Various aspects of the numerical modeling of a scale-model turbofan blade are investigated for the purpose of future noise assessment. The fan geometry considered is the baseline configuration of the "Fan Noise Source Diagnostic Test" (SDT) experimental setup. Both Reynolds Averaged Navier-Stokes (RANS) simulations and Large Eddy Simulations (LES) are performed for a single rotor blade without the stator vanes and compared against the full configuration from previous works. With RANS simulations the mesh convergence is systematically studied. In the LES, two wall models and two numerical schemes are considered to evaluate the sensitivity of the boundary-layer transition to turbulence on the blade suction side. The different LES results are compared with the RANS solutions obtained using fully turbulent and transitional turbulence models. All RANS results show similar performance, whereas in the LES the no-slip wall condition gives better performance than the log-law slip wall condition. The prism layers on the hub and the shroud change the boundary layer profile upstream of the blade but do not affect the performance. On the blade, the RANS simulations show a laminar recirculation bubble whereas the LES exhibit a leading-edge vortex spiralling radially. The transitional RANS turbulence model gives the best agreement with the LES on the pressure side. The LES results are more affected by the mesh resolution than by the wall model or the numerical scheme, especially in the tip. In the wake all results show a good agreement with the experiment. Nomenclature Variables y + Dimensionless wall distance τ w Wall shear stress C p = P−P ∞ 0.5ρ ∞ U 2 ∞ Mean pressure coefficient C f = τ w 0.5ρU ∞ Mean skin friction coefficient U Mean velocity P Mean pressure Indices w Wall quantity ∞ Free-flow quantity t Total (stagnation) quantity This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License CC-BY-NC-ND 4.0

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Large Eddy Simulation is performed using the NASA Source Diagnostic Test turbofan at approach conditions (62% of the design speed). The simulation is performed in a periodic domain containing one fan blade (rotor-alone configuration). The aerodynamic and acoustic results are compared with experimental data. The dilatation field and the dynamic mode decomposition (DMD) are employed to reveal the noise sources around the rotor. The trailing-edge radiation is effective starting from 50% of span. The strongest DMD modes come from the tip region. Two major noise contributors are shown, the first being the tip noise and the second being the trailing-edge noise. The Ffowcs Williams and Hawkings’ (FWH) analogy is used to compute the far-field noise from the solid surface of the blade. The analogy is computed for the full blade, for its tip region (outer 20% of span) and for lower 80% of span to see the contribution of the latter. The acoustics spectrum below 6 kHz is dominated by the tip part (tip noise), whereas the rest of the blade (trailing-edge noise) contributes more beyond that frequency.

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