Aeroacoustic Assessment of Leading Edge Bumps in Industrial Fans by Means of Hybrid LES/RANS

C2 - Numerical Methods

Numerical computations of industrial turbomachinery usually rely on high-Reynolds RANS approach for design and verification. Low-Reynolds RANS and URANS are usually adopted for analysis purposes. In recent years hybrid LES/RANS has became a vialable approach following the constant reduction of computational costs and increase of availability of massively parallel hardware (Corsini et al., 2013). Key issues for hybrid LES/RANS methodology are i) numerical robustness and ii) accuracy. These aspects can be respectively related to the blending of LES and RANS and the capability of the baseline RANS model to correctly predict the characteristics of the turbulent flow. For this reasons here we focus on the application of a hybrid LES/RANS methodology based on an elliptic relaxation model (Delibra et al., 2010) that was found to be numerically robust and able to correctly internal flows in turbomachinery.
Here this methodology is applied to the prediction of noise emissions from a tunnel and metro fan blade for high temperature applications with a modified leading edge (Corsini et al., 2014). This methodology is applied in order to reconstruct the pressure and velocity fluctuations of the large-scales of motions in order to acquire information on the acoustic performance of the modified leading edge with respect to the datum (straight) configuration.

[1] A. Corsini, G. Delibra, and A. G. Sheard, A Critical Review of Computational Methods and Their Application in Industrial Fan Design, ISRN Mechanical Engineering, vol. 2013, Article ID 625175, 20 pages, 2013
[2] A. Corsini, G. Delibra and A. G. Sheard, The application of sinusoidal blade-leading edges in a fan-design methodology to improve stall resistance, Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy May 2014 228: 255-271.
[3] G. Delibra, K. Hanjalić, D. Borello, F. Rispoli, Vortex structures and heat transfer in a wall-bounded pin matrix: LES with a RANS wall-treatment, International Journal of Heat and Fluid Flow, Volume 31, Issue 5, October 2010, Pages 740-753.