Noise reduction analysis of supersonic unheated jets with fluidic injection using large eddy simulations

A set of large eddy simulations is used to perform a numerical analysis of fluidic injection as a tool for noise reduction. This technique, developed at the Pennsylvania State University, allows one to turn on and off the air injectors in order to reduce the noise during takeoff and landing without penalizing performance in other flight regimes. Numerical simulations are performed on a military-style nozzle based on the GE F400-series engines, with a design Mach number of 1.65, for overexpanded jet conditions. The numerical results are compared and validated with the outcome of experiments performed at the Pennsylvania State University. For the case chosen, the fluidic injection shows the potential of breaking down shock cells into smaller structures with different orientation and strength. This directly reduces the intensity of broadband shock associated noise, with a positive effect of reducing the overall sound pressure level by more than [Formula: see text] along the direction of maximum sound propagation of the baseline case. The maximum noise reduction was found to be almost [Formula: see text] at 55° on the azimuthal plane in between two lines of injectors.

Download Full-text

Mechanisms of Jet Noise Reduction and Their Impact on Large-Eddy Simulations (invited)

49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition ◽

10.2514/6.2011-20 ◽

2011 ◽

Cited By ~ 1

Author(s):

Daniel Bodony ◽

Jeonglae Kim ◽

Jonathan Freund

Keyword(s):

Noise Reduction ◽

Jet Noise ◽

Large Eddy Simulations ◽

Large Eddy

Download Full-text

Predicting Cooling Fan Noise of Electric Motor Using Compressible Large Eddy Simulation

Volume 3B: Fluid Applications and Systems ◽

10.1115/ajkfluids2019-4699 ◽

2019 ◽

Author(s):

Kimihisa Kaneko ◽

Tsutomu Yamamoto

Keyword(s):

Mach Number ◽

Large Eddy Simulation ◽

Electric Motor ◽

Pressure Fluctuation ◽

Sound Pressure ◽

Sound Propagation ◽

Rotating Machinery ◽

Eddy Simulation ◽

Large Eddy ◽

Good Agreement

Abstract This paper describes prediction of aeroacoustics from a rotating machinery fan using compressible Large Eddy Simulation (LES). The fan is installed semi-opened space located between the fan cover and the body of rotating machinery such as a electric motor. The fan distributes air from the fan cover intake onto the cooling fins. The Reynolds number of the rotating fan is 9 × 105; its Mach number is approximately 0.1. Under the low Mach number regime, hybrid computational aeroacoustics (hybrid CAA) method, which is solved turbulent flow and acoustics separately, is generally used. However, we used a direct CAA method because interaction between pressure fluctuation from the turbulence and sound propagation should be considered. For the direct CAA method approach, compressible Navier–Stokes equations are solved. Density is calculated from the ideal gas law. To compute turbulence phenomena, LES is used as the turbulence model. The Dynamic Smagorinsky Model is used for the subgrid scale. The sound propagation speed is approximately 10 times faster than the flow speed. Therefore, the numerical schemes, time step, and computational grids size were evaluated with line sound source in the two-dimensional domain as a fundamental study to determine the numerical schemes. Subsequently we evaluated the sound pressure level with the electric motor fan, which is an experimental structure. Through verification of the direct CAA model, we obtained the following results. (1) The predicted pressure fluctuation spectra show good agreement with the experimentally obtained spectra. Specifically, the blade passing frequency (BPF) and trend of the pressure fluctuation decay in the inertial turbulence subrange were predicted. (2) The predicted sound pressure spectra also show good agreement with BPF. Specifically, the acoustic mode and broadband turbulence noise level were predicted.

Download Full-text