Bio-Inspired Blade Cascades: Numerical Predictions Versus Experimental Measurements

Area of Science:

• Aeroacoustics
• Computational Fluid Dynamics (CFD)
• Bio-inspired Engineering

Background:

• Leading edge serrations are used to reduce noise in blade cascades.
• Accurate prediction of broadband noise from turbulent flow is challenging.
• Numerical simulations require validation against experimental data.

Purpose of the Study:

• To numerically and experimentally validate aeroacoustic predictions for bio-inspired serrated blade cascades.
• To assess the performance of various turbulence models in capturing broadband noise.
• To analyze the impact of serrations on turbulent flow coherence.

Main Methods:

• Transient simulations of a four-blade cascade using Spalart-Allmaras (SA), k-ω SST, k-ε, Scale-Adaptive Simulation (SAS), and Large Eddy Simulation (LES) models.
• Testing multiple timestep resolutions for temporal accuracy.
• Experimental measurements of acoustic spectra and blade surface pressure.

Main Results:

• Turbulent jet-blade interaction noise (0.9-5 kHz) was captured by simulations.
• SAS model showed the closest agreement with experimental results at higher frequencies.
• LES performed satisfactorily in reproducing baseline noise.
• Pressure measurements indicated significant loss of turbulent formation coherence.

Conclusions:

• Numerical simulations can reproduce dominant experimental trends in aeroacoustic noise from serrated blades.
• The choice of turbulence model impacts the prediction of acoustic benefits.
• SAS and LES models are promising for analyzing broadband noise in such applications.