Propeller Noise Prediction using a Vortex Particle-Mesh Method with Immersed Lifting Lines
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The Clean Aviation HE-ART project (Hybrid Electric propulsion system for regional AiRcrafT) aims at demonstrating the viability of a hybrid electric thermal turboprop (e-TP) by running a dedicated integrated ground test demonstrator. This project also includes the study of advanced propeller concepts for improved efficiency and lower acoustic signature. In this framework, medium fidelity tools are particularly attractive in order to be able to quickly assess a large number of design candidates with a sufficient level of accuracy. Such a toolchain to assess the aerodynamic efficiency and the acoustic signature of propellers was developed, based on the hybrid Lagrangian-Eulerian Vortex Particle-Mesh (VPM) method combined with an Immersed Lifting Line (ILL) method in order to compute the propeller aerodynamics. The noise of the propeller is computed using the Ffowcs Williams-Hawkings acoustic analogy expressed for one-dimensional source curves using the compact assumption. The computational efficiency of the VPM-ILL method and its scalability on High-Performance Computing (HPC) infrastructures makes the methodology an ideal medium-fidelity tool for aeroacoustic studies of propellers. First, the noise predictions based on the VPM-ILL method are compared to experimental measurements for a low-Reynolds two-blade propeller at various advance ratios. This demonstrates the capability of the toolchain to predict the tonal noise of propellers. The method is then applied to state-of-the-art propellers for regional transport aircraft. In that case, the lifting line model is constructed from CAD representations of the propeller geometry and the local airfoil aerodynamic properties as a function of the local angle of attack and Mach number are estimated using XFoil. For a baseline propeller geometry, the VPM-ILL aerodynamic and acoustic results are compared to those obtained using geometry-resolved RANS simulations, also performed by Lodz University of Technology during the HE-ART project. A good agreement between both methodologies is found. New propeller concepts are finally assessed using the newly developed toolchain.
