Abstract
Large Eddy Simulation (LES) is performed using the NASA Source Diagnostic Test database at approach conditions (62% of the design speed). The simulation is performed in a periodic domain containing one single blade. The aerodynamic and acoustic results are compared with the experiment. Ffowcs Williams and Hawkings’ (FWH) analogy is used to compute the far-field noise from the solid surface of the rotor blade. The analogy is computed for the full blade and for its tip region to see the contribution of the latter. The dynamic mode decomposition is performed at different iso-radii of the computational domain. The contribution of the tip region to the far-field noise is observed around the first blade passing frequency (2.8 kHz) and 4 kHz due to the mixing process of the leading-edge and tip vortices. The rest of the blade contributes more at frequencies above 7 kHz which corresponds to the trailing-edge noise. The high-amplitude modes are observed at 75% and 90% of the spanwise length. These modes contribute to the corresponding frequency humps in the far-field spectrum.
Highlights
The latest noise standards imposed by International Civil Aviation Organization (ICAO) [1] have further restricted the maximum noise level for an aircraft certified after 2018
The hybrid Lattice–Boltzmann Method (LBM)–Very Large Eddy Simulation (VLES) [13,14] and the hybrid unsteady Reynolds-Averaged Navier–Stokes–LES [15,16] computations give a reliable prediction of the rotor–stator interaction (RSI) noise, as it may not require such a high grid resolution around the rotor blades
The results show that the wake width is well captured in LES
Summary
The latest noise standards imposed by International Civil Aviation Organization (ICAO) [1] have further restricted the maximum noise level for an aircraft certified after 2018. The rotor–stator interaction noise is generated by the interaction between the turbulent wakes of the rotor and the outlet guide vanes (OGV) This is currently the most studied noise source as the rotor wakes can be well resolved by using various numerical methods. The hybrid Lattice–Boltzmann Method (LBM)–Very Large Eddy Simulation (VLES) [13,14] and the hybrid unsteady Reynolds-Averaged Navier–Stokes (uRANS)–LES [15,16] computations give a reliable prediction of the RSI noise, as it may not require such a high grid resolution around the rotor blades. The previous studies showed that the modeling of the trailing-edge and turbulence-interaction noise sources is not enough to correctly predict the total rotor broadband noise spectrum [17,18]. The current study aims at providing a deeper understanding of these noise sources and their contribution to the overall rotor broadband noise.
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