognized and is being developed. Reduced order modelling has been started, however delays in its completion are expected. High fidelity simulations has been started by selecting a 9" propeller.

WP 3 - Noise shielding and suppression technologies - the literature review and the accompanying roadmap task has been completed. Over 30 different porous materials have been designed, fabricated and tested at UoB. Some of the treatments have shown promising results.

WP4 - Project Management control and correction of COVID delays are ongoing.
SilentProp will provide valuable data underpinning noise assessment for future DEP systems and is directly contributing to the thematic topics of the CleanSky 2 JU workplan. The breakthrough concept and technology demonstration proposed by SilentProp will have a wide range of impacts ranging from those listed in the CS2JU work programme to the ACARE objectives that lead to wider economic, social and environmental impacts. The uniqueness of the current situation means that there are no real benchmarks that can currently be assessed against as there are limited publications, especially on noise interaction between multiple propeller systems.
Example Propeller 2
Aeroacoustic Facility with Test Rig
Example Propeller 1
5 Bladed Propeller installed on Rig