The structure of supersonic jet flow and its radiated sound

14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference)

2008

Large-eddy simulations (LES) of a circular supersonic fully expanded jet and an underexpanded jet are performed. Both jets operate at a design Mach number 1.95, and the corresponding fully expanded Mach number for the underexpanded jet is 2.20. Since the simulations do not include the nozzle geometry explicitly, the effects of the inflow conditions (such as the forcing modes and shear layer thickness) on the near field statistics and far field noise are investigated. The near field data are collected from the LES and then the far field noise is computed by the Ffowcs Williams-Hawkings (FWH) surface integral method. The results show that removing the lower forcing modes increases the centerline velocity decay rate, the peak turbulence intensities, and the overall sound pressure level. However, reducing the inflow shear layer thickness has the opposite effect and achieves a better agreement with the experiments in both near field statistics and farfield noise. Similar trends hold for the underexpanded jet in near field statistics; however, the number of shock cells is underpredicted and is insensitive to the inflow conditions. This may be due to contamination by spurious numerical fluctuations caused by the shocks. Further simulations including shock capturing schemes are needed.

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Supersonic Jet Flows and their Noise

14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference)

2008

“…With this idea in mind it is more appropriate to use LES as a tool for jet noise prediction, since it is capable of simulating high Reynolds number flows at a fraction of the cost of DNS. One of the first uses of LES as an investigative tool for jet noise prediction was carried out by Mankbadi et al 4 They performed a simulation of a low Reynolds number supersonic jet and applied Lighthill's analogy 5 to calculate the far-field noise. Lyrintzis and Mankbadi 6 were the first to use Kirchhoff's method with LES to compute the far-field noise.…”

Section: Introductionmentioning

confidence: 99%

Recent Progress of Hot Jet Aeroacoustics using 3-D Large-Eddy Simulation

Lew

11th AIAA/CEAS Aeroacoustics Conference

2005

Improvements in computing speed over the past decade have made Large Eddy Simulation (LES) an attractive tool to study jet noise. In addition, the study of turbulent hot jets for noise prediction is desirable compared to cold/isothermal jets since all jet engines fitted on aircraft operate at hot exhaust conditions. In this regard, we present results for two heated jets with temperature ratios of Tj/T∞ = 1.76 and Tj/T∞ = 2.70, respectively. A computational grid with approximately 4.8 million grid points is used the simulation. Spatial filtering is used as an implicit subgrid scale SGS model in place of the classical Smagorinsky and Dynamic Smagorinsky models. To study the far-field noise, the porous Ffowcs Williams-Hawkings (FWH) surface integral acoustic formulation is employed. The jet development results obtained using our LES methodology are consistent with other LES data and experimental results. The predicted OASPL values for our heated jets follow the trend measured by experiments though our results over-predict by approximately 3dB. Overall, our LES methodology coupled with the Ffowcs Williams-Hawkings aeroacoustics methodology provide satisfactory results.

“…One of the first attempts in using LES as a tool for jet noise prediction was carried out by Mankbadi et al 4 They employed a high-order numerical scheme to perform LES of a supersonic jet flow to capture the time-dependent flow structure and applied Lighthill's theory 5 to calculate the far field noise. The first application of Kirchhoff's method in combination with LES to far field jet noise was conducted by Lyrintzis and Mankbadi.…”

Section: Introductionmentioning

confidence: 99%

3-D Large Eddy Simulation for Jet Aeroacoustics

Uzun

9th AIAA/CEAS Aeroacoustics Conference and Exhibit

2003

We present 3-D Large Eddy Simulation (LES) results for a turbulent isothermal round jet at a Reynolds number of 100,000. Our recently developed LES code is part of a Computational Aeroacoustics (CAA) methodology that couples surface integral acoustics methods with LES for the far field noise estimation of turbulent jets. The LES code employs high-order accurate compact differencing together with implicit spatial filtering and state-of-the-art non-reflecting boundary conditions. A localized dynamic Smagorinsky subgrid-scale (SGS) model is used for representing the effects of the unresolved scales on the resolved scales. A computational grid consisting of 12 million points was used in the present simulation. Mean flow results obtained in our simulation are found to be in excellent agreement with the available experimental data of jets at similar flow conditions. Furthermore, the near field data provided by LES is coupled with the Ffowcs Williams-Hawkings method to compute the far field noise. Far field aeroacoustics results are also presented and comparisons are made with another computational study.